AFMA - Is is really necessary?

[Mt Spokane Photography]

Here is an example of a "real world" test case where it's pretty easy to tell, without pixel peeping, whether or not you have a issue with front or back focusing.
-djd

Canon EOS 7D
Focal Length 400mm
Exposure 1/160
F Number f/5.6
ISO 3200

Is it? Its just one image. Things are not quite so simple.

Please consider the following:


The Canon AF system varies from shot to shot, so a thorough test requires that you take several shots setting the lens to infinity or mfd before each shot. Then you need to throw out obvious misfires, and average the others.

That one image that appears to be perfect could, in fact be a misfire, and the other nine be OOF.

2. With a wide aperture lens, the depth of field is very shallow, so its difficult to spot the exact focus on a three dimensional object.

3. You do not "KNOW" exactly where the camera tried to focus, it could have been on the beak, the foot, the tail, or the board the bird is standing on. A properly designed target will insure that the AF system will try to focus on the same spot every time.

 

[Dylan777]

I found AFMA is necessary for big aperture prime lenses: 50L, 85L II etc

My 24-70 II & 70-200 f2.8 IS II are amazing without AFMA.

 

[DJD]

Here is an example of a "real world" test case where it's pretty easy to tell, without pixel peeping, whether or not you have a issue with front or back focusing.
-djd

Canon EOS 7D
Focal Length 400mm
Exposure 1/160
F Number f/5.6
ISO 3200

Is it? Its just one image. Things are not quite so simple.

Please consider the following:


The Canon AF system varies from shot to shot, so a thorough test requires that you take several shots setting the lens to infinity or mfd before each shot. Then you need to throw out obvious misfires, and average the others.

That one image that appears to be perfect could, in fact be a misfire, and the other nine be OOF.

2. With a wide aperture lens, the depth of field is very shallow, so its difficult to spot the exact focus on a three dimensional object.

3. You do not "KNOW" exactly where the camera tried to focus, it could have been on the beak, the foot, the tail, or the board the bird is standing on. A properly designed target will insure that the AF system will try to focus on the same spot every time.

Mt Spokane,
You are absolutely correct. I never intended to imply one photo was enough. It was just to give a real world example for which you should take several to determine if you have a problem or not.

I agree with all the other points you bring up as well which also emphasizes the fact that there are lots of other real world reasons why we don't always get perfect focus where we expect in an image. And they have nothing to do with AFMA.

Cheers,
DJD

 

[Mt Spokane Photography]

Then again, there's the cheap-o DIY version
A 2x8, a step ladder, and any kind of target (in this case, a cardboard box) - see setup.
I take a few photos, manual defocusing before using AF, and estimate the number of inches front or back focusing. Adjust the micro adjust and repeat.

But ... where is the camera actually trying to focus? You can't tell by the red box, because the aF area is larger, and it makes a difference based on exactly where the camera focused. A Camera sensor tends to grab horizontal lines in preference to vertical, and that can have a effect.
There can be lots of gotchas that can lead to wrong conclusions, or they could be right ones, the problem is in knowing which is which.

 

[East Wind Photography]

And some are more sensitive in cross or X pattern. This is good in theory but the target should be better defined and quite a bit larger than the ladder itself to prevent the camera from weighing on it. Otherwise it's just as good or better than Focal.

The latest version 1.8.1 failed on all of my lenses (5-15, 100L 70-200L II, 300 2.8L 600F4L and the latter 3 with and without 1.4XIII and 2XIII extenders) but ironically the older 24-70L. After letting focal do a quick cal as well as a full call on all of my lenses, a check with my spydercal revealed that focal had incorrectly calculated the AFMA on all but the 24-70.

This is quite disappointing as I would have expected an improvement in later versions and instead it has gone the other way. 1.4 seemed to give the best results.

Another interesting thing that happened with 1.8.1 when calibrating my 70-200 2.8L IS II is that on the 200 end at AFMA -20, focal gave it a higher result than at 0. The images were garbage compared to the same with AFMA 0. Even with removing those test points the AFMA calculation was considerably off. Again using the SpyderCal, -3 put the AF dead on 8 out of 8 shots.

To answer the OP question, yes AFMA matters if your lenses are not already dead sharp at 0 AFMA. And you would never know if you dont test them. Software and dot tune are not ideal. Both seem problematic to me and the only sure way to verify everything is to use SPyderCal or LensCal type device, homemade or not.

