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Re: Possible Sync Issues on A640s

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  • jrn_lng
    Hi Jason You do not say if the cameras use identical exposure values or not. If ISO, aperture and shutter speed are identical, there is probably a calibration
    Message 1 of 12 , Jun 1, 2010
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      Hi Jason

      You do not say if the cameras use identical exposure values or not. If ISO, aperture and shutter speed are identical, there is probably a calibration problem.

      If your cameras choose different exposure values, there are a few camera settings that may improve your results. The different exposure should not cause synch problems, but may still cause useless pictures, for instance if one image shows more motion blur than the other.

      If you want to be certain that all camera settings are the same you can use the "reset all" in the Canon setup menu, and start from scratch.

      Make sure to turn off face recognition if left camera is upside down

      The cameras will usually link focus point and exposure, so if the cameras select different focus points, this may cause different exposure values. If your cameras allow selecting centre focus, that is a good start. You probably will have to be in some manual mode for this (M,P,A,S or such).

      Still the cameras will link focus and exposure, and your cameras may still be getting different exposure values. Setting light metering to average may help. I usually get better results with average metering on my ixus860 rig.

      Set the same ISO speed on both cameras, not auto ISO.

      Usually a little difference in shutter speed does not matter, like 1/250 on one camera and 1/320 on the other, since it will usually be quick enough to freeze slow objects with both. But, for instance with night shots with moving cars, the slightest difference in shutter speed may ruin the stereo pair. In such situations full manual control may be your best option.

      You could also check in your Canon user manual if your camera has got exposure lock, which may sometimes be more convenient than using full manual. (Even works with ixus860). For instance in aperture priority mode you will get an auto-shutter speed which you can lock on one camera, and then check and lock the other. You may have to point the other camera to more or less light in the scene to get the right shutter speed.

      Let us know if this helps.

      regards,
      Jørn




      --- In StereoDataMaker@yahoogroups.com, jsordaz@... wrote:
      >
      > Greetings,
      >
      > I've successfully installed SDM on my 2 A640s and everything seems to be working fine except I may be having an issue with syncing...maybe.
      >
      > All of the settings, Canon OS and SDM, are exactly the same as far as I can tell. I primarily shoot in AV mode. The issue lies in the fact that one of cameras seems to be usually by off by 1/3 of a stop (usually less exposure). I've increased the manual exposure override to plus 1/3 of a stop and visually they seem to be closer. That said, I wonder if this might be a common issue due to the nature lenses and what not.
      >
      > Question: Will this cause a syncing issue?
      >
      > I'd appreciate hearing you experiences and thoughts, and thanks in advance,
      >
      > Jason
      > Santa Fe, NM
      >
      > ps. I've posted a few pics of my rig and one of the first test shots (anaglyph). See my album here or on Flickr:
      > http://groups.yahoo.com/group/StereoDataMaker/photos/album/1577280340/pic/list
      > http://www.flickr.com/photos/themusicoflife/sets/72157624161765316/detail/
      >
    • jsordaz@gmail.com
      Hi, Thank you for your replies, I appreciate that. I apologize for not providing more information about the camera setups. Before writing to the forum about
      Message 2 of 12 , Jun 1, 2010
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        Hi,

        Thank you for your replies, I appreciate that. I apologize for not providing more information about the camera setups. Before writing to the forum about this particular situation I reset the Canon and SDM software after which I set identical settings on both A640s (fixed ISO [e.g. ISO 80], same aperture values, no exposure compensation, fixed center metering). One of the lenses seems sorta hazy and I'm thinking that is the reason why that camera usually records slightly more exposure (1/3 of a stop).

        I will delve deeper into the Canon settings, as you suggested, to see if I can resolve the issue. I'll report back.

        Again, many thanks,

        Jason
      • jrn_lng
        ... Are the shutter speeds the same, or is one image just brighter? Jørn
        Message 3 of 12 , Jun 1, 2010
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          --- In StereoDataMaker@yahoogroups.com, jsordaz@... wrote:

          > the reason why that camera usually records slightly more exposure (1/3 of a stop).

          Are the shutter speeds the same, or is one image just brighter?

          Jørn
        • jsordaz@gmail.com
          ... Hi Jørn, the shutter speeds are not the same and yes one image is usually a tad brighter.
          Message 4 of 12 , Jun 1, 2010
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            > Are the shutter speeds the same, or is one image just brighter?

            Hi Jørn, the shutter speeds are not the same and yes one image is
            usually a tad brighter.
          • rexlion22
            Linked focus and exposure... is this a newer feature of SDM that I was not aware of? I thought it only controls timing of the shutters so they fire in sync,
            Message 5 of 12 , Jun 1, 2010
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              Linked focus and exposure... is this a newer feature of SDM that I was not aware of? I thought it only controls timing of the shutters so they fire in sync, but each camera controls its own focusing and exposure readings.

