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Combing histogram question

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  • dave doctor
    Hi group, Not sure what s happening here: when I try to stretch a particular fits luminance file in PSCS imported from ccdstack (where it was saved as a 32-bit
    Message 1 of 13 , May 5, 2008
      Hi group,
      Not sure what's happening here: when I try to stretch a particular
      fits luminance file in PSCS imported from ccdstack (where it was saved
      as a 32-bit floating points file), after 4 iterations of curves using
      a typical standard curve with 3 points, the histogram starts to comb
      out while the image is still too dim. However, if I import the file as
      a scaled 16bit TIFF from ccdstack, everything looks great and the
      histogram is perfectly fine. For some reason I can't come close to the
      TIFF result if I start with the raw fits file in PS and try to stretch
      it out with curves.
      Thanks,
      Dave
    • Ron Brant
      If I recall, CS doesn t operate on 32 bit images. I may be wrong on this. ... From: dave doctor To: ccd-newastro@yahoogroups.com Sent: Monday, May 05, 2008
      Message 2 of 13 , May 5, 2008
        If I recall, CS doesn't operate on 32 bit images. I may be wrong on this.

        ----- Original Message -----
        From: dave doctor
        To: ccd-newastro@yahoogroups.com
        Sent: Monday, May 05, 2008 9:37 AM
        Subject: [ccd-newastro] Combing histogram question


        Hi group,
        Not sure what's happening here: when I try to stretch a particular
        fits luminance file in PSCS imported from ccdstack (where it was saved
        as a 32-bit floating points file), after 4 iterations of curves using
        a typical standard curve with 3 points, the histogram starts to comb
        out while the image is still too dim. However, if I import the file as
        a scaled 16bit TIFF from ccdstack, everything looks great and the
        histogram is perfectly fine. For some reason I can't come close to the
        TIFF result if I start with the raw fits file in PS and try to stretch
        it out with curves.
        Thanks,
        Dave





        [Non-text portions of this message have been removed]
      • dave doctor
        Hi Ron, Right. It doesn t, but it still loads in CS as a 16 bit without a prior conversion. Perhaps I need to convert it first? I don t remember having to do
        Message 3 of 13 , May 5, 2008
          Hi Ron,
          Right. It doesn't, but it still loads in CS as a 16 bit without a
          prior conversion. Perhaps I need to convert it first? I don't
          remember having to do that before, but it's been awhile.
          Thanks,
          Dave--- In ccd-newastro@yahoogroups.com, "Ron Brant" <brant.r.d@...>
          wrote:
          >
          > If I recall, CS doesn't operate on 32 bit images. I may be wrong
          on this.
          >
          > ----- Original Message -----
          > From: dave doctor
          > To: ccd-newastro@yahoogroups.com
          > Sent: Monday, May 05, 2008 9:37 AM
          > Subject: [ccd-newastro] Combing histogram question
          >
          >
          > Hi group,
          > Not sure what's happening here: when I try to stretch a
          particular
          > fits luminance file in PSCS imported from ccdstack (where it was
          saved
          > as a 32-bit floating points file), after 4 iterations of curves
          using
          > a typical standard curve with 3 points, the histogram starts to
          comb
          > out while the image is still too dim. However, if I import the
          file as
          > a scaled 16bit TIFF from ccdstack, everything looks great and
          the
          > histogram is perfectly fine. For some reason I can't come close
          to the
          > TIFF result if I start with the raw fits file in PS and try to
          stretch
          > it out with curves.
          > Thanks,
          > Dave
          >
          >
          >
          >
          >
          > [Non-text portions of this message have been removed]
          >
        • Jim Lafferty
          I always save as a 32bit floating point fits file in ccdstak and have had no problem importing into PSCS2 with fits liberator. Jim Jim Lafferty
          Message 4 of 13 , May 5, 2008
            I always save as a 32bit floating point fits file in ccdstak and have had no problem importing into PSCS2 with fits liberator.
            Jim
            Jim Lafferty

            jrlafferty@...
            shogun000@...
            www.scopetrader.com/shogun


            -----Original Message-----
            From: "dave doctor" <glibbins@...>

            Date: Mon, 05 May 2008 17:16:23
            To:ccd-newastro@yahoogroups.com
            Subject: [ccd-newastro] Re: Combing histogram question