Then again, there's the cheap-o DIY version
A 2x8, a step ladder, and any kind of target (in this case, a cardboard box) - see setup.
I take a few photos, manual defocusing before using AF, and estimate the number of inches front or back focusing. Adjust the micro adjust and repeat.

But ... where is the camera actually trying to focus? You can't tell by the red box, because the aF area is larger, and it makes a difference based on exactly where the camera focused. A Camera sensor tends to grab horizontal lines in preference to vertical, and that can have a effect.
There can be lots of gotchas that can lead to wrong conclusions, or they could be right ones, the problem is in knowing which is which.

 

[LetTheRightLensIn]

I am semi-pro and use a 5D mark III body and I have recently upgraded my Mk 1 lenses to the 24-70mm f2.8L II and 70-200mm f2.8L II.

I have never bothered with any AFMA and the mark II lenses do look sharp - even in 100% crops, but it has always niggled in my mind that they "could" benefit from some AFMA.

Should I be doing it and, without buying a calibration kit, what is the easiest way to do AFMA?

I have heard a method where you tether the camera to a PC and use the EOS tool to do it - this looks reasonably easy.

yes^yes unless you are really lucky

sometiems just aiming at a crack in the pavement and adjusting works

sometimes just aim at a player and adjust until grass centers around their feet as you like

 

[Rienzphotoz]

ken rockwell says nobody needs AFMA and he knows best.

Looks like CR members have become very polite, coz no one picked up on Malte_P's above post ... usually the mere mention of the name Ken Rockwell instigates much love (or the lack thereof) ;D

 

[NormanBates]

My opinion:

You don't need AFMA if:
* your camera is not reflex (m43 and nex cameras don't have AFMA because they don't need it)
* your lenses don't have AF or you don't plan to use it (don't laugh, that's my personal case)
* you're not going to shoot faster than f/2.8 on APS-C or f/4 on FF

In every other case, AFMA is the one single biggest feature a camera can have. For me, it trumps everything. Even if you're starting out photography, you'll probably grow beyond "I don't need AFMA" in 6 to 12 months. I've seen it before: totally new to photography, buy a 60D with a few lenses, including a 50mm f/1.8 II, six months later sell it and get a second-hand 50D, because of AFMA. Much happier user now.

Some people may just have been lucky with their camera-lens combination. Sending lenses back until you get one that suits your body may be an option for some. For everybody else, lack of AFMA will most probably ruin most fast-aperture pictures.

 

[East Wind Photography]

One of the problems with doing that is that the moire patterns you sometimes get (not sensor moire but from the screen on the camera) on the older models can give you a false interpretation of the results. I have tried very carefully to use the rear screen to eval AF points and then find later after downloading to the PC that it was off. The only thing I can come up with is that the screen DPI even at actual magnification, alters the image slightly enough to make AFMA determination risky (yes I made sure all of the in camera alterations were disabled). 5D3 and 1DX are much better but it's still easier to find the exact AF point on a larger computer screen.

You really need to take the time to evaluate it correctly...sometimes requires going out back and taking 12 shots then coming in to eval, make some tweaks, go back out for another 12 and repeat until you have it nailed down. Anything else and you are simply guessing and unless your AFMA is already way off, it's probably best left at disabled.

I am semi-pro and use a 5D mark III body and I have recently upgraded my Mk 1 lenses to the 24-70mm f2.8L II and 70-200mm f2.8L II.

I have never bothered with any AFMA and the mark II lenses do look sharp - even in 100% crops, but it has always niggled in my mind that they "could" benefit from some AFMA.

Should I be doing it and, without buying a calibration kit, what is the easiest way to do AFMA?

I have heard a method where you tether the camera to a PC and use the EOS tool to do it - this looks reasonably easy.

yes^yes unless you are really lucky

sometiems just aiming at a crack in the pavement and adjusting works

sometimes just aim at a player and adjust until grass centers around their feet as you like

 

[Scott_McPhee]

Well, some great comments here on my original post, thanks for the input and opinions.

I've purchased the Plus version of FoCal and will be giving it a go tonight.
From what I read you can't do fully automatic calibration with the 5D3 but it's as close and you can get.

Anyone know if I add my 1.4 TC to my 70-200 will the camera store separate AFMA data from it than when I use the 70-20 on it's own?

 

[Loswr]

Anyone know if I add my 1.4 TC to my 70-200 will the camera store separate AFMA data from it than when I use the 70-20 on it's own?

Yes, a lens + TC is treated as a unique 'lens' for AFMA value storage.