              Mike G.


              =======================================
              --- In StereoDataMaker@yahoogroups.com, "jrn_lng" <jrn_lng@...> wrote:
              > ....
              > The cameras will usually link focus point and exposure, so if the cameras select different focus points, this may cause different exposure values. If your cameras allow selecting centre focus, that is a good start. You probably will have to be in some manual mode for this (M,P,A,S or such).
              >
              > Still the cameras will link focus and exposure...
              > Jørn
            • jrn_lng
              ... Linked focus and exposure is within each camera, not linked between the two cameras. This is not an SDM feature, but a camera feature. From Canon s web
              Message 6 of 12 , Jun 1, 2010
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                --- In StereoDataMaker@yahoogroups.com, "rexlion22" <3Dslides@...> wrote:
                >
                > Linked focus and exposure... is this a newer feature of SDM that I was not aware of? I thought it only controls timing of the shutters so they fire in sync, but each camera controls its own focusing and exposure readings.
                >
                > Mike G.


                Linked focus and exposure is within each camera, not linked between the two cameras. This is not an SDM feature, but a camera feature.

                From Canon's web site:

                Evaluative: Metering is directly linked to, and concentrated on, the active Autofocus (AF) point. Light values measured at the active AF point are compared with light values measured from the metering segments surrounding the active point, and the camera's metering system attempts to provide an accurate exposure based on that comparison.

                http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=2666
                or
                http://tinyurl.com/bd49y6

                Jørn
              • Michael
                if the camera has exposure-lock, how can this be used with twin-cams? I dont see AE-lock in my a590is. i can lock exposure by half-press. the same with first
                Message 7 of 12 , Jun 2, 2010
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                  if the camera has exposure-lock, how can this be used with twin-cams?
                  I dont see AE-lock in my a590is. i can lock exposure by half-press. the same with first sdm-switch-press. by adjusting both seems impossible.
                  Thats why i always find a way to fix exposure.

                  The question is now multifield or average? Spot does not seem to be good. Maybe for only one camera. But how to synch the second cam if it does not point to the same subject. For such problems i am almost always use manual mode. Biggest Problem i once had was Safety MF(Manual Focus) which can overrule Manual Focus if Cam sees a subject in the focus-frame. It can be turned off.
                  Michael P.
                • jsordaz@gmail.com
                  Greetings, So after checking, and rechecking, all of the Canon and SDM settings I can find NO software differences between the two cameras. The reason why I
                  Message 8 of 12 , Jun 3, 2010
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                    Greetings,

                    So after checking, and rechecking, all of the Canon and SDM settings I can find NO software differences between the two cameras.  The reason why I have different exposure values between cameras must have to do with that fact that one lens is a tad "cloudy" and therefore causing 1/3 more exposure than the other camera. Still, with that exposure difference I have not noticed any sync issues, though in the shots referenced below the syncing was right on (issues with sync seem to be hit or miss).

                    See these shots (left cam=f2.8, 1/250, ISO 80, focal length 7.3mm/right cam=f2.8, 1/250, ISO 80, focal length 7.3mm):

                    From now on, with this A640 rig, I will either shoot in Manual or Aperture Priority mode.

                    Thank you to all who contributed to this question!

                    Jason Ordaz
                    Santa Fe, New Mexico
                  • microfunguy
                    ... Well, it is impossible to tell from those images ... but you will not. Synch only depends on your switch working properly. The little boy is looking very
                    Message 9 of 12 , Jun 3, 2010
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                      Jason wrote:

                      >I may be having an issue with syncing...maybe.

                      Well, it is impossible to tell from those images ... but you will not.

                      Synch only depends on your switch working properly.

                      The little boy is looking very serious :-)



                      David
                    • rexlion22
                      Exposure variations are pretty common between cameras. You might clean the lenses and sensor openings to see if that helps. But why fret about it? If the
                      Message 10 of 12 , Jun 3, 2010
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                        Exposure variations are pretty common between cameras. You might clean the lenses and sensor openings to see if that helps. But why fret about it? If the exposure difference is consistent, you can adjust one camera up or down in 1/3 stop increments. Or, some models allow manual settings, get exactly what you want on both cams. And if that isn't good enough, SPM will adjust the right image to match the left (you can get vice versa by switching sides, just hit the parallel/cross button before adjustment) with a click of the mouse. Exposure differences in twin rigs were a really big deal with film cameras, but not with digital rigs. And exposure is not a sync issue at all, BTW.

                        Mike G.



                        --- In StereoDataMaker@yahoogroups.com, jsordaz@... wrote:
                        >
                        > Greetings,
                        > So after checking, and rechecking, all of the Canon and SDM settings I
                        > can find NO software differences between the two cameras. The reason
                        > why I have different exposure values between cameras must have to do
                        > with that fact that one lens is a tad "cloudy" and therefore causing 1/3
                        > more exposure than the other camera...
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