            Hi Ron,
            Right. It doesn't, but it still loads in CS as a 16 bit without a
            prior conversion. Perhaps I need to convert it first? I don't
            remember having to do that before, but it's been awhile.
            Thanks,
            Dave--- In ccd-newastro@ <mailto:ccd-newastro%40yahoogroups.com> yahoogroups.com, "Ron Brant" <brant.r.d@...>
            wrote:
            >
            > If I recall, CS doesn't operate on 32 bit images. I may be wrong
            on this.
            >
            > ----- Original Message -----
            > From: dave doctor
            > To: ccd-newastro@ <mailto:ccd-newastro%40yahoogroups.com> yahoogroups.com
            > Sent: Monday, May 05, 2008 9:37 AM
            > Subject: [ccd-newastro] Combing histogram question
            >
            >
            > Hi group,
            > Not sure what's happening here: when I try to stretch a
            particular
            > fits luminance file in PSCS imported from ccdstack (where it was
            saved
            > as a 32-bit floating points file), after 4 iterations of curves
            using
            > a typical standard curve with 3 points, the histogram starts to
            comb
            > out while the image is still too dim. However, if I import the
            file as
            > a scaled 16bit TIFF from ccdstack, everything looks great and
            the
            > histogram is perfectly fine. For some reason I can't come close
            to the
            > TIFF result if I start with the raw fits file in PS and try to
            stretch
            > it out with curves.
            > Thanks,
            > Dave
            >
            >
            >
            >
            >
            > [Non-text portions of this message have been removed]
            >
          • Wodaski - Yahoo
            Whatever you are using to create the TIFF, or to import it into Photoshop (perhaps even PS s own TIFF handler), is not handling the 32-bit data the way you
            Message 5 of 13 , May 5, 2008
              Whatever you are using to create the TIFF, or to import it into Photoshop
              (perhaps even PS's own TIFF handler), is not handling the 32-bit data the
              way you want. It sounds like it is being turned into an 8-bit image, or that
              a conversion to 16-bits is occurring but the conversion is going badly.

              I'm not familiar with moving data from CCDStack, but if someone else doesn't
              have the specific answer you need, the simplest solution is probably to save
              from CCDStack as 16-bit integer, and use Eddie Trimarchi's FitsPlug. If you
              are not yet using Eddie's FitsPlug, it probably would also handle the 32-bit
              FITS data from CCDStack.

              Ron Wodaski

              -----Original Message-----
              From: ccd-newastro@yahoogroups.com [mailto:ccd-newastro@yahoogroups.com] On
              Behalf Of dave doctor
              Sent: Monday, May 05, 2008 10:37 AM
              To: ccd-newastro@yahoogroups.com
              Subject: [ccd-newastro] Combing histogram question

              Hi group,
              Not sure what's happening here: when I try to stretch a particular
              fits luminance file in PSCS imported from ccdstack (where it was saved
              as a 32-bit floating points file), after 4 iterations of curves using
              a typical standard curve with 3 points, the histogram starts to comb
              out while the image is still too dim. However, if I import the file as
              a scaled 16bit TIFF from ccdstack, everything looks great and the
              histogram is perfectly fine. For some reason I can't come close to the
              TIFF result if I start with the raw fits file in PS and try to stretch
              it out with curves.
              Thanks,
              Dave


              ------------------------------------
            • cabissi@comcast.net
              Ron, I can confirm that Fits Plug works fine with the CCDStack 32 bit images. I save in this format from CCDStack and use FitsPlug to load it into PSCS3. This
              Message 6 of 13 , May 5, 2008
                Ron,

                I can confirm that Fits Plug works fine with the CCDStack 32 bit images. I save in this format from CCDStack and use FitsPlug to load it into PSCS3. This takes the 32 bit but, of course you work in 16 bits in PS. When I start seeing the combing start I think that I am overstretching the data. Otherwise it seems to work without any problems as you suggested.

                Chris A.

                -------------- Original message --------------
                From: "Wodaski - Yahoo" <yahoo@...>
                Whatever you are using to create the TIFF, or to import it into Photoshop
                (perhaps even PS's own TIFF handler), is not handling the 32-bit data the
                way you want. It sounds like it is being turned into an 8-bit image, or that
                a conversion to 16-bits is occurring but the conversion is going badly.

                I'm not familiar with moving data from CCDStack, but if someone else doesn't
                have the specific answer you need, the simplest solution is probably to save
                from CCDStack as 16-bit integer, and use Eddie Trimarchi's FitsPlug. If you
                are not yet using Eddie's FitsPlug, it probably would also handle the 32-bit
                FITS data from CCDStack.

