December 11, 2017, 02:35:34 PM

Author Topic: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.  (Read 3185 times)

drmikeinpdx

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I received a 5D4 yesterday and as always, my first task was to calibrate it with all of the lenses I might use with it.  Since my collection is pretty large, one might assume that this would be a daunting task.  However, I just happen to know the most amazing method of lens calibration using this one insane trick.  Oh wait, that's for nail fungus.  Here is the real super-easy method:

The first thing you need is a large cardboard mat that is sold in sewing stores for cutting out fabric.  Ignore all the markings except the grid lines.

Lay the mat out flat in bright sunlight or in your studio under your lights and put your camera on your tripod like this:



Stick some black tape on the mat like you see in the photos.  Your autofocus sensors will pick it up perfectly.

If you are calibrating a wide angle lens, you will want to set up your gear closer to the mat than you would if calibrating a longer lens.  I recommend using the same distance at which you would most often use that lens.  You might also consider what lighting conditions you will most often use and try to duplicate that, but I'm probably being obsessive about that.

Get your center focus point somewhere on the black tape and snap an image with enough light to show the grid lines well.  Your aperture should be wide open.

Bring the photo up on your rear LCD screen and hit the magnify button/wheel a few times so that you can easily see the sharp zone. If it isn't centered on the black tape, go into your menu and use the MFA system to change it.  Shoot again and magnify.  Once you get it right, you can quit.  I've not seen any advantage in repeating the process.



The photo above was shot with the EF 85mm F/1.8.  The shallow depth of field makes it very easy to calibrate.  It's also fun to note the chromatic abberration that you get with this lens wide open.




The photo above was shot with the EF 100 F/2.8 L IS macro.  It's a lot sharper lens than the little 85 and you will notice only very slight CA



The final image was taken with the amazing EF 24-70 F/2.8 L II. 

This is a very fast process.  I was able to calibrate 9 lenses in less than an hour and I have complete confidence that they are now properly calibrated with my 5D4 body.  FYI, the calibration settings for this body varied from zero to about +8, so it has a minor tendency to front focus.

You will find that longer lenses are easier to calibrate than wide angle lenses and large aperture lenses are easier than those with small apertures.  Some lenses are almost impossible to calibrate this way, the best example would be the 18-55 kit lenses.  Their poor image quality combined with small max aperture prevents you from seeing a clear zone.

You can also learn interesting things about a lens doing this.  It's easy to get an overall impression of how sharp it is.  I've detected decentered elements and loose zoom assemblies.  (Well, I knew they needed to go to Canon service, and they told me exactly what was wrong.)

On lenses like the EF 50mm F/1.2 L, you can test at different apertures to see if the infamous focus shift is enough for you to worry about.  (It wasn't for me.)

If you happen to have an Art lens, you can test it many times and see how inconsistent the focus is.  You can also do the test with peripheral focus points in addition to the center point to see if you have issues of that sort.  It's a really good way to diagnose possible autofocus problems when you aren't really sure if you have one or not.

I've been using this process for several years and I love it.  One thing I don't like is that when I use a body without MFA capability, I really miss it!

« Last Edit: November 30, 2017, 03:20:16 PM by drmikeinpdx »
Current bodies:  5D4, 5D3, 77D, T5i, S100, S90
Lenses: 24-70 L2, 135 f/2.0 L, Tamron 85 f/1.8, 200 f/2.8 L, 50 f/1.2L, 24-105 L, 70-200 f/4 L, 35 f/2 IS, 24&40 pancakes, EF-S 18-135,
blog:   http://www.BeyondBoudoirPhoto.com

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Dylan777

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Awesome. Thanks for sharing!

Since the day I switched 100% mirrorless, AFMA is no longer on my list  ;)

Click

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Thank you for sharing.   :)

unfocused

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Thanks Dr. Mike,

AFMA is one of those things I know I should do, but just never find the time to do and really didn't want to bother with the elaborate software and setups they seem to require. This seems like a really good and simple method that should be just fine for my purposes.

drmikeinpdx

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If you practice this technique, you quickly learn which lenses are worth calibrating.  Generally, the EF-S kit lenses are not.  The EF 24-105 F/4 L is a nicer kit lens, but the small maximum aperture means it isn't worth the trouble unless you suspect a problem.

I use several large aperture primes, which is where this system really works well.  It's a great way to learn more about your expensive lenses and how they perform.
Current bodies:  5D4, 5D3, 77D, T5i, S100, S90
Lenses: 24-70 L2, 135 f/2.0 L, Tamron 85 f/1.8, 200 f/2.8 L, 50 f/1.2L, 24-105 L, 70-200 f/4 L, 35 f/2 IS, 24&40 pancakes, EF-S 18-135,
blog:   http://www.BeyondBoudoirPhoto.com

AlanF

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This is a variation of a method described by a certain John (geek) at the bottom of the article https://www.the-digital-picture.com/Photography-Tips/af-microadjustment-tips.aspx

The advantage of John's method (which was the first I used before going over to FoCal) is that it is more readily applied to telephotos and indeed wide angle lenses as you can do it on your backyard or a table top.
5D IV, 5DS R, 400mm DO II, 1.4xTC III, 2xTC III, EF 1.8 STM,  EF 24-105, 100-400 II, EF-S 15-85, Sigma 150-600mm C, EOS-M5 15-45, f/2 22, 11-22, Samyang 8mm f/2.8 fisheye: sold 7D II, EOS-M, Powershot G3 X,  Sigma 10-20, EF 300/2.8 II, 70-200/4 IS.

