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Author Topic: Canon 24-70 f/2.8L mkii Focus Shift  (Read 3676 times)

teedidy

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Canon 24-70 f/2.8L mkii Focus Shift
« on: March 22, 2013, 12:22:35 PM »
HI All,

I have just received my (2nd copy) Canon 24-70 f/2.8 mk II. Being a faithful CR follower and reading http://www.canonrumors.com/tech-articles/how-to-test-a-lens/ I begain from the top and followed ever step I could as best as I could. I also have Reikan Focal and ran through every testing option there was available. What I have found suprised me to the point I originally thought I had received the dreaded bad copy.

There is a definite focus shift on the 24-70 mk II. I have found that from f4 to f5.6 it starts to back focus severely  -5 afma vs +3 afma for f2.8 to f4 and +3 afma f5.8 on.

I am surprised there is not more information already out there on this.
I Found this on a competing forum  http://www.fredmiranda.com/forum/topic/1177402 very similar findings

I understand through research you can hold the DOF button down to get around this issue? But would that reduce effectiveness of the f2.8 cross focus points?

After a quick search it appears the Tamron 24-70 has a very similar focus shift issue. 
http://www.lenstip.com/340.5-Lens_review-Tamron_SP_24-70_mm_f_2.8_Di_VC_USD_Chromatic_and_spherical_aberration.html

Does anyone have any advice? At this point I don't know what to do?

Thank you for your time.
5DmkIII, 24-70 f/2.8L, 50 f/1.4, 70-200 f/2.8L, 430ex(I and II) 580ex I, 50D(backup and ML Video)

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Canon 24-70 f/2.8L mkii Focus Shift
« on: March 22, 2013, 12:22:35 PM »

teedidy

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Re: Canon 24-70 f/2.8L mkii Focus Shift
« Reply #1 on: March 22, 2013, 01:07:35 PM »
I forgot to mention, This only happens at the long end, 70mm. At 24mm there is no issue at all.
5DmkIII, 24-70 f/2.8L, 50 f/1.4, 70-200 f/2.8L, 430ex(I and II) 580ex I, 50D(backup and ML Video)

LetTheRightLensIn

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Re: Canon 24-70 f/2.8L mkii Focus Shift
« Reply #2 on: March 22, 2013, 01:39:59 PM »
Did you find it only for close shooting distance or in general?
I found it happens to a considerable degree when shooting near MFD. I haven't looked into it much when shooting at greater distances. I suspect it is OK there.

teedidy

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Re: Canon 24-70 f/2.8L mkii Focus Shift
« Reply #3 on: March 22, 2013, 02:02:48 PM »
Did you find it only for close shooting distance or in general?
I found it happens to a considerable degree when shooting near MFD. I haven't looked into it much when shooting at greater distances. I suspect it is OK there.


Good point. When I am near MFD  at 5 feet away at f4 the Total Depth of Field is only 1.5 inches ( http://www.cambridgeincolour.com/tutorials/dof-calculator.htm )(Assume 20/20 vision on a 10in print )
This is where I see it, because at twice that distance the total depth of field is 6.2 inchs.

5DmkIII, 24-70 f/2.8L, 50 f/1.4, 70-200 f/2.8L, 430ex(I and II) 580ex I, 50D(backup and ML Video)

jonathan7007

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Re: Canon 24-70 f/2.8L mkii Focus Shift
« Reply #4 on: March 22, 2013, 03:54:19 PM »
I believe my copy of this lens does the same thing, but I am trying to redo my Reikan test (which produced + numbers -- opposite of expected result) and get time and conditions for a better test. Back focus observed in real-world exposures in which I would not expect last-second movement. But perhaps the same as your lens...

teedidy

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Re: Canon 24-70 f/2.8L mkii Focus Shift
« Reply #5 on: March 22, 2013, 04:13:25 PM »
I believe my copy of this lens does the same thing, but I am trying to redo my Reikan test (which produced + numbers -- opposite of expected result) and get time and conditions for a better test. Back focus observed in real-world exposures in which I would not expect last-second movement. But perhaps the same as your lens...

This is my second copy of this lens since I thought the first was a bad copy. I guess if I decide I am going to keep this lens, I need to fully understand what it can and cannot do. I also need to fully understand what I can do to overcome its short comings. I tend to shoot mostly photos around my house with little sticky fingers reaching for the camera. Therefore I tend to shoot a large number of shots inside 3 feet. As long as I keep it at f/2.8 I have no issues, but that will not always be possible.
5DmkIII, 24-70 f/2.8L, 50 f/1.4, 70-200 f/2.8L, 430ex(I and II) 580ex I, 50D(backup and ML Video)

Viggo

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Re: Canon 24-70 f/2.8L mkii Focus Shift
« Reply #6 on: March 22, 2013, 04:32:11 PM »
Is this normal or is it just the new 24-70?