                Ron Wodaski

                -----Original Message-----
                From: ccd-newastro@yahoogroups.com [mailto:ccd-newastro@yahoogroups.com] On
                Behalf Of dave doctor
                Sent: Monday, May 05, 2008 10:37 AM
                To: ccd-newastro@yahoogroups.com
                Subject: [ccd-newastro] Combing histogram question

                Hi group,
                Not sure what's happening here: when I try to stretch a particular
                fits luminance file in PSCS imported from ccdstack (where it was saved
                as a 32-bit floating points file), after 4 iterations of curves using
                a typical standard curve with 3 points, the histogram starts to comb
                out while the image is still too dim. However, if I import the file as
                a scaled 16bit TIFF from ccdstack, everything looks great and the
                histogram is perfectly fine. For some reason I can't come close to the
                TIFF result if I start with the raw fits file in PS and try to stretch
                it out with curves.
                Thanks,
                Dave

                ------------------------------------




                [Non-text portions of this message have been removed]
              • Wayne Malkin
                In your original message you stated if I import the file as a scaled 16 bit TIFF... Does that mean you applied some scaling in CCDStack as you saved the
                Message 7 of 13 , May 5, 2008
                  In your original message you stated "if I import the file as a scaled 16
                  bit TIFF..."

                  Does that mean you applied some scaling in CCDStack as you saved the
                  image? If the data you are interested in is in a relatively narrow band of
                  values, you can easily lose dynamic range by converting the unscaled image
                  from floating point to integer values. The decimal places are truncated or
                  rounded, resulting in the combed histogram when you apply curves a few
                  times.

                  Applying even a small amount of non-linear scaling while it is still
                  floating point data will preserve that dynamic range.

                  For example, let's say your data is in the range of 2000 to 2150 counts.
                  Converting that to integer will give you a range of only 150 counts. If
                  the data has one decimal place of significant data, scaling that will
                  preserve the significant fraction.

                  I often use MaximDL and apply a gentle Digital Development filter, without
                  sharpening, before saving. Others I have talked to use FITS Liberator and
                  apply scaling on the import.

                  Wayne







                  "dave doctor" <glibbins@...>
                  Sent by: ccd-newastro@yahoogroups.com
                  05/05/2008 11:16 AM
                  Please respond to
                  ccd-newastro@yahoogroups.com


                  To
                  ccd-newastro@yahoogroups.com
                  cc

                  Subject
                  [ccd-newastro] Re: Combing histogram question









                  Hi Ron,
                  Right. It doesn't, but it still loads in CS as a 16 bit without a
                  prior conversion. Perhaps I need to convert it first? I don't
                  remember having to do that before, but it's been awhile.
                  Thanks,
                  Dave--- In ccd-newastro@yahoogroups.com, "Ron Brant" <brant.r.d@...>
                  wrote:
                  >
                  > If I recall, CS doesn't operate on 32 bit images. I may be wrong
                  on this.
                  >
                  > ----- Original Message -----
                  > From: dave doctor
                  > To: ccd-newastro@yahoogroups.com
                  > Sent: Monday, May 05, 2008 9:37 AM
                  > Subject: [ccd-newastro] Combing histogram question
                  >
                  >
                  > Hi group,
                  > Not sure what's happening here: when I try to stretch a
                  particular
                  > fits luminance file in PSCS imported from ccdstack (where it was
                  saved
                  > as a 32-bit floating points file), after 4 iterations of curves
                  using
                  > a typical standard curve with 3 points, the histogram starts to
                  comb
                  > out while the image is still too dim. However, if I import the
                  file as
                  > a scaled 16bit TIFF from ccdstack, everything looks great and
                  the
                  > histogram is perfectly fine. For some reason I can't come close
                  to the
                  > TIFF result if I start with the raw fits file in PS and try to
                  stretch
                  > it out with curves.
                  > Thanks,
                  > Dave
                  >
                  >
                  >
                  >
                  >
                  > [Non-text portions of this message have been removed]
                  >




