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Where are my smooth levels going?

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  • richsmith79
    I keep running into a problem processing my images. I start out with what looks like a nice smooth image, and as soon as I start stretching it, the histogram
    Message 1 of 9 , Nov 24, 2009
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      I keep running into a problem processing my images. I start out with what looks like a nice smooth image, and as soon as I start stretching it, the histogram starts looking like a picket fence (i.e., spikes) and the image goes from smooth to just a few discrete intensity levels. I'm supposedly working with 16 bits per pixel, but it quickly looks like it goes to about 5 or 6 bits per pixel after only a few very modest stretches. What am I doing wrong?

      Any thoughts would be very welcome. Thanks.

      Rich
    • Wodaski - Yahoo
      Are you in Photoshop? You are right - that sounds like it is NOT a 16-bit file. Look at each step you are doing - is anything converting you to an 8-bit image?
      Message 2 of 9 , Nov 24, 2009
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        Are you in Photoshop?

        You are right - that sounds like it is NOT a 16-bit file. Look at each step you are doing - is anything converting you to an 8-bit image?

        For example, saving to a TIFF in CCDSoft would, if memory serves, give you an 8-bit file.

        You need to examine every step of your process and see if any part of it is turning your data into an 8-bit image.

        Ron W

        On Nov 24, 2009, at 3:35 PM, richsmith79 wrote:

        > I keep running into a problem processing my images. I start out with what looks like a nice smooth image, and as soon as I start stretching it, the histogram starts looking like a picket fence (i.e., spikes) and the image goes from smooth to just a few discrete intensity levels. I'm supposedly working with 16 bits per pixel, but it quickly looks like it goes to about 5 or 6 bits per pixel after only a few very modest stretches. What am I doing wrong?
        >
        > Any thoughts would be very welcome. Thanks.
        >
        > Rich
        >
        >
        >
        > ------------------------------------
        >
        >
        >
        >
      • Paul Beskeen
        ... what looks like a nice smooth image, and as soon as I start stretching it, the histogram starts looking like a picket fence (i.e., spikes) and the image
        Message 3 of 9 , Nov 25, 2009
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          richsmith79 wrote:
          > I keep running into a problem processing my images. I start out with
          what looks like a nice smooth image, and as soon as I start stretching
          it, the histogram starts looking like a picket fence (i.e., spikes) and
          the image goes from smooth to just a few discrete intensity levels. I'm
          supposedly working with 16 bits per pixel, but it quickly looks like it
          goes to about 5 or 6 bits per pixel after only a few very modest
          stretches. What am I doing wrong?
          >
          > Any thoughts would be very welcome. Thanks.

          If you are using adjustment layers then this is normal. When you merge
          the layers you will get a smooth histogram again. Another way to get the
          histogram smooth temporarily is to hit the recache button on the top
          right of the histogram dialog.

          If you are not using adjustment layers then you may be doing too many
          odd stretches that pull the histogram apart, or perhaps you have
          inadvertently imported as eight bit data.

          Cheers, Paul.
          --
        • richsmith79
          Ron and Paul, Thanks for the input. I ve been saving everything as 16 bit files in both FIT and TIFF format, with similar results. I don t seem to have an
          Message 4 of 9 , Nov 25, 2009
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            Ron and Paul,

            Thanks for the input. I've been saving everything as 16 bit files in both FIT and TIFF format, with similar results. I don't seem to have an issue when I save the files as separate R, G and B files in Nebulosity. Each greyscale image file looks very smooth.

            After doing some additional experiments, I think I have a PhotoShop problem. In at least one case, as soon as I zoom a 16-bit RGB TIFF image created with Nebulosity below 50%, the displayed image goes from very smooth to something that looks like it has 4 bits per pixel. Very odd. But in another case, zoom has no affect on the blockiness of a 16-bit RGB TIFF image created with Deep Sky Stacker. Using FITS Liberator to create 16 bit files also creates blocky images.

            I'm confused.

