September 16, 2014, 05:27:46 AM

Author Topic: Strange AFMA results with canon 50 f1.4  (Read 2600 times)

lastcoyote

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Strange AFMA results with canon 50 f1.4
« on: February 22, 2014, 06:18:43 PM »
Ok this ones strange.
Just been adjusting the AFMA for my canon 50 f1.4 on my 5D III.
I've found that I have to set it to around +15 when aperture is wider than f4 and particularly when shooting at medium to far distances. But if aperture is f4 or narrower and particularly when subject is at close distances it's best left at around +5.

Anyone experienced similar?

All my other lenses AFMA settings are unaffected by aperture changes.
« Last Edit: February 24, 2014, 03:11:50 PM by lastcoyote »
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Strange AFMA results with canon 50 f1.4
« on: February 22, 2014, 06:18:43 PM »

lastcoyote

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Re: Strange AFMA results with canon 50 f1.4
« Reply #1 on: February 23, 2014, 07:57:07 AM »
Having searched for this problem now it appears that this is common with this lens design. It suffers from focus shift with aperture changes.  :( what a pain.

So I've kind of settled on leaving it set to +10 as this seems fairly accurate at most distances and apertures that will be common to my shooting needs/style.
« Last Edit: February 24, 2014, 03:12:49 PM by lastcoyote »
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alexturton

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Re: Strange AFMA results with canon 50 f1.4
« Reply #2 on: February 25, 2014, 07:59:41 AM »
yes agreed. its called focus shift.

Something to do with the lack of an extra spherical lens to keep the bokeh smooth, means that aberations are uncorrected. That results in the focus shifting when stopped down.

I could calibrate at f1.4; thats what I used to do with my 1.4.

Interestingly the 50L 1.2 is supposed to be afflicted with the same problem. However I bought one a month ago and it demonstrates no focus shift. so perhaps there is also a little sample variation which worsens the focus shift effect...?



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mackguyver

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Re: Strange AFMA results with canon 50 f1.4
« Reply #3 on: February 25, 2014, 09:14:35 AM »
yes agreed. its called focus shift.

Something to do with the lack of an extra spherical lens to keep the bokeh smooth, means that aberations are uncorrected. That results in the focus shifting when stopped down.

I could calibrate at f1.4; thats what I used to do with my 1.4.

Interestingly the 50L 1.2 is supposed to be afflicted with the same problem. However I bought one a month ago and it demonstrates no focus shift. so perhaps there is also a little sample variation which worsens the focus shift effect...?
Alex, the newer 50 1.2s don't seems to suffer from this as much but you'll see some focus shift as you get close to the minimum focus distance.  It's not terrible, because you can easily adjust focus manually when you are that close to something - and with a 50mm, it's rare you would actually want to be shooting something 1.5-2 feet away.

As for the 50 1.4, I don't remember that being an issue, but I shot just about everything at f/2 when I owned that lens, which seemed to be the sweet spot in terms of sharpness/contrast/DOF.
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borneosailor

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Re: Strange AFMA results with canon 50 f1.4
« Reply #4 on: February 25, 2014, 09:46:41 AM »
ok I know this sounds silly or off topic (please excuse me), does the "exotic" 50mm f1.0 suffer from focus shift too?
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wickidwombat

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Re: Strange AFMA results with canon 50 f1.4
« Reply #5 on: February 25, 2014, 10:05:52 AM »
honestly try this lens with no AFMA it will perform far better than atempting to AFMA it
if its off considerably i would send it in to be adjusted by canon to be closer to neutral
or if not in warranty sell it and get something else
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Re: Strange AFMA results with canon 50 f1.4
« Reply #6 on: February 25, 2014, 11:42:06 AM »
Im on -13 with my 35/1.4 and on +6 with my 50/1.4 .. The only canon lens i've owned in the past years that was spot on from the start was the 40/2.8. I cant use the 35 wide-open on my EOS3 for example becasue its that much off :/

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Re: Strange AFMA results with canon 50 f1.4
« Reply #6 on: February 25, 2014, 11:42:06 AM »

Old Shooter

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Re: Strange AFMA results with canon 50 f1.4
« Reply #7 on: February 25, 2014, 03:00:01 PM »
Im on -13 with my 35/1.4 and on +6 with my 50/1.4 .. The only canon lens i've owned in the past years that was spot on from the start was the 40/2.8. I cant use the 35 wide-open on my EOS3 for example becasue its that much off :/

That is so funny! Same for me too! I've got some pretty expensive glass and only my $150 shorty-forty requires no AFMA!
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Aglet

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Re: Strange AFMA results with canon 50 f1.4
« Reply #8 on: February 25, 2014, 03:16:46 PM »
I kept my old, NIB 50/1.4 and sold my battle-worn but reliable old one.
Silly me to do that without first testing the one in the box!