                  [Non-text portions of this message have been removed]
                • dave doctor
                  Hi Ron, Thanks for the response. I ll play around with it some more. I am actually using fitsplug already. Regards, Dave--- In ccd-newastro@yahoogroups.com,
                  Message 8 of 13 , May 5, 2008
                    Hi Ron,
                    Thanks for the response. I'll play around with it some more. I am
                    actually using fitsplug already.
                    Regards,
                    Dave--- In ccd-newastro@yahoogroups.com, "Wodaski - Yahoo"
                    <yahoo@...> wrote:
                    >
                    > Whatever you are using to create the TIFF, or to import it into
                    Photoshop
                    > (perhaps even PS's own TIFF handler), is not handling the 32-bit
                    data the
                    > way you want. It sounds like it is being turned into an 8-bit
                    image, or that
                    > a conversion to 16-bits is occurring but the conversion is going
                    badly.
                    >
                    > I'm not familiar with moving data from CCDStack, but if someone
                    else doesn't
                    > have the specific answer you need, the simplest solution is
                    probably to save
                    > from CCDStack as 16-bit integer, and use Eddie Trimarchi's
                    FitsPlug. If you
                    > are not yet using Eddie's FitsPlug, it probably would also handle
                    the 32-bit
                    > FITS data from CCDStack.
                    >
                    > Ron Wodaski
                    >
                    > -----Original Message-----
                    > From: ccd-newastro@yahoogroups.com [mailto:ccd-
                    newastro@yahoogroups.com] On
                    > Behalf Of dave doctor
                    > Sent: Monday, May 05, 2008 10:37 AM
                    > To: ccd-newastro@yahoogroups.com
                    > Subject: [ccd-newastro] Combing histogram question
                    >
                    > Hi group,
                    > Not sure what's happening here: when I try to stretch a particular
                    > fits luminance file in PSCS imported from ccdstack (where it was
                    saved
                    > as a 32-bit floating points file), after 4 iterations of curves
                    using
                    > a typical standard curve with 3 points, the histogram starts to
                    comb
                    > out while the image is still too dim. However, if I import the
                    file as
                    > a scaled 16bit TIFF from ccdstack, everything looks great and the
                    > histogram is perfectly fine. For some reason I can't come close to
                    the
                    > TIFF result if I start with the raw fits file in PS and try to
                    stretch
                    > it out with curves.
                    > Thanks,
                    > Dave
                    >
                    >
                    > ------------------------------------
                    >
                  • Ron Brant
                    I believe that was a difference between CS and CS2. ... From: Jim Lafferty To: Sent: Monday,
                    Message 9 of 13 , May 5, 2008
                      I believe that was a difference between CS and CS2.

                      ----- Original Message -----
                      From: "Jim Lafferty" <jrlafferty@...>
                      To: <ccd-newastro@yahoogroups.com>
                      Sent: Monday, May 05, 2008 10:19 AM
                      Subject: Re: [ccd-newastro] Re: Combing histogram question