            --- In ccd-newastro@yahoogroups.com, Paul Beskeen <yahoo@...> wrote:
            >
            > richsmith79 wrote:
            > > I keep running into a problem processing my images. I start out with
            > what looks like a nice smooth image, and as soon as I start stretching
            > it, the histogram starts looking like a picket fence (i.e., spikes) and
            > the image goes from smooth to just a few discrete intensity levels. I'm
            > supposedly working with 16 bits per pixel, but it quickly looks like it
            > goes to about 5 or 6 bits per pixel after only a few very modest
            > stretches. What am I doing wrong?
            > >
            > > Any thoughts would be very welcome. Thanks.
            >
            > If you are using adjustment layers then this is normal. When you merge
            > the layers you will get a smooth histogram again. Another way to get the
            > histogram smooth temporarily is to hit the recache button on the top
            > right of the histogram dialog.
            >
            > If you are not using adjustment layers then you may be doing too many
            > odd stretches that pull the histogram apart, or perhaps you have
            > inadvertently imported as eight bit data.
            >
            > Cheers, Paul.
            > --
            >
          • Adam Block
            There is something else- but I don t want to confuse the matter- so ignore this if it is not relevant. You can get the effect you describe when saving 16-bit
            Message 5 of 9 , Nov 25, 2009
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              There is something else- but I don't want to confuse the matter- so ignore this if it is not relevant.

              You can get the effect you describe when saving 16-bit INTEGER TIF files for Photoshop. The original floating point file that you have created (presumably in Maxim DL or CCDStack...etc) contains fractional values (values to the right of the decimal). These fractional values are dropped in the creation of the 16-bit integer TIF.

              This quantization artifact sometimes happens for me when dealing with Ha data since the range of values is so small those fractional values can make a difference. Scaling data (by multiplying by some reasonable number) before saving as a 16-bit (integer) file can help pull some of those fractional values to be expressed in the integer file.

              Nowadays if I am blending Ha data this happens naturally for me when I normalize the Ha data to the luminance or Red information.

              Anyway, just felt like babbling a little bit.
              Adam


              ------------------------------------------------------------
              Adam Block

              ngc1535@...

              http://skycenter.arizona.edu (NEW!)

              http://caelumobservatory.com/

              Caelum videre iussit, et erectos ad sidera tollere vultus.
              He bid them look at the sky and lift their faces to the stars.
              --Ovid, Metamorphoses 1. 85-8

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


               

               

              *-----Original Message-----
              *From: richsmith79 [mailto:smithrb@...]
              *Sent: Tuesday, November 24, 2009 03:35 PM
              *To: ccd-newastro@yahoogroups.com
              *Subject: [ccd-newastro] Where are my smooth levels going?
              *
              *I keep running into a problem processing my images. I start out with what looks like a nice smooth image, and as soon as I start stretching it, the histogram starts looking like a picket fence (i.e., spikes) and the image goes from smooth to just a few discrete intensity levels. I'm supposedly working with 16 bits per pixel, but it quickly looks like it goes to about 5 or 6 bits per pixel after only a few very modest stretches. What am I doing wrong?
              *
              *Any thoughts would be very welcome. Thanks.
              *
              *Rich
              *
              *
            • Larry Phillips
              Adam, sounds like a topic for a future tutorial. Larry
              Message 6 of 9 , Nov 26, 2009
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                Adam, sounds like a topic for a future tutorial.