 

[East Wind Photography]

I think thats only true if it's a canon TC. Will it save say a Canon lens and Kenko TC combo?

Anyone know if I add my 1.4 TC to my 70-200 will the camera store separate AFMA data from it than when I use the 70-20 on it's own?

Yes, a lens + TC is treated as a unique 'lens' for AFMA value storage.

 

[Loswr]

I think thats only true if it's a canon TC. Will it save say a Canon lens and Kenko TC combo?

Depends on the model and firmware (dot color) of the Kenko TC. Some don't report their existence at all, so no separate AFMA. Some that report their existence cause certain Canon camera models (e.g. the 5DIII) to lock up if AMFA is enabled, requiring pulling the battery to reset the camera).

 

[Scott_McPhee]

Mine is a Canon TC so all good.

Hopefully FoCal will take the hassle out of calibrating my lenses - will do all 3 of mine and the 70-200 with the TC.

 

[East Wind Photography]

I hope you find it hassle free. For me it has been more work and disappointment (see my post below). My SpyderCal has been a much better investment in time and $$$.

Mine is a Canon TC so all good.

Hopefully FoCal will take the hassle out of calibrating my lenses - will do all 3 of mine and the 70-200 with the TC.

 

[cayenne]

Well, some great comments here on my original post, thanks for the input and opinions.

I've purchased the Plus version of FoCal and will be giving it a go tonight.
From what I read you can't do fully automatic calibration with the 5D3 but it's as close and you can get.

Anyone know if I add my 1.4 TC to my 70-200 will the camera store separate AFMA data from it than when I use the 70-20 on it's own?

I'm looking and reading about this too....I have a 5D3.

I'm curious, since you have to do the adjustments manually, why did you get the PLUS version rather than the standard version?

I read the FAQ page about 'why they say you should still buy the higher versions', but it didn't make much sense to me what else you get out of the plus vs the standard version really.

Curious your thoughts on the Plus version and why you got it...?

Thanks in advance,

cayenne

 

[Scott_McPhee]

I found the program really easy to use - the only issue for me was it needs a bit of PC POWER to run and it wouldn't run on my little notebook so I had to do all the calibration from my main PC - this was a bit of a pain for me due to the minimum recommended distance for calibrating the far end of my 200mm lens.
I had to use a USB lead extender and place the target on the wall at the far end of my hallway to get the distance.

The calibration results I got were as follows:

50mm F1.4 - +1
24-70mm f2.8L II - W:+1 T:+1
70-200 f2.8L II - W:+4 T+1

Surprised at the 70-200 with the +4 at the wide end but the program was easy to use and I am now shooting with these recommended values. (My 24-70 and 70-200 lenses are brand new.)

I went for the Plus version as (hopefully) 5D3 users will get fully automatic calibration soon, although it's not a real pain now as all you have to do is change the AF Microadjustment (ALL) value when prompted buy the software.

AFMA was always something I avoided doing as the manual method was too hit and miss for me, at least now I can calibrate my lenses on a year to year basis.

Do I notice the differerence after calibration - yes - shots look slightly sharper but I am not sure even a +4 AFMA will produce a very noticable difference on the wide end of my 70-200mmm.

IMO - if you want to calibrate and want to do it easily or have never done it before, FoCal is a good way to go.

 

[comsense]

Do I notice the differerence after calibration - yes - shots look slightly sharper but I am not sure even a +4 AFMA will produce a very noticable difference on the wide end

'Looks' slightly sharper with +\- 1 is definitely a placebo effect. It should not make any difference in non test chart shooting situations and very little even on test charts.

 

[baphomet]

one additional question which has something in parallel with AFMA.
When do you say a picture is 100% sharp., at 100% crop, 300%? What is your expectation?
Background, just got my new 5d mark iii, and also thinking about afma.. at 300% crop I can see that the pictures seem not being sharp, at 100% they do, so now, afma or not ?

 

[Zv]

one additional question which has something in parallel with AFMA.
When do you say a picture is 100% sharp., at 100% crop, 300%? What is your expectation?
Background, just got my new 5d mark iii, and also thinking about afma.. at 300% crop I can see that the pictures seem not being sharp, at 100% they do, so now, afma or not ?

No image will be sharp at 300%. Are you kidding? Look at the image about 50-100%. I prefer 50% when I'm doing PP as it's about as big as it will ever be viewed in real life. 100% for AFMA purposes using Lightrooms compare mode.