                      >I always save as a 32bit floating point fits file in ccdstak and have had
                      >no problem importing into PSCS2 with fits liberator.
                      > Jim
                      > Jim Lafferty
                      >
                      > jrlafferty@...
                      > shogun000@...
                      > www.scopetrader.com/shogun
                      >
                      >
                      > -----Original Message-----
                      > From: "dave doctor" <glibbins@...>
                      >
                      > Date: Mon, 05 May 2008 17:16:23
                      > To:ccd-newastro@yahoogroups.com
                      > Subject: [ccd-newastro] Re: Combing histogram question
                      >
                      >
                      > Hi Ron,
                      > Right. It doesn't, but it still loads in CS as a 16 bit without a
                      > prior conversion. Perhaps I need to convert it first? I don't
                      > remember having to do that before, but it's been awhile.
                      > Thanks,
                      > Dave--- In ccd-newastro@ <mailto:ccd-newastro%40yahoogroups.com>
                      > yahoogroups.com, "Ron Brant" <brant.r.d@...>
                      > wrote:
                      > >
                      > > If I recall, CS doesn't operate on 32 bit images. I may be wrong
                      > on this.
                      > >
                      > > ----- Original Message -----
                      > > From: dave doctor
                      > > To: ccd-newastro@ <mailto:ccd-newastro%40yahoogroups.com>
                      > > yahoogroups.com
                      > > Sent: Monday, May 05, 2008 9:37 AM
                      > > Subject: [ccd-newastro] Combing histogram question
                      > >
                      > >
                      > > Hi group,
                      > > Not sure what's happening here: when I try to stretch a
                      > particular
                      > > fits luminance file in PSCS imported from ccdstack (where it was
                      > saved
                      > > as a 32-bit floating points file), after 4 iterations of curves
                      > using
                      > > a typical standard curve with 3 points, the histogram starts to
                      > comb
                      > > out while the image is still too dim. However, if I import the
                      > file as
                      > > a scaled 16bit TIFF from ccdstack, everything looks great and
                      > the
                      > > histogram is perfectly fine. For some reason I can't come close
                      > to the
                      > > TIFF result if I start with the raw fits file in PS and try to
                      > stretch
                      > > it out with curves.
                      > > Thanks,
                      > > Dave
                      > >
                      > >
                      > >
                      > >
                      > >
                      > > [Non-text portions of this message have been removed]
                      > >
                      >
                      >
                      > ------------------------------------
                      >
                      >
                      >
                      >
                      >
                    • dave doctor
                      Hi Wayne, The scaling is done before the image is saved while in the 32 bit format. CCDstack then allows you to save that in 16bit format preserving the
                      Message 10 of 13 , May 5, 2008
                        Hi Wayne,
                        The scaling is done before the image is saved while in the 32 bit
                        format. CCDstack then allows you to save that in 16bit format
                        preserving the scaling already done as a 'scaled' tiff or you can save
                        as a raw tiff unscaled. The 'scaled' tiff is the version that looks
                        fine in PSCS. The raw tiff combs out. Actually any raw format appears
                        to comb out. I have not tried saving as a 16bit fits (signed or
                        umsigned integer)yet because the program asks you if you want to scale
                        the data again so I'm not sure I want to do that.
                        Regards,
                        Dave--- In ccd-newastro@yahoogroups.com, Wayne Malkin <wmalkin@...> wrote:
                        >
                        > In your original message you stated "if I import the file as a
                        scaled 16
                        > bit TIFF..."
                        >
                        > Does that mean you applied some scaling in CCDStack as you saved the
                        > image? If the data you are interested in is in a relatively narrow
                        band of
                        > values, you can easily lose dynamic range by converting the unscaled
                        image
                        > from floating point to integer values. The decimal places are
                        truncated or
                        > rounded, resulting in the combed histogram when you apply curves a few
                        > times.
                        >
                        > Applying even a small amount of non-linear scaling while it is still
                        > floating point data will preserve that dynamic range.
                        >
                        > For example, let's say your data is in the range of 2000 to 2150
                        counts.
                        > Converting that to integer will give you a range of only 150 counts. If
                        > the data has one decimal place of significant data, scaling that will
                        > preserve the significant fraction.
                        >
                        > I often use MaximDL and apply a gentle Digital Development filter,
                        without
                        > sharpening, before saving. Others I have talked to use FITS
                        Liberator and
                        > apply scaling on the import.
                        >
                        > Wayne
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        > "dave doctor" <glibbins@...>
                        > Sent by: ccd-newastro@yahoogroups.com
                        > 05/05/2008 11:16 AM
                        > Please respond to
                        > ccd-newastro@yahoogroups.com
                        >
                        >
                        > To
                        > ccd-newastro@yahoogroups.com
                        > cc
                        >
                        > Subject
                        > [ccd-newastro] Re: Combing histogram question
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        > Hi Ron,
                        > Right. It doesn't, but it still loads in CS as a 16 bit without a
                        > prior conversion. Perhaps I need to convert it first? I don't
                        > remember having to do that before, but it's been awhile.
                        > Thanks,
                        > Dave--- In ccd-newastro@yahoogroups.com, "Ron Brant" <brant.r.d@>
                        > wrote:
                        > >
                        > > If I recall, CS doesn't operate on 32 bit images. I may be wrong
                        > on this.
                        > >
                        > > ----- Original Message -----
                        > > From: dave doctor
                        > > To: ccd-newastro@yahoogroups.com
                        > > Sent: Monday, May 05, 2008 9:37 AM
                        > > Subject: [ccd-newastro] Combing histogram question
                        > >
                        > >
                        > > Hi group,
                        > > Not sure what's happening here: when I try to stretch a
                        > particular
                        > > fits luminance file in PSCS imported from ccdstack (where it was
                        > saved
                        > > as a 32-bit floating points file), after 4 iterations of curves
                        > using
                        > > a typical standard curve with 3 points, the histogram starts to
                        > comb
                        > > out while the image is still too dim. However, if I import the
                        > file as
                        > > a scaled 16bit TIFF from ccdstack, everything looks great and
                        > the
                        > > histogram is perfectly fine. For some reason I can't come close
                        > to the
                        > > TIFF result if I start with the raw fits file in PS and try to
                        > stretch
                        > > it out with curves.
                        > > Thanks,
                        > > Dave
                        > >
                        > >
                        > >
                        > >
                        > >
                        > > [Non-text portions of this message have been removed]
                        > >
                        >
                        >
                        >
                        >
                        > [Non-text portions of this message have been removed]
                        >
                      • Bill Bradford
                        I have PS CS also and Eddie s Fit Plug and have the same problem. If I convert to 16 bit signed in CCDStack before taking it to PS, I don t see the problem.
                        Message 11 of 13 , May 5, 2008
                          I have PS CS also and Eddie's Fit Plug and have the same problem. If I
                          convert to 16 bit signed in CCDStack before taking it to PS, I don't see the
                          problem.