The new one has some strange behavior where it focuses perfectly, but only at certain distances, everywhere else it's either front or back focusing by as much as 2 feet at a 12 foot distance, for example.
This was tested using only center AF point on 3 different crop bodies, all with the same results and repeatable.
The old one nailed focus reliably, even if it did show a wee bit of focus shift when stopping down.
This newer lens is not even in the general vicinity most of the time.
Very disappointing and since it's well past warranty, I'm either fixing it myself or selling it.  I need it to AF, MF not an option for my intended use.

Anyone else have a 50/1.4 USM behave like that and what was the specific fix?
Perhaps it's a position encoder on the drive train that's not working properly?

Edit - fixed many typos.
« Last Edit: February 26, 2014, 02:11:50 AM by Aglet »

robbinzo

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Re: Strange AFMA results with canon 50 f1.4
« Reply #9 on: February 25, 2014, 05:21:51 PM »
AFMA for my 50 f/1.4 seems to change every time I put it on my 70D.
Using Reikan Focal I get somewhere from +13 to +20 at f/1.4.
My lens also varies with subject distance.
I have sent this lens back to Canon and it came back exactly the same.
I've posted before that I use live view on my 70D with this lens whenever possible because it's so hit and miss through the viewfinder. The dual pixel liveview AF has been much more accurate for me with this lens.
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horshack

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Re: Strange AFMA results with canon 50 f1.4
« Reply #10 on: February 25, 2014, 11:49:09 PM »
The 50 is one of my favorite Canon lenses but it's micro-USM motor makes it a rather finicky and imprecise focusing lens (shot-to-shot variability). I've had the most success with it by tuning at infinity - that produces good results at all distances whereas the opposite is not true (tuning at 50x and expecting it to focus well at middle to infinity distances).

LetTheRightLensIn

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Re: Strange AFMA results with canon 50 f1.4
« Reply #11 on: February 26, 2014, 03:14:09 PM »
Having searched for this problem now it appears that this is common with this lens design. It suffers from focus shift with aperture changes.  :( what a pain.

So I've kind of settled on leaving it set to +10 as this seems fairly accurate at most distances and apertures that will be common to my shooting needs/style.

EVen worse, the stepping motor is not refined at all and it often slightly over or under shoots and it can't be adjusted precisely enough for f/1.4 shooting either and it tends to break and so on. Terrible AF mechanism in this lens. Optically it's just fine for a regular Double Gauss design though (although obviously pales by miles compared to an advanced and expensive Otus type design).

LetTheRightLensIn

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Re: Strange AFMA results with canon 50 f1.4
« Reply #12 on: February 26, 2014, 03:16:58 PM »
I kept my old, NIB 50/1.4 and sold my battle-worn but reliable old one.
Silly me to do that without first testing the one in the box!

The new one has some strange behavior where it focuses perfectly, but only at certain distances, everywhere else it's either front or back focusing by as much as 2 feet at a 12 foot distance, for example.
This was tested using only center AF point on 3 different crop bodies, all with the same results and repeatable.
The old one nailed focus reliably, even if it did show a wee bit of focus shift when stopping down.
This newer lens is not even in the general vicinity most of the time.
Very disappointing and since it's well past warranty, I'm either fixing it myself or selling it.  I need it to AF, MF not an option for my intended use.

Anyone else have a 50/1.4 USM behave like that and what was the specific fix?
Perhaps it's a position encoder on the drive train that's not working properly?

Edit - fixed many typos.

yes, that is very common for this lens

you can try to have Canon adjust it, but the internal adjustments on it are weak

for some reason the 5D3 seems to make it focus more reliably than other bodies such as xxD or 7D or 5D2 (to a greater extent than the difference with other lenses)

the real fix may be when Canon finally releases and update with a properly designed AF or maybe the new Sigma that is coming out soon


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Re: Strange AFMA results with canon 50 f1.4
« Reply #12 on: February 26, 2014, 03:16:58 PM »

nicku

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Re: Strange AFMA results with canon 50 f1.4
« Reply #13 on: February 27, 2014, 06:05:59 AM »
Ok this ones strange.
Just been adjusting the AFMA for my canon 50 f1.4 on my 5D III.
I've found that I have to set it to around +15 when aperture is wider than f4 and particularly when shooting at medium to far distances. But if aperture is f4 or narrower and particularly when subject is at close distances it's best left at around +5.

Anyone experienced similar?

All my other lenses AFMA settings are unaffected by aperture changes.

When i get my first Canon 50mm f/1.4 , was very difficult to micro adjust the lens...

The remedy:
return it back and get a Sigma 50mm f/1.4, way, way over the Canon lens in all aspects.  ;)

ftico

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Re: Strange AFMA results with canon 50 f1.4
« Reply #14 on: February 27, 2014, 04:18:38 PM »
Got two 50 1.4 and tested them in order to keep the best w respect to focus shift. However, they behaved pretty much the same on my 70D. Interestingly, perceived accuracy from results w standard AF were better than results w precise manual focus or dual pixel AF.

I ended up keeping the one w better clarity, and AFMA for most used aperture/distance.
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Re: Strange AFMA results with canon 50 f1.4
« Reply #14 on: February 27, 2014, 04:18:38 PM »