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Messages - cccp80

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Finally!

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Sorry it's confusing but the camera model that shows up beneath our names has nothing to do with what we own. I own a 5DII and a micro 4/3 camera. Before that I had an old Rebel (XS).

The standard deviation and the "tolerance range" in number of  AFMA units are not fixed quantities -- variability of the AF will depend on things like subject distance, and available lighting (either ambient or flash/ AF assist). Then the range for which an object appears to be in focus could be 2 or 3 or 5 standard deviations depending on depth of field.

Roger at Lens Rentals had some tests where he looked at the variability of autofocus of some different bodies (including the 5DIII) with some different lenses. My recollection was that with many tested lenses, phase detection on the 5DIII is more consistent than older bodies. Contrast detect (used in live view and on mirrorless bodies) is more accurate but slower. I'd suggest searching lensrentals for the article if you are intersted, it was a good read.

Found the article you were talking about. There are 3 parts and you were right, very good read!

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Hey, elford,
I see you got the 5D mark III.
Is the AF on this model really that much better than on previous models? What is the st. dev for it in Canon's units (if you know of course)?

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I don't think it's really necessary on Rebels since the focusing on them tends to be inconsistent anyway (at least that was the case with my old T2i). AFMA wouldn't fix that.

Not quite. Yes, the phase detection AF on most Canons is inconsistent but you can increase your good image outcome by a lot by doing AFMA. Just to give you an example. Let's say that without any adjustment your average focus is located at +6 with the shot-to-shot error of +/-3 units (that means that the lower and upper bounds are +3 and +9). If you keep it at that you will never get a sharp image. Now, if you do microadjustment of -6 units, you are zeroing your average focus position and your range becomes from -3 to +3 - much better. You will get much better images in this case.

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Should we expect new full frame bodies any time soon?

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EOS Bodies / Re: AFMA – Easy or Not
« on: March 23, 2013, 12:28:09 AM »

I wouldn't say pointless.  I had a zoom that on my 7D needed +3 at the wide end and +7 at the long end.  Leaving it at zero wouldn't be optimal, obviously.  Generally, the DoF will be shallower at the long end.  In that case, +6 was the compromise value.

Having the two settings is nice, though.  The most recent zoom I tested on my 1D X needs 0 at the wide end and +5 at the long end.  But I can imagine that sometimes two settings wouldn't be enough.  The camera does a simple linear regression with focal length between the W and T values. For that lens, the two intermediate focal lengths I tested had AFMA values that fall right on that line.  If they hadn't, the lens would have gone back.

Good point. I like your idea to put the correction closer to the long end. Thanks for the tip!

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EOS Bodies / Re: AFMA – Easy or Not
« on: March 22, 2013, 11:23:16 PM »
Just want to add something that hasn't been discussed before: it is pointless to do microadjust zoom lenses (unless you have the latest models that actually allow to do that) - the amount of correction you will need for smallest/largest focal lengths will be different.

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What I don't understand is why Canon can't release a 36 MP FF sensor???
FF matrix is more than twice the area of the APS-C sensor so even by using the same technology they introduced in 7D over 3 years ago, Canon can start putting out 36 MP full frames.
It seems like now even more than ever Canon needs to step up and show Nikon that we can do it too!

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