                          Bill
                          ----- Original Message -----
                          From: "dave doctor" <glibbins@...>
                          To: <ccd-newastro@yahoogroups.com>
                          Sent: Monday, May 05, 2008 1:02 PM
                          Subject: [ccd-newastro] Re: Combing histogram question


                          > Hi Ron,
                          > Thanks for the response. I'll play around with it some more. I am
                          > actually using fitsplug already.
                          > Regards,
                          > Dave--- In ccd-newastro@yahoogroups.com, "Wodaski - Yahoo"
                          > <yahoo@...> wrote:
                          >>
                          >> Whatever you are using to create the TIFF, or to import it into
                          > Photoshop
                          >> (perhaps even PS's own TIFF handler), is not handling the 32-bit
                          > data the
                          >> way you want. It sounds like it is being turned into an 8-bit
                          > image, or that
                          >> a conversion to 16-bits is occurring but the conversion is going
                          > badly.
                          >>
                          >> I'm not familiar with moving data from CCDStack, but if someone
                          > else doesn't
                          >> have the specific answer you need, the simplest solution is
                          > probably to save
                          >> from CCDStack as 16-bit integer, and use Eddie Trimarchi's
                          > FitsPlug. If you
                          >> are not yet using Eddie's FitsPlug, it probably would also handle
                          > the 32-bit
                          >> FITS data from CCDStack.
                          >>
                          >> Ron Wodaski
                          >>
                          >> -----Original Message-----
                          >> From: ccd-newastro@yahoogroups.com [mailto:ccd-
                          > newastro@yahoogroups.com] On
                          >> Behalf Of dave doctor
                          >> Sent: Monday, May 05, 2008 10:37 AM
                          >> To: ccd-newastro@yahoogroups.com
                          >> Subject: [ccd-newastro] Combing histogram question
                          >>
                          >> Hi group,
                          >> Not sure what's happening here: when I try to stretch a particular
                          >> fits luminance file in PSCS imported from ccdstack (where it was
                          > saved
                          >> as a 32-bit floating points file), after 4 iterations of curves
                          > using
                          >> a typical standard curve with 3 points, the histogram starts to
                          > comb
                          >> out while the image is still too dim. However, if I import the
                          > file as
                          >> a scaled 16bit TIFF from ccdstack, everything looks great and the
                          >> histogram is perfectly fine. For some reason I can't come close to
                          > the
                          >> TIFF result if I start with the raw fits file in PS and try to
                          > stretch
                          >> it out with curves.
                          >> Thanks,
                          >> Dave
                          >>
                          >>
                          >> ------------------------------------
                          >>
                          >
                          >
                          >
                          > ------------------------------------
                          >
                          >
                          >
                          >
                        • Bill Bradford
                          Dave, I save as a 16 bit FIT signed and do my own scaling in CCDStack before that. It takes me some trial and error to find the right scaling so that I don t
                          Message 12 of 13 , May 5, 2008
                            Dave,

                            I save as a 16 bit FIT signed and do my own scaling in CCDStack before that.
                            It takes me some trial and error to find the right scaling so that I don't
                            clip the data. I only use a mild amount of scaling and work to get the RGB
                            channels to be scaled so that a combine in PS does not have a bad bias
                            toward a particular color.

                            I no longer have the combed histogram.

                            Bill

                            ----- Original Message -----
                            From: "dave doctor" <glibbins@...>
                            To: <ccd-newastro@yahoogroups.com>
                            Sent: Monday, May 05, 2008 7:12 PM
                            Subject: [ccd-newastro] Re: Combing histogram question


