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DPChallenge Forums >> Hardware and Software >> Can anyone help ?
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12/04/2007 12:22:06 PM · #1
Just waiting to return my Canon 1D mkIII for the mirror fix but would like to clarify some issues that I feel affect my particular camera.

I use it for covering soccer matches and have found that I have to raise the ISO setting higher than I had to when I used my 20D in comparable conditions.

I tested the two cameras using the same lens (70-200L 2.8)with both set at ISO 200 and aperture 2.8 taking the same subjects and found the 1D mkIII shutter speed was slower than the 20D in every shot which seems to back up my experience at the games.Since the camera was designed for shooting sports, I would have expected the opposite to be the case and for the MKIII to be more sensitive to light.

Can anyone advise?
12/04/2007 12:45:08 PM · #2
Different sensors, likely the sensitivity for a given iso is not truly identical.
12/04/2007 12:49:56 PM · #3
I once read in a review somewhere that the Canon camera's are more sensitive than rated, ie. they are actually at ISO 125 when you select ISO 100. Maybe the mk3 is correctly rated?
12/04/2007 12:55:07 PM · #4
Here's a table of actual ISO sensitivity, it doesn't have Mark III there but it's an indication that not always a ISO200 is the same for all cameras.

dpreview.com

-N.

Message edited by author 2007-12-04 12:55:38.
12/04/2007 04:19:26 PM · #5
Originally posted by nikolaos:

Here's a table of actual ISO sensitivity, it doesn't have Mark III there but it's an indication that not always a ISO200 is the same for all cameras.
-N.

Judging from the table shown..the differences would appear to be between Camera makes rather than models from the same maker.
Which still leaves me puzzled with the results of my test.
I will ask Canon to check this when I get my focus fix.

Thanks to all for the replies
12/04/2007 04:40:16 PM · #6
I don't know if this plays a role in this issue, but here's something to consider...

The sensor on the MKIII is larger than the sensor on the 20D. That being the case, the MKIII sees 'more' of a scene at the same physical focal length than the 20D will. In essence, a 50mm view from a MKIII is a wider angle shot than a 50mm view on a 20D.

If you have your camera's metering system set up in full matrix/evaluative metering, it's completely possible that the camera will meter differently because it's seeing something different over the entire sensor area than the 20D would. If that extra visible area is brighter or darker than what the 20D sees, the MKIII may evaluate the exposure differently based on that. If that's the case, the metering could go either way or remain the same, depending on what the sensor is seeing in that extra area.
12/04/2007 05:29:53 PM · #7
Originally posted by jmsetzler:

I don't know if this plays a role in this issue, but here's something to consider...

The sensor on the MKIII is larger than the sensor on the 20D. That being the case, the MKIII sees 'more' of a scene at the same physical focal length than the 20D will. In essence, a 50mm view from a MKIII is a wider angle shot than a 50mm view on a 20D.

If you have your camera's metering system set up in full matrix/evaluative metering, it's completely possible that the camera will meter differently because it's seeing something different over the entire sensor area than the 20D would. If that extra visible area is brighter or darker than what the 20D sees, the MKIII may evaluate the exposure differently based on that. If that's the case, the metering could go either way or remain the same, depending on what the sensor is seeing in that extra area.


That sounds like a good possibility, I will re-test with that in mind.
Thanks.
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