July 31, 2015, 01:13:51 AM

Author Topic: AFMA values beyond -20  (Read 1231 times)

Gert Arijs

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AFMA values beyond -20
« on: March 07, 2014, 10:04:10 AM »
Hi,
I have bought a used 5D3 last month and recently the Tamron 24-70 f/2,8 VC (also used). I just did AFMA for this lens (as I did with my other lenses before) and even with the value set to -20, it's just not enough. It should be about -22 for Wide and about -26 for Tele (these are educated guesses). What can I do?
Notes:
-I performed a more or less "real life" test at f/4 and it's perfectly ok. Same test at f/2,8 and it seems quite ok.
-I do the following to determine the AFMA values: Tripod, detailed flat object (ie newspaper), camera and object aligned. I defocus manually, and autofocus; then I check the focus using liveview and adjust manually when necessary; I repeat this about 3 times using the middle focus point first and another 3 times for two outer focus points (both left and right). I always defocus first.
-I got very consistent results with my other lenses on this and previous bodies. So I'm confident I do not need FoCal or other packages. It's just this Tamron, which seems too off for calibration but turns out to be ok in real life...
Suggestions?
« Last Edit: March 07, 2014, 10:09:07 AM by Gert Arijs »
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AFMA values beyond -20
« on: March 07, 2014, 10:04:10 AM »

neuroanatomist

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Re: AFMA values beyond -20
« Reply #1 on: March 07, 2014, 10:09:29 AM »
All you can really do is send the lens, body, or both into their respective manufacturers for adjustment.
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wickidwombat

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Re: AFMA values beyond -20
« Reply #2 on: March 09, 2014, 01:16:30 AM »
yep send it in for recalibration then it should come back good
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Gert Arijs

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Re: AFMA values beyond -20
« Reply #3 on: May 27, 2015, 02:31:29 PM »
After intensive use, I found it has "focus shift" problems. F/2.8-4 is fine, but 5.6 and beyond is not in focus. That was problematic with group shots. I could work around it, but it's still a pain in the thing. AFMA-values seemed to be less extreme then first found since I bought Reikan Focal.
The internet learned me that it occured with te older 24-70 VC's. I hope it can be fixed.

I just sent my lens in last weekend. It will be back after 4-6 weeks. That's way too long for me, it's a zoom I can't live without. So I decided to buy the Canon 24-70 f/2.8 II. I'm guessing it will be my new favorite lens...
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Mt Spokane Photography

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Re: AFMA values beyond -20
« Reply #4 on: May 27, 2015, 10:00:08 PM »
After intensive use, I found it has "focus shift" problems. F/2.8-4 is fine, but 5.6 and beyond is not in focus. That was problematic with group shots. I could work around it, but it's still a pain in the thing. AFMA-values seemed to be less extreme then first found since I bought Reikan Focal.
The internet learned me that it occured with te older 24-70 VC's. I hope it can be fixed.

I just sent my lens in last weekend. It will be back after 4-6 weeks. That's way too long for me, it's a zoom I can't live without. So I decided to buy the Canon 24-70 f/2.8 II. I'm guessing it will be my new favorite lens...
Focus shift is actually caused by chromatic and spherical aberration.  It does affect that lens, there is no adjustments possible, since its built in to the lens design.


It should be a minor effect at f/5.6, but starts to be noticible at f/11.

You can adjust AFMA to focus to the rear a very slight amount, which will take care of it.

Your note of a AFMA of over 20 means there is likely a lens issue.  I always subtract the average cost of a repair from the price of a lens, because owners are selling for a reason.  They may not like the images but don't recognize the lens has a problem. 


Marsu42

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Re: AFMA values beyond -20
« Reply #5 on: May 28, 2015, 07:01:16 AM »
All you can really do is send the lens, body, or both into their respective manufacturers for adjustment.

... the other possibility is to simply use Magic Lantern which lets you enter afma values that exceed Canon's bounds (up to +-100, if I remember correctly).

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Re: AFMA values beyond -20
« Reply #5 on: May 28, 2015, 07:01:16 AM »