                            > Hi Wayne,
                            > The scaling is done before the image is saved while in the 32 bit
                            > format. CCDstack then allows you to save that in 16bit format
                            > preserving the scaling already done as a 'scaled' tiff or you can save
                            > as a raw tiff unscaled. The 'scaled' tiff is the version that looks
                            > fine in PSCS. The raw tiff combs out. Actually any raw format appears
                            > to comb out. I have not tried saving as a 16bit fits (signed or
                            > umsigned integer)yet because the program asks you if you want to scale
                            > the data again so I'm not sure I want to do that.
                            > Regards,
                            > Dave--- In ccd-newastro@yahoogroups.com, Wayne Malkin <wmalkin@...> wrote:
                            >>
                            >> In your original message you stated "if I import the file as a
                            > scaled 16
                            >> bit TIFF..."
                            >>
                            >> Does that mean you applied some scaling in CCDStack as you saved the
                            >> image? If the data you are interested in is in a relatively narrow
                            > band of
                            >> values, you can easily lose dynamic range by converting the unscaled
                            > image
                            >> from floating point to integer values. The decimal places are
                            > truncated or
                            >> rounded, resulting in the combed histogram when you apply curves a few
                            >> times.
                            >>
                            >> Applying even a small amount of non-linear scaling while it is still
                            >> floating point data will preserve that dynamic range.
                            >>
                            >> For example, let's say your data is in the range of 2000 to 2150
                            > counts.
                            >> Converting that to integer will give you a range of only 150 counts. If
                            >> the data has one decimal place of significant data, scaling that will
                            >> preserve the significant fraction.
                            >>
                            >> I often use MaximDL and apply a gentle Digital Development filter,
                            > without
                            >> sharpening, before saving. Others I have talked to use FITS
                            > Liberator and
                            >> apply scaling on the import.
                            >>
                            >> Wayne
                            >>
                            >>
                            >>
                            >>
                            >>
                            >>
                            >>
                            >> "dave doctor" <glibbins@...>
                            >> Sent by: ccd-newastro@yahoogroups.com
                            >> 05/05/2008 11:16 AM
                            >> Please respond to
                            >> ccd-newastro@yahoogroups.com
                            >>
                            >>
                            >> To
                            >> ccd-newastro@yahoogroups.com
                            >> cc
                            >>
                            >> Subject
                            >> [ccd-newastro] Re: Combing histogram question
                            >>
                            >>
                            >>
                            >>
                            >>
                            >>
                            >>
                            >>
                            >>
                            >> Hi Ron,
                            >> Right. It doesn't, but it still loads in CS as a 16 bit without a
                            >> prior conversion. Perhaps I need to convert it first? I don't
                            >> remember having to do that before, but it's been awhile.
                            >> Thanks,
                            >> Dave--- In ccd-newastro@yahoogroups.com, "Ron Brant" <brant.r.d@>
                            >> wrote:
                            >> >
                            >> > If I recall, CS doesn't operate on 32 bit images. I may be wrong
                            >> on this.
                            >> >
                            >> > ----- Original Message -----
                            >> > From: dave doctor
                            >> > To: ccd-newastro@yahoogroups.com
                            >> > Sent: Monday, May 05, 2008 9:37 AM
                            >> > Subject: [ccd-newastro] Combing histogram question
                            >> >
                            >> >
                            >> > Hi group,
                            >> > Not sure what's happening here: when I try to stretch a
                            >> particular
                            >> > fits luminance file in PSCS imported from ccdstack (where it was
                            >> saved
                            >> > as a 32-bit floating points file), after 4 iterations of curves
                            >> using
                            >> > a typical standard curve with 3 points, the histogram starts to
                            >> comb
                            >> > out while the image is still too dim. However, if I import the
                            >> file as
                            >> > a scaled 16bit TIFF from ccdstack, everything looks great and
                            >> the
                            >> > histogram is perfectly fine. For some reason I can't come close
                            >> to the
                            >> > TIFF result if I start with the raw fits file in PS and try to
                            >> stretch
                            >> > it out with curves.
                            >> > Thanks,
                            >> > Dave
                            >> >
                            >> >
                            >> >
                            >> >
                            >> >
                            >> > [Non-text portions of this message have been removed]
                            >> >
                            >>
                            >>
                            >>
                            >>
                            >> [Non-text portions of this message have been removed]
                            >>
                            >
                            >
                            >
                            > ------------------------------------
                            >
                            >
                            >
                            >
                          • dave doctor
                            Thanks Bill. I ll try that out. Dave ... before that. ... don t ... the RGB ... a few ... counts. If
                            Message 13 of 13 , May 6, 2008
                              Thanks Bill. I'll try that out.
                              Dave
                              --- In ccd-newastro@yahoogroups.com, "Bill Bradford" <bcbradford@...>
                              wrote:
                              >
                              > Dave,
                              >
                              > I save as a 16 bit FIT signed and do my own scaling in CCDStack
                              before that.
                              > It takes me some trial and error to find the right scaling so that I
                              don't
                              > clip the data. I only use a mild amount of scaling and work to get
                              the RGB
                              > channels to be scaled so that a combine in PS does not have a bad bias
                              > toward a particular color.
                              >
                              > I no longer have the combed histogram.