                Larry


                --- In ccd-newastro@yahoogroups.com, "Adam Block" <ngc1535@...> wrote:
                >
                > There is something else- but I don't want to confuse the matter- so ignore this if it is not relevant.
                >
                > You can get the effect you describe when saving 16-bit INTEGER TIF files for Photoshop. The original floating point file that you have created (presumably in Maxim DL or CCDStack...etc) contains fractional values (values to the right of the decimal). These fractional values are dropped in the creation of the 16-bit integer TIF.
                >
                > This quantization artifact sometimes happens for me when dealing with Ha data since the range of values is so small those fractional values can make a difference. Scaling data (by multiplying by some reasonable number) before saving as a 16-bit (integer) file can help pull some of those fractional values to be expressed in the integer file.
                >
                > Nowadays if I am blending Ha data this happens naturally for me when I normalize the Ha data to the luminance or Red information.
                >
                > Anyway, just felt like babbling a little bit.
                > Adam
                >
                >
                > ------------------------------------------------------------
                > Adam Block
                >
                > ngc1535@...
                >
                > http://skycenter.arizona.edu (NEW!)
                >
                > http://caelumobservatory.com/
                >
                > Caelum videre iussit, et erectos ad sidera tollere vultus.
                > He bid them look at the sky and lift their faces to the stars.
                > --Ovid, Metamorphoses 1. 85-8
                >
                > ------------------------------------------------------------
                >
                >
                >  
                >
                >  
                >
                > *-----Original Message-----
                > *From: richsmith79 [mailto:smithrb@...]
                > *Sent: Tuesday, November 24, 2009 03:35 PM
                > *To: ccd-newastro@yahoogroups.com
                > *Subject: [ccd-newastro] Where are my smooth levels going?
                > *
                > *I keep running into a problem processing my images. I start out with what looks like a nice smooth image, and as soon as I start stretching it, the histogram starts looking like a picket fence (i.e., spikes) and the image goes from smooth to just a few discrete intensity levels. I'm supposedly working with 16 bits per pixel, but it quickly looks like it goes to about 5 or 6 bits per pixel after only a few very modest stretches. What am I doing wrong?
                > *
                > *Any thoughts would be very welcome. Thanks.
                > *
                > *Rich
                > *
                > *
                >
              • richsmith79
                Adam, you were not babbling at all. You hit the nail on the head and solved my problem. Thanks so much. Rich
                Message 7 of 9 , Nov 27, 2009
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                  Adam, you were not babbling at all. You hit the nail on the head and solved my problem. Thanks so much.

                  Rich

                  --- In ccd-newastro@yahoogroups.com, "Adam Block" <ngc1535@...> wrote:
                  >
                  > There is something else- but I don't want to confuse the matter- so ignore this if it is not relevant.
                  >
                  > You can get the effect you describe when saving 16-bit INTEGER TIF files for Photoshop. The original floating point file that you have created (presumably in Maxim DL or CCDStack...etc) contains fractional values (values to the right of the decimal). These fractional values are dropped in the creation of the 16-bit integer TIF.
                  >
                  > This quantization artifact sometimes happens for me when dealing with Ha data since the range of values is so small those fractional values can make a difference. Scaling data (by multiplying by some reasonable number) before saving as a 16-bit (integer) file can help pull some of those fractional values to be expressed in the integer file.
                  >
                  > Nowadays if I am blending Ha data this happens naturally for me when I normalize the Ha data to the luminance or Red information.
                  >
                  > Anyway, just felt like babbling a little bit.
                  > Adam
                  >
                  >
                  > ------------------------------------------------------------
                  > Adam Block
                  >
                  > ngc1535@...
                  >
                  > http://skycenter.arizona.edu (NEW!)
                  >
                  > http://caelumobservatory.com/
                  >
                  > Caelum videre iussit, et erectos ad sidera tollere vultus.
                  > He bid them look at the sky and lift their faces to the stars.
                  > --Ovid, Metamorphoses 1. 85-8
                  >
                  > ------------------------------------------------------------
                  >
                  >
                  >  
                  >
                  >  
                  >
                  > *-----Original Message-----
                  > *From: richsmith79 [mailto:smithrb@...]
                  > *Sent: Tuesday, November 24, 2009 03:35 PM
                  > *To: ccd-newastro@yahoogroups.com
                  > *Subject: [ccd-newastro] Where are my smooth levels going?
                  > *
                  > *I keep running into a problem processing my images. I start out with what looks like a nice smooth image, and as soon as I start stretching it, the histogram starts looking like a picket fence (i.e., spikes) and the image goes from smooth to just a few discrete intensity levels. I'm supposedly working with 16 bits per pixel, but it quickly looks like it goes to about 5 or 6 bits per pixel after only a few very modest stretches. What am I doing wrong?
                  > *
                  > *Any thoughts would be very welcome. Thanks.
                  > *
                  > *Rich
                  > *
                  > *
                  >
                • astromfm
                  Adam, I echo the comment below. I ve been struggling with processing the Iris Nebula, which also has a narrow range of values in the dim zone. I was also
                  Message 8 of 9 , Dec 3, 2009
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                    Adam, I echo the comment below. I've been struggling with processing the Iris Nebula, which also has a narrow range of values in the dim zone. I was also wondering why my histograms were turning into "picket fences" in PhotoShop, and actually posted that question to a different group. Your explanation helped me to find a solution, I think. I save from DeepSkyStacker in 32bit/channel TIFF rational format then import this into PhotoShop CS2. Before I convert it to 16bit/channel, I apply a mild Astra Image - Digital Development Process stretch (I found out by accident that the Astra Image plugin will work on 32bit images in PS), then I convert to 16bits/channel and process with levels and curves as usual. My dynamic range is much better after doing this, I think because the DDP stretch increases the dynamic range before converting to 16bit/channel (but please feel free to set me straight if this makes no sense, I'm no expert on PS!) and the "picket fences" are now much smoother histograms. Seems to work, and the quick process I did on the Iris showed MUCH more detail in the dim regions -- I'm seeing all sorts of detail in the dust clouds that I had no idea was there. Time to do a full reprocess...(again)...

