1d Mark III poor low light AF

Started Feb 13, 2008 | Discussions thread
child of enki New Member • Posts: 4
Re: five

Mako2011 wrote:

The thread is 5 years old. I wonder if it's still an issue for the OP

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My opinions are my own and not those of DPR or its administration. They carry no 'special' value (except to me and Lacie of course)

Probably not. Chance's are he sold the camera to some poor schmuck and switched to Nikon like so many did back then.

It's time to take you all to school.

One of the beautiful things about being an engineer is that unlike most you stuck up photographers I actually know how to analyze a cameras behavior and determine the problem.

After a series of on and off axis light tests I have determine that the 1D Mark III & even IV suffer from diminished AF performance for two reasons. The first one has something to do with the sensitivity of the pickup sensor. The cameras focus accuracy actually is thrown off more in low light. If you photograph a  static object with adequate lighting  the camera will constantly lock focus on that object accurately every time. However if you shift the axes of the light your lens (REGARDLESS OF MODEL) will start to misfocus. Naturally, if you use a faster lens it will buy you more low light accuracy however the issue is still there which is why (at least for some) the 5D and just about every other Camera acquire focus faster and more accurately in low light. the bottom line is this. Neither the 1D MK III or MK IV that I'm testing are able to focus down to -1ev as advertised. Furthermore, because of so many of you peoples constant arrogance to what many have been saying, this issue has never been addressed by Canon & even found its way into the MK IV.

Now for the second problem. This problem only effects the MK III. Prolonged usage in low light also effects the camera's ability to lock focus. This however won't really matter since your focus accuracy disappears the more the camera struggles in low light so you probably will not even use it.

The good news is that there is a solution for both problems.  Use some form of AF assist and you should be okay. the camera will not respond as quickly as it would if it were working properly and you likely won't want to use it to track anything in low light but at least you will be able to use it in dim light like outdoors at night.

Anyway, that's what's wrong.

For the record, the MK III tested was manufactured outside of the range of cameras that had to be recalled for the mirror assembly fix. Serial number is 550XXX

Other cameras tested were the 1D, 1D MK II, 40D and 5D MK II. All were able to accurately lock focus better than both the 1D MK III  and 1D MK IV in low light conditions.

And by the way this issue was brought up once by Rob Galbraith in a series of over 20 articles called "An analysis of EOS-1D Mark III autofocus performance". In one of the articles it was claimed that firmware v1.2.3 and v1.1.2 fixed this issue for both the 1D MK III and 1Ds MK III however the MK III  I'm working with is on Firmware Ver 1.3.0 and they never when into any detail as to how they tested the so called fix.


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