MrFotoFool

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This certainly seems much easier than the test charts. Looks like a good method if you do focus calibration.

I wonder how many people on the forum are like me and have never done it and never found the need to. I currently own three Canon L and one Sigma lens and have owned others over the years. As far as I can tell every one of them focuses fine out of the box. Two of my four would be considered large aperture where it would be more noticeable: 70-200 2.8 and 85 1.4.

I suppose some of you will respond that if I took the time to calibrate I would notice a difference and I suppose you are correct. However it seems like more trouble than it is worth considering I am happy with my current results.

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Mikehit

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I do something similar - put a stake in the lawn and focus at the base of the stake. The  blades of grass round the stake show me how far out the focusing is.
In fact first time I microadjusted was when photographing birds from a hide and I used the accuracy of focus on the bird's eye checking of focus was on the eye or front/far side of the head.

unfocused

  • Canon EF 400mm f/2.8L IS II
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This certainly seems much easier than the test charts. Looks like a good method if you do focus calibration.

I wonder how many people on the forum are like me and have never done it and never found the need to. I currently own three Canon L and one Sigma lens and have owned others over the years. As far as I can tell every one of them focuses fine out of the box. Two of my four would be considered large aperture where it would be more noticeable: 70-200 2.8 and 85 1.4.

I suppose some of you will respond that if I took the time to calibrate I would notice a difference and I suppose you are correct. However it seems like more trouble than it is worth considering I am happy with my current results.

Me too.

I probably should do it, but frankly, there are so many other variables that seem to have a much bigger impact than microfocus that I'm not sure it would do me any good.

Mikehit

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Me too.

I probably should do it, but frankly, there are so many other variables that seem to have a much bigger impact than microfocus that I'm not sure it would do me any good.

The first lens I MA'd was the 100-400mkii on the 7D2 and it certainly helped - and I did it because I had identified a lot of missed focus. I MA'd the 400 DOii on the 1Dx2 just because I could and it was a slight adjustment but I was never happy with it so reset to zero. If you are gong to do it I think the key thing is to take several shots to make sure it was not simply 'a variable'.

Mt Spokane Photography

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The horizontal lines are the key, the camera prerfers to focus on a horizontal line.  It may pick anywhere to focus unless you provide a nice horizontal line.

There are other considerations like color of the light that affect AF, so, the focus method is somewhat limited to the color of lighting used.

The folks at FoCal have done a lot of testing and have come up with a list of things which affect AF accuracy, so its not as simple as we'd like to believe.  I do think the method you show is accurate enough for almost everyone.

scottkinfw

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Thanks Dr. Mike,

AFMA is one of those things I know I should do, but just never find the time to do and really didn't want to bother with the elaborate software and setups they seem to require. This seems like a really good and simple method that should be just fine for my purposes.

Unfocused, you really really really need to calibrate before your next shoot- chances are, your pics are softer than they need to be.

Scott
Cameras: 1DXII,5D III, 5D II.  Lenses    24-70 2.8L II IS, 70-200 f4L IS, 70-200 f2.8L IS II, EF 400 5.6L, 300 2.8 IS II, Samyang 14 mm 2.8.   Flashes: 600EX-RT X 2, ST-E3-RT, 580 EX II.
Plus lots of stuff that just didn't work for me

scottkinfw

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The horizontal lines are the key, the camera prerfers to focus on a horizontal line.  It may pick anywhere to focus unless you provide a nice horizontal line.

There are other considerations like color of the light that affect AF, so, the focus method is somewhat limited to the color of lighting used.

The folks at FoCal have done a lot of testing and have come up with a list of things which affect AF accuracy, so its not as simple as we'd like to believe.  I do think the method you show is accurate enough for almost everyone.

I am finding that Focal is messing up my 1DXII.  I'm putting in a ticket with them.

Anybody else with L lenses and a 1DXII have issues with 1DXII

Scott
Cameras: 1DXII,5D III, 5D II.  Lenses    24-70 2.8L II IS, 70-200 f4L IS, 70-200 f2.8L IS II, EF 400 5.6L, 300 2.8 IS II, Samyang 14 mm 2.8.   Flashes: 600EX-RT X 2, ST-E3-RT, 580 EX II.
Plus lots of stuff that just didn't work for me

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Ian_of_glos

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The horizontal lines are the key, the camera prerfers to focus on a horizontal line.  It may pick anywhere to focus unless you provide a nice horizontal line.

There are other considerations like color of the light that affect AF, so, the focus method is somewhat limited to the color of lighting used.

The folks at FoCal have done a lot of testing and have come up with a list of things which affect AF accuracy, so its not as simple as we'd like to believe.  I do think the method you show is accurate enough for almost everyone.

I am finding that Focal is messing up my 1DXII.  I'm putting in a ticket with them.

Anybody else with L lenses and a 1DXII have issues with 1DXII

Scott
When I used Focal with my 5D mark 3 and an assortment of lenses I found the results were very inconsistent. The recommended adjustment was different every time. Focal said that it was because I did not have enough light on my target, but I don't have this problem with other, simpler methods such as Dot Tune.

Jean

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Since i have a DPAF camera (70D & 6Dmk ii) i adjust focus by comparing the difference of focus  movement of the lens in live view vs. OVF movement. In live view i magnify ten times to check the focus on the target. When the lens doesn't move after switching and refocussing between live view and OVF i think the value stored is the right one.
Useually i use approx. 50 times focal distance.
Anybody with same sort of experiences?
Carpe Diem

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