                    thanks for the tip,
                    Keith

                    P.S. I bought a copy of your most recent video as a "Christmas present" to me from my wife. I'm looking forward to learning more PS tips -- does the learning curve ever start to level off?

                    --- In ccd-newastro@yahoogroups.com, "richsmith79" <smithrb@...> wrote:
                    >
                    > Adam, you were not babbling at all. You hit the nail on the head and solved my problem. Thanks so much.
                    >
                    > Rich
                    >
                    > --- In ccd-newastro@yahoogroups.com, "Adam Block" <ngc1535@> wrote:
                    > >
                    > > There is something else- but I don't want to confuse the matter- so ignore this if it is not relevant.
                    > >
                    > > You can get the effect you describe when saving 16-bit INTEGER TIF files for Photoshop. The original floating point file that you have created (presumably in Maxim DL or CCDStack...etc) contains fractional values (values to the right of the decimal). These fractional values are dropped in the creation of the 16-bit integer TIF.
                    > >
                    > > This quantization artifact sometimes happens for me when dealing with Ha data since the range of values is so small those fractional values can make a difference. Scaling data (by multiplying by some reasonable number) before saving as a 16-bit (integer) file can help pull some of those fractional values to be expressed in the integer file.
                    > >
                    > > Nowadays if I am blending Ha data this happens naturally for me when I normalize the Ha data to the luminance or Red information.
                    > >
                    > > Anyway, just felt like babbling a little bit.
                    > > Adam
                    > >
                    > >
                    > > ------------------------------------------------------------
                    > > Adam Block
                    > >
                    > > ngc1535@
                    > >
                    > > http://skycenter.arizona.edu (NEW!)
                    > >
                    > > http://caelumobservatory.com/
                    > >
                    > > Caelum videre iussit, et erectos ad sidera tollere vultus.
                    > > He bid them look at the sky and lift their faces to the stars.
                    > > --Ovid, Metamorphoses 1. 85-8
                    > >
                    > > ------------------------------------------------------------
                    > >
                    > >
                    > >  
                    > >
                    > >  
                    > >
                    > > *-----Original Message-----
                    > > *From: richsmith79 [mailto:smithrb@]
                    > > *Sent: Tuesday, November 24, 2009 03:35 PM
                    > > *To: ccd-newastro@yahoogroups.com
                    > > *Subject: [ccd-newastro] Where are my smooth levels going?
                    > > *
                    > > *I keep running into a problem processing my images. I start out with what looks like a nice smooth image, and as soon as I start stretching it, the histogram starts looking like a picket fence (i.e., spikes) and the image goes from smooth to just a few discrete intensity levels. I'm supposedly working with 16 bits per pixel, but it quickly looks like it goes to about 5 or 6 bits per pixel after only a few very modest stretches. What am I doing wrong?
                    > > *
                    > > *Any thoughts would be very welcome. Thanks.
                    > > *
                    > > *Rich
                    > > *
                    > > *
                    > >
                    >
                  • richsmith79
                    I ve been saving in 32 Bit Integer FIT format and doing an initial stretch with Fits Liberator when opening in PS. Getting really good results now. Thanks
                    Message 9 of 9 , Dec 4, 2009
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                      I've been saving in 32 Bit Integer FIT format and doing an initial stretch with Fits Liberator when opening in PS. Getting really good results now. Thanks again.

