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Technique and Advice => Photography Technique => Topic started by: drmikeinpdx on November 30, 2017, 03:12:40 PM

Title: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: drmikeinpdx on November 30, 2017, 03:12:40 PM
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:

(http://www.beyondboudoirphoto.com/img/s1/v47/p2652108476-5.jpg)

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.

(http://www.beyondboudoirphoto.com/img/s4/v65/p2652108468.jpg)

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.


(http://www.beyondboudoirphoto.com/img/s1/v49/p2652108470-5.jpg)

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

(http://www.beyondboudoirphoto.com/img/s7/v164/p2652108528-5.jpg)

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!

Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: Dylan777 on November 30, 2017, 03:24:14 PM
Awesome. Thanks for sharing!

Since the day I switched 100% mirrorless, AFMA is no longer on my list  ;)
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: Click on November 30, 2017, 06:58:15 PM
Thank you for sharing.   :)
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: unfocused on November 30, 2017, 08:29:07 PM
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.
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: drmikeinpdx on December 01, 2017, 12:55:50 AM
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.
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: AlanF on December 01, 2017, 03:29:58 AM
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.
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: MrFotoFool on December 06, 2017, 04:50:17 PM
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.
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: Mikehit on December 06, 2017, 05:33:54 PM
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.
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: unfocused on December 06, 2017, 06:00:31 PM
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.
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: Mikehit on December 06, 2017, 06:35:40 PM

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'.
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: Mt Spokane Photography on December 06, 2017, 09:17:39 PM
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.
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: scottkinfw on December 06, 2017, 09:38:00 PM
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
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: scottkinfw on December 06, 2017, 09:41:50 PM
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
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: Ian_of_glos on December 07, 2017, 03:02:29 AM
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.
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: Jean on December 07, 2017, 08:09:00 AM
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?
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: Luds34 on December 07, 2017, 08:47:21 AM
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?

Yes, I do something similar. I just shoot a test chart and compare between liveview and PDAF. I usually try to defocus near and far, just to make sure there is no discrepancy depending on where the focus started from.

BTW, while I did do this with my old 70D and new 6D2, this method worked fine with my old 6D. DPAF is just so much faster, the old contrast detection, while very slow, is just as accurate. In fact I'm quite sure all the mirrorless cameras fine tune to "accurate focus" with contract detection after letting the phase detection get it most of the way there.
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: picturefan on December 07, 2017, 11:46:19 AM
I'm used to some EOS Cameras, which the 7D MKII is the latest of them.
4 (!) L-Lenses and some no-canon-lenses do not focus correctly, means I need to do some "time consuming" afma with them.
The only high aperture lens delivering tack sharp images with the 7d MkII-af is the nifty-fifty, stm-version.
Not really satisfying for such a pricey equipment...
DPAF is working well, but not fast enough for some wildlife.
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: Sporgon on December 07, 2017, 03:26:14 PM
This thread caught my eye because I have found that checking focus on a sloping target is unreliable.

I have my own quick method: usual things, good light, solid tripod etc. I have a well defined vertical target and ensure the camera is lined up horizontally on the centre point. Using BBF I take a shot using TTL phase AF. I then switch to live view and x10. Gently moving the focusing ring I see if I can improve on the sharpness, noting which way I'm turning the focusing ring, rear or far. I do this four times. If there is a consistent difference I then adjust the AFMA by the amount I guess it's out, if any, normally starting at +\ - 5. Then repeat four times. Assess.  Hone in from there.

Maybe I'm lucky, but all my lenses are naf all out.

This method isn't as easy to do on a STM lens or an original 5D.
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: Talys on December 07, 2017, 03:54:15 PM
Neat stuff, thanks for sharing :D

I think you'd have some problems with this method using telephoto lens, just getting enough distance to the target.

A long time ago, I used a cheap cardboard foldout from Amazon that cost something like $5.  It worked fine; I still have it mounted to tripod-friendly plate.  Then, I bought a fancier LensCal, which worked a little better.  Dot Tune is totally free, but it has not worked as consistently for me.

The problem with all of these methods is if you have more than a couple of lenses.  I think I have something like 8 zoom and 5 prime lenses (at least, that I care about AFMA with)... it takes FOREVER to AFMA them all manually.  I can blow a whole day, and still second guess myself.  It also sucks if I buy a new zoom lens, because with 4 bodies, it means that I have to do 8 calibrations.  Or, at least 4 calibrations, for my 2 favorite bodies.

If your camera supports Reikan FoCal in full auto mode, I highly recommend it.  Sometimes I may disagree with it slightly, but overall, it saves me so much time.  If I'm suspicious of the result, I will use a LensCal and double-check it, but pretty much always, I'm the one that is wrong :) 
Title: Re: My favorite method of focus calibration. Cheap, fast, accurate and foolproof.
Post by: CanonFanBoy on December 11, 2017, 06:54:56 AM
Thanks! Great idea!