                              >
                              > Bill
                              >
                              > ----- Original Message -----
                              > From: "dave doctor" <glibbins@...>
                              > To: <ccd-newastro@yahoogroups.com>
                              > Sent: Monday, May 05, 2008 7:12 PM
                              > Subject: [ccd-newastro] Re: Combing histogram question
                              >
                              >
                              > > Hi Wayne,
                              > > The scaling is done before the image is saved while in the 32 bit
                              > > format. CCDstack then allows you to save that in 16bit format
                              > > preserving the scaling already done as a 'scaled' tiff or you can save
                              > > as a raw tiff unscaled. The 'scaled' tiff is the version that looks
                              > > fine in PSCS. The raw tiff combs out. Actually any raw format appears
                              > > to comb out. I have not tried saving as a 16bit fits (signed or
                              > > umsigned integer)yet because the program asks you if you want to scale
                              > > the data again so I'm not sure I want to do that.
                              > > Regards,
                              > > Dave--- In ccd-newastro@yahoogroups.com, Wayne Malkin <wmalkin@>
                              wrote:
                              > >>
                              > >> In your original message you stated "if I import the file as a
                              > > scaled 16
                              > >> bit TIFF..."
                              > >>
                              > >> Does that mean you applied some scaling in CCDStack as you saved the
                              > >> image? If the data you are interested in is in a relatively narrow
                              > > band of
                              > >> values, you can easily lose dynamic range by converting the unscaled
                              > > image
                              > >> from floating point to integer values. The decimal places are
                              > > truncated or
                              > >> rounded, resulting in the combed histogram when you apply curves
                              a few
                              > >> times.
                              > >>
                              > >> Applying even a small amount of non-linear scaling while it is still
                              > >> floating point data will preserve that dynamic range.
                              > >>
                              > >> For example, let's say your data is in the range of 2000 to 2150
                              > > counts.
                              > >> Converting that to integer will give you a range of only 150
                              counts. If
                              > >> the data has one decimal place of significant data, scaling that will
                              > >> preserve the significant fraction.
                              > >>
                              > >> I often use MaximDL and apply a gentle Digital Development filter,
                              > > without
                              > >> sharpening, before saving. Others I have talked to use FITS
                              > > Liberator and
                              > >> apply scaling on the import.
                              > >>
                              > >> Wayne
                              > >>
                              > >>
                              > >>
                              > >>
                              > >>
                              > >>
                              > >>
                              > >> "dave doctor" <glibbins@>
                              > >> Sent by: ccd-newastro@yahoogroups.com
                              > >> 05/05/2008 11:16 AM
                              > >> Please respond to
                              > >> ccd-newastro@yahoogroups.com
                              > >>
                              > >>
                              > >> To
                              > >> ccd-newastro@yahoogroups.com
                              > >> cc
                              > >>
                              > >> Subject
                              > >> [ccd-newastro] Re: Combing histogram question
                              > >>
                              > >>
                              > >>
                              > >>
                              > >>
                              > >>
                              > >>
                              > >>
                              > >>
                              > >> Hi Ron,
                              > >> Right. It doesn't, but it still loads in CS as a 16 bit without a
                              > >> prior conversion. Perhaps I need to convert it first? I don't
                              > >> remember having to do that before, but it's been awhile.
                              > >> Thanks,
                              > >> Dave--- In ccd-newastro@yahoogroups.com, "Ron Brant" <brant.r.d@>
                              > >> wrote:
                              > >> >
                              > >> > If I recall, CS doesn't operate on 32 bit images. I may be wrong
                              > >> on this.
                              > >> >
                              > >> > ----- Original Message -----
                              > >> > From: dave doctor
                              > >> > To: ccd-newastro@yahoogroups.com
                              > >> > Sent: Monday, May 05, 2008 9:37 AM
                              > >> > Subject: [ccd-newastro] Combing histogram question
                              > >> >
                              > >> >
                              > >> > Hi group,
                              > >> > Not sure what's happening here: when I try to stretch a
                              > >> particular
                              > >> > fits luminance file in PSCS imported from ccdstack (where it was
                              > >> saved
                              > >> > as a 32-bit floating points file), after 4 iterations of curves
                              > >> using
                              > >> > a typical standard curve with 3 points, the histogram starts to
                              > >> comb
                              > >> > out while the image is still too dim. However, if I import the
                              > >> file as
                              > >> > a scaled 16bit TIFF from ccdstack, everything looks great and
                              > >> the
                              > >> > histogram is perfectly fine. For some reason I can't come close
                              > >> to the
                              > >> > TIFF result if I start with the raw fits file in PS and try to
                              > >> stretch
                              > >> > it out with curves.
                              > >> > Thanks,
                              > >> > Dave
                              > >> >
                              > >> >
                              > >> >
                              > >> >
                              > >> >
                              > >> > [Non-text portions of this message have been removed]
                              > >> >
                              > >>
                              > >>
                              > >>
                              > >>
                              > >> [Non-text portions of this message have been removed]
                              > >>
                              > >
                              > >
                              > >
                              > > ------------------------------------
                              > >
                              > >
                              > >
                              > >
                              >
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