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Author Topic: AFMA - Is is really necessary?  (Read 7735 times)

comsense

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Re: AFMA - Is is really necessary?
« Reply #15 on: June 19, 2013, 02:15:25 PM »

When a lens requires more than about a 5 point adjustment, the improvement is noticeable, and 10 points or more is flat out obvious.
 

Good point. Example of useful information FoCal (can also DIY but much easier on FoCal) can provide for those who want to know their equipment. What is error range of AF on a given camera? That in turn would decide what AFMA change would bring noticeable difference. However it is important to note that it is hard to measure AF error objectively for cross comparison as it depends on contrast on/near sensors and available light. This is one reason why some advocate using real shooting scenario rather than charts. In simple words, charts would reduce the AF error beyond that is possible in real world shooting, making you obsess for adjustments that wont be relevant in real world.
Now, if you have time and patience, it would not be a bad thing at all to fine tune you equipment even at a test chart level.

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Re: AFMA - Is is really necessary?
« Reply #15 on: June 19, 2013, 02:15:25 PM »

cayenne

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Re: AFMA - Is is really necessary?
« Reply #16 on: June 19, 2013, 02:46:17 PM »
Yes, it matters.  Granted, sometimes a lens-body combo needs no AFMA, but the more lenses you have....

I'd recommend Reikan FoCal.  You've got north of $7K in gear, a small investment in software to get the most from that gear is more than worthwhile, IMO.

I've kinda of been waiting for Magic Lantern's next stable release for the 5D3, and hoping they will have the DotTune auto AFMA parts working....

Would that not do the same as the Focal product?

Cayenne

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Re: AFMA - Is is really necessary?
« Reply #17 on: June 19, 2013, 04:21:22 PM »
I've kinda of been waiting for Magic Lantern's next stable release for the 5D3, and hoping they will have the DotTune auto AFMA parts working....

Would that not do the same as the Focal product?

Perhaps similar to FoCal's new 'quick' method, but it depends on the implementation.  The quick method may not be the same (or as accurate) as the longer method which averages more shots.
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Mt Spokane Photography

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Re: AFMA - Is is really necessary?
« Reply #18 on: June 19, 2013, 04:52:54 PM »
Yes, it matters.  Granted, sometimes a lens-body combo needs no AFMA, but the more lenses you have....

I'd recommend Reikan FoCal.  You've got north of $7K in gear, a small investment in software to get the most from that gear is more than worthwhile, IMO.


I've kinda of been waiting for Magic Lantern's next stable release for the 5D3, and hoping they will have the DotTune auto AFMA parts working....

Would that not do the same as the Focal product?

Cayenne

 
I wonder?  FoCal has been thru a lot in the past year, discovering that the Canon live view AF is not as accurate or reliable as it should be, and having to write their own algorithm to determine accurate focus, for example.
 
As I understand it, dot tune relies on the Canon live view autofocus.  I'm sure its better than nothing, but has already been found to be unreliable.
 
Focal has run so many tests for each body, they have a very good understanding of the system inaccuracies and are still learning and improving.
 
Its interesting to note that the Canon 6D has much more consistent Live AF.
 
http://www.reikan.co.uk/focalweb/index.php/2012/12/af-consistency-comparison-nikon-canon-phase-detect-contrast-detect/

DJD

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Re: AFMA - Is is really necessary?
« Reply #19 on: June 19, 2013, 04:57:23 PM »
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



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Mt Spokane Photography

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Re: AFMA - Is is really necessary?
« Reply #20 on: June 19, 2013, 05:21:26 PM »
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

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Re: AFMA - Is is really necessary?
« Reply #21 on: June 19, 2013, 06:35:32 PM »
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.
Body: 5D III(x2) -- A7r
Zoom: 16-35L II -- 24-70L II -- 70-200L f2.8 IS II
Prime: 40mm -- 50L -- 85L II -- 135L -- 400L f2.8 IS II -- Zeiss FE 55mm f1.8

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Re: AFMA - Is is really necessary?
« Reply #21 on: June 19, 2013, 06:35:32 PM »

Jackson_Bill

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Re: AFMA - Is is really necessary?
« Reply #22 on: June 19, 2013, 08:35:46 PM »
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.


DJD

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Re: AFMA - Is is really necessary?
« Reply #23 on: June 19, 2013, 08:37:21 PM »
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
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Mt Spokane Photography

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Re: AFMA - Is is really necessary?
« Reply #24 on: June 19, 2013, 09:29:56 PM »
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

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Re: AFMA - Is is really necessary?
« Reply #25 on: June 19, 2013, 11:10:19 PM »
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

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Re: AFMA - Is is really necessary?
« Reply #26 on: June 20, 2013, 12:05:08 AM »
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
« Last Edit: June 20, 2013, 12:07:53 AM by LetTheRightLensIn »

Rienzphotoz

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Re: AFMA - Is is really necessary?
« Reply #27 on: June 20, 2013, 01:14:32 AM »
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
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Re: AFMA - Is is really necessary?
« Reply #27 on: June 20, 2013, 01:14:32 AM »

NormanBates

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Re: AFMA - Is is really necessary?
« Reply #28 on: June 20, 2013, 03:25:51 AM »
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.

Jackson_Bill

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Re: AFMA - Is is really necessary?
« Reply #29 on: June 20, 2013, 04:25:59 AM »
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.
I'm focusing (with spot focus) on the flat surface of the box which is in the same plane as the 16" mark (if I recall correctly - its hard to tell from the straight-on photo but easy to see when you're sighting along the surface of the box) on the tape measure. Then I have to estimate where the center of the sharp DOF is.

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Re: AFMA - Is is really necessary?
« Reply #29 on: June 20, 2013, 04:25:59 AM »