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Photo Forum / Digital Photography / DSLR Cameras / August 200520D and ISO 3200
I am wondering why Canon made 3200 a special function. Does that make sense?  SignatureMark Photos, Ideas & Opinions http://www.marklauter.com > I am wondering why Canon made 3200 a special function. Does that make > sense? Hi Beach Bum, My guess is: to make people think about it before using it. Canon have probably made some compromises to get such high gain. -Mike "Mike Warren" <miwa-not-this-bit@or-this-cairnscarsound.com.au> wrote in message n > > I am wondering why Canon made 3200 a special function. Does that make > > sense? > > Hi Beach Bum, Hi Mike, small world. :) > My guess is: to make people think about it before using it. > Canon have probably made some compromises to get > such high gain. Like a sort of built in disclaimer I guess. FWIW, the noise at 3200 is about the same as my F717 was at 800. The noise at 1600 is like the 717 at 100. SignatureMark Photos, Ideas & Opinions http://www.marklauter.com >Like a sort of built in disclaimer I guess. FWIW, the noise at 3200 is >about the same as my F717 was at 800. The noise at 1600 is like the 717 at >100. I have the 20D and F707, which has the same sensor as the F717, and I'd say the 20D's 1600 is about as noisy as the F707 would be if it had an ISO 250. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > >Like a sort of built in disclaimer I guess. FWIW, the noise at 3200 is > >about the same as my F717 was at 800. The noise at 1600 is like the 717 at [quoted text clipped - 3 lines] > say the 20D's 1600 is about as noisy as the F707 would be if it had an > ISO 250. It's probably one of those YMMV things. I had a lot of trouble with the 717 - 4 times to the warranty repair shop for major failures. I think mine was made on Monday. SignatureMark Photos, Ideas & Opinions http://www.marklauter.com > I am wondering why Canon made 3200 a special function. Does that make > sense? Yes, because it's the only ISO setting not actually based on analog gain. It's just ISO1600 with the final RAW values doubled, and the only time you ever want to use it is when you're shooting straight to JPG. If you're shooting to RAW (which the 20D is based around), don't go above 1600, and just use the EC in the raw converter to get the same effect with more control. SignatureZed Pobre <zed@resonant.org> a.k.a. Zed Pobre <zed@debian.org> PGP key and fingerprint available on finger; encrypted mail welcomed. > > I am wondering why Canon made 3200 a special function. Does that make > > sense? [quoted text clipped - 7 lines] > above 1600, and just use the EC in the raw converter to get the same > effect with more control. Ah hah! Thanks for that info. I'll explore RAW in a few weeks. SignatureMark Photos, Ideas & Opinions http://www.marklauter.com >> I am wondering why Canon made 3200 a special function. Does that make >> sense? > >Yes, because it's the only ISO setting not actually based on analog >gain. I dopn't think that's the reason, though, as the 10D's 1600 isn't hidden, and is pushed 800. >It's just ISO1600 with the final RAW values doubled, and the >only time you ever want to use it is when you're shooting straight to >JPG. Another possibility is that you've decided that you want to shoot with a fixed EI setting of 12,800, which is only possible with 3200 and -2 EC. It keeps the flash exposure scaled properly as well. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > >Yes, because it's the only ISO setting not actually based on analog > >gain. > > I dopn't think that's the reason, though, as the 10D's 1600 isn't > hidden, and is pushed 800. When you say pushed you mean via on-camera software, right? I guess it's time for me to read up on exactly how sensors emulate specific ISOs. SignatureMark Photos, Ideas & Opinions http://www.marklauter.com >> >Yes, because it's the only ISO setting not actually based on analog >> >gain. [quoted text clipped - 4 lines] >When you say pushed you mean via on-camera software, right? I guess it's >time for me to read up on exactly how sensors emulate specific ISOs. You're not likely to find any official documentation on this stuff; what is known comes from users reverse-engineering the RAW data. I know this from looking at the RAW data; an ISO 1600 image from a 10D has basically three types of horizontal lines in it; ones that are even all the way across, ones that are odd all the way across, and ones that are alternating between odd and even. This means that the smallest bit in the 12-bit data is totally meaningless, and derived from a 2x multiplication, with a striping thrown over it. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > >> >Yes, because it's the only ISO setting not actually based on analog > >> >gain. [quoted text clipped - 14 lines] > in the 12-bit data is totally meaningless, and derived from a 2x > multiplication, with a striping thrown over it. I tried to understand a previous explanation of this from you but I never got it. Can you explain how you come to those conclusions, step by step? Why is the smallest bit meaningless? Why the 2x multiplication? And what do you mean by striping? Thanks, Greg >> >> >Yes, because it's the only ISO setting not actually based on analog >> >> >gain. [quoted text clipped - 17 lines] >I tried to understand a previous explanation of this from you but I never >got it. Can you explain how you come to those conclusions, step by step? I just did that in the post you replied to. >Why is the smallest bit meaningless? Because it is. How could the smallest bit be meaningful if it is determined by a per-line pattern?: xxxxxxxxxxx1 xxxxxxxxxxx1 xxxxxxxxxxx1 xxxxxxxxxxx1 xxxxxxxxxxx1 or xxxxxxxxxxx0 xxxxxxxxxxx0 xxxxxxxxxxx0 xxxxxxxxxxx0 xxxxxxxxxxx0 or xxxxxxxxxxx0 xxxxxxxxxxx1 xxxxxxxxxxx0 xxxxxxxxxxx1 xxxxxxxxxxx0 Or, if you prefer, from an actual image: http://www.pbase.com/jps_photo/image/38841732/original >Why the 2x multiplication? To hide what they're doing? To standardize the correlation between RAW values and rendered output? I don't know exactly why they do it; I can only speculate. All I can say is that it is done. >And what >do you mean by striping? Lines of odd values, lines of even values, lines of alternating odd and even values. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > >> I know this from looking at the RAW data; an ISO 1600 image from a 10D > >> has basically three types of horizontal lines in it; ones that are even [quoted text clipped - 22 lines] > > xxxxxxxxxxx0 xxxxxxxxxxx1 xxxxxxxxxxx0 xxxxxxxxxxx1 xxxxxxxxxxx0 Ok, since the last bit is the same all the way across the particular line it's meaningless. > Or, if you prefer, from an actual image: > > http://www.pbase.com/jps_photo/image/38841732/original I'll ponder this image again when I have more time but I'm not getting the correlation at the moment. > >Why the 2x multiplication? > [quoted text clipped - 7 lines] > Lines of odd values, lines of even values, lines of alternating odd and > even values. I understand a bit better now. I'm going to try out IRIS one of these days especially since I'm going to do some ultra-beginner astrophotography this weekend with my Rebel XT. Greg > I am wondering why Canon made 3200 a special function. Does that > make sense? Same on the Maxxum 7D, and no it doesn't make sense. I suspect that on the the Maxxum 5D, it will not be special, just another setting. (From the way it's described by Minolta v. the way it was described for the 7D). Cheers, Alan Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. >I am wondering why Canon made 3200 a special function. Does that make >sense? They probably don't want people to use it carelessly, and blame the noise on the camera, so they set it up in such a way as to keep the "____ for dummies" crowd from using it. The 20D's ISO 3200 is really its ISO 1600 under-exposed by a stop, with a stop of highlights thrown away as it doubles the the RAW capture values. Some offer this as the answer to your question, but the 10D did not have ISO 1600 hidden, and its ISO 1600 was the same type of thing (800 pushed to 1600), so that can't be the real explanation. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > They probably don't want people to use it carelessly, and blame the > noise on the camera, so they set it up in such a way as to keep the [quoted text clipped - 5 lines] > not have ISO 1600 hidden, and its ISO 1600 was the same type of thing > (800 pushed to 1600), so that can't be the real explanation. But it is interesting to know that it's not the same as 1600. I guess I could shoot 1600 under exposed and push it myself in either the RAW converter or Photoshop. Film noise wouldn't bother me, but the 3200 noise is jpeggy. SignatureMark Photos, Ideas & Opinions http://www.marklauter.com >But it is interesting to know that it's not the same as 1600. I guess I >could shoot 1600 under exposed and push it myself in either the RAW >converter or Photoshop. Well, you get an extra stop of highlights like that. When the light gets really low, I often just set my 20D to 1600, select the longest shutter speed I feel comfortable with, and Tv mode or manual mode if I'd rather stop the lens down a little. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >When the light gets really low, I often just set my 20D to 1600, select >the longest shutter speed I feel comfortable with, and Tv mode or manual >mode if I'd rather stop the lens down a little. I forgot to mention, this can result in EI values of anywhere from 800 to 400,000 or so. I say 800, because I often set the EC to +1, so that I get a pulled 800 if the lighting is sufficient. Pulling one stop is usually not a problem in low contrast lighting with low contrast scenes. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > >When the light gets really low, I often just set my 20D to 1600, select > >the longest shutter speed I feel comfortable with, and Tv mode or manual [quoted text clipped - 4 lines] > I get a pulled 800 if the lighting is sufficient. Pulling one stop is > usually not a problem in low contrast lighting with low contrast scenes. I'm learning a lot. Thanks. What's an EI value? SignatureMark Photos, Ideas & Opinions http://www.marklauter.com >> >When the light gets really low, I often just set my 20D to 1600, select >> >the longest shutter speed I feel comfortable with, and Tv mode or manual [quoted text clipped - 6 lines] > >I'm learning a lot. Thanks. What's an EI value? That's what you are exposing for, given a hypothetical standard subject, like a grey card. If the camera is set to ISO 3200, and you expose based on a grey card, for 3200, then the EI (Exposure Index) is 3200. If you use +1 EC (Exposure Compensation), then the EI is 1600; if you use -1 EC, the EI is 6400; if you use -4 EC, then the EI is 51,200. You could do this intentionally, or you could do it unintentionally by under-exposing. Of course, for this to be meaningful, you have to render the output display so that a grey card in the scene would look like 18% grey in the output, I should think; IOW, it must be returned to a standard. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > >I'm learning a lot. Thanks. What's an EI value? > > That's what you are exposing for, given a hypothetical standard subject, > like a grey card. > > If the camera is set to ISO 3200, and you expose based on a grey card, <snip> Good explanation. Thanks. Now I have to experiment a little to make sure I got it. SignatureMark Photos, Ideas & Opinions http://www.marklauter.com |
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