                      Rich

                      --- In ccd-newastro@yahoogroups.com, "astromfm" <eggerk@...> wrote:
                      >
                      > Adam, I echo the comment below. I've been struggling with processing the Iris Nebula, which also has a narrow range of values in the dim zone. I was also wondering why my histograms were turning into "picket fences" in PhotoShop, and actually posted that question to a different group. Your explanation helped me to find a solution, I think. I save from DeepSkyStacker in 32bit/channel TIFF rational format then import this into PhotoShop CS2. Before I convert it to 16bit/channel, I apply a mild Astra Image - Digital Development Process stretch (I found out by accident that the Astra Image plugin will work on 32bit images in PS), then I convert to 16bits/channel and process with levels and curves as usual. My dynamic range is much better after doing this, I think because the DDP stretch increases the dynamic range before converting to 16bit/channel (but please feel free to set me straight if this makes no sense, I'm no expert on PS!) and the "picket fences" are now much smoother histograms. Seems to work, and the quick process I did on the Iris showed MUCH more detail in the dim regions -- I'm seeing all sorts of detail in the dust clouds that I had no idea was there. Time to do a full reprocess...(again)...
                      >
                      > thanks for the tip,
                      > Keith
                      >
                      > P.S. I bought a copy of your most recent video as a "Christmas present" to me from my wife. I'm looking forward to learning more PS tips -- does the learning curve ever start to level off?
                      >
                      > --- In ccd-newastro@yahoogroups.com, "richsmith79" <smithrb@> wrote:
                      > >
                      > > Adam, you were not babbling at all. You hit the nail on the head and solved my problem. Thanks so much.
                      > >
                      > > Rich
                      > >
                      > > --- In ccd-newastro@yahoogroups.com, "Adam Block" <ngc1535@> wrote:
                      > > >
                      > > > There is something else- but I don't want to confuse the matter- so ignore this if it is not relevant.
                      > > >
                      > > > You can get the effect you describe when saving 16-bit INTEGER TIF files for Photoshop. The original floating point file that you have created (presumably in Maxim DL or CCDStack...etc) contains fractional values (values to the right of the decimal). These fractional values are dropped in the creation of the 16-bit integer TIF.
                      > > >
                      > > > This quantization artifact sometimes happens for me when dealing with Ha data since the range of values is so small those fractional values can make a difference. Scaling data (by multiplying by some reasonable number) before saving as a 16-bit (integer) file can help pull some of those fractional values to be expressed in the integer file.
                      > > >
                      > > > Nowadays if I am blending Ha data this happens naturally for me when I normalize the Ha data to the luminance or Red information.
                      > > >
                      > > > Anyway, just felt like babbling a little bit.
                      > > > Adam
                      > > >
                      > > >
                      > > > ------------------------------------------------------------
                      > > > Adam Block
                      > > >
                      > > > ngc1535@
                      > > >
                      > > > http://skycenter.arizona.edu (NEW!)
                      > > >
                      > > > http://caelumobservatory.com/
                      > > >
                      > > > Caelum videre iussit, et erectos ad sidera tollere vultus.
                      > > > He bid them look at the sky and lift their faces to the stars.
                      > > > --Ovid, Metamorphoses 1. 85-8
                      > > >
                      > > > ------------------------------------------------------------
                      > > >
                      > > >
                      > > >  
                      > > >
                      > > >  
                      > > >
                      > > > *-----Original Message-----
                      > > > *From: richsmith79 [mailto:smithrb@]
                      > > > *Sent: Tuesday, November 24, 2009 03:35 PM
                      > > > *To: ccd-newastro@yahoogroups.com
                      > > > *Subject: [ccd-newastro] Where are my smooth levels going?
                      > > > *
                      > > > *I keep running into a problem processing my images. I start out with what looks like a nice smooth image, and as soon as I start stretching it, the histogram starts looking like a picket fence (i.e., spikes) and the image goes from smooth to just a few discrete intensity levels. I'm supposedly working with 16 bits per pixel, but it quickly looks like it goes to about 5 or 6 bits per pixel after only a few very modest stretches. What am I doing wrong?
                      > > > *
                      > > > *Any thoughts would be very welcome. Thanks.
                      > > > *
                      > > > *Rich
                      > > > *
                      > > > *
                      > > >
                      > >
                      >
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