I've never noticed any shift from other than my 50 L and we all know that has some shift. I also never noticed any shift with any of my 70-200's and I use all lenses up close for 85% of my shots ..
1dx, 17-40 L, 24-70 L II, 85 L II, 200 f2.0 L

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Re: Canon 24-70 f/2.8L mkii Focus Shift
« Reply #6 on: March 22, 2013, 04:32:11 PM »

teedidy

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Re: Canon 24-70 f/2.8L mkii Focus Shift
« Reply #7 on: March 22, 2013, 05:03:56 PM »
Is this normal or is it just the new 24-70?

I've never noticed any shift from other than my 50 L and we all know that has some shift. I also never noticed any shift with any of my 70-200's and I use all lenses up close for 85% of my shots ..

In my testing it is only in the longer end 70mm was the worst, 50mm not as bad but still noticeable. Zero focus shifting at 24mm. I Tested out the 24-105. I was unable to find any focus shift at 70mm.
5DmkIII, 24-70 f/2.8L, 50 f/1.4, 70-200 f/2.8L, 430ex(I and II) 580ex I, 50D(backup and ML Video)

Viggo

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Re: Canon 24-70 f/2.8L mkii Focus Shift
« Reply #8 on: March 23, 2013, 06:57:34 AM »
Is this normal or is it just the new 24-70?

I've never noticed any shift from other than my 50 L and we all know that has some shift. I also never noticed any shift with any of my 70-200's and I use all lenses up close for 85% of my shots ..

In my testing it is only in the longer end 70mm was the worst, 50mm not as bad but still noticeable. Zero focus shifting at 24mm. I Tested out the 24-105. I was unable to find any focus shift at 70mm.

Thanks! I just bought myself a mint used 24-70 mk1 for almost zero
Money so I'll leave the mk 2 for a while..
1dx, 17-40 L, 24-70 L II, 85 L II, 200 f2.0 L

Dylan777

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Re: Canon 24-70 f/2.8L mkii Focus Shift
« Reply #9 on: March 25, 2013, 09:51:20 AM »
I ran my copy through FoCal again, yesterday. Nothing happen on my copy 24, 35, 50, and 70mm(f2.8 to f8). My copy was from very 1st patch ;D
« Last Edit: March 25, 2013, 09:56:18 AM by Dylan777 »
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

Mt Spokane Photography

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Re: Canon 24-70 f/2.8L mkii Focus Shift
« Reply #10 on: March 25, 2013, 11:08:37 AM »
HI All,

I have just received my (2nd copy) Canon 24-70 f/2.8 mk II. Being a faithful CR follower and reading http://www.canonrumors.com/tech-articles/how-to-test-a-lens/ I begain from the top and followed ever step I could as best as I could. I also have Reikan Focal and ran through every testing option there was available. What I have found suprised me to the point I originally thought I had received the dreaded bad copy.

There is a definite focus shift on the 24-70 mk II. I have found that from f4 to f5.6 it starts to back focus severely  -5 afma vs +3 afma for f2.8 to f4 and +3 afma f5.8 on.

I am surprised there is not more information already out there on this.
I Found this on a competing forum  http://www.fredmiranda.com/forum/topic/1177402 very similar findings

I understand through research you can hold the DOF button down to get around this issue? But would that reduce effectiveness of the f2.8 cross focus points?

After a quick search it appears the Tamron 24-70 has a very similar focus shift issue. 
http://www.lenstip.com/340.5-Lens_review-Tamron_SP_24-70_mm_f_2.8_Di_VC_USD_Chromatic_and_spherical_aberration.html

Does anyone have any advice? At this point I don't know what to do?

Thank you for your time.

 
Either exchange it again, or send the lens to Canon for adjustment.  I'd say exchange it if you can.  It might have a issue at 70mm.
 
Due to residual spherical aberration,  a lens focus will appear to shift towards the rear, but the 24-70 should do it only very slightly.  For the most part, its just the depth of field that increases more towards the rear as you stop down.
You can decrease the aperture on this photozone chart and see it.
http://www.photozone.de/canon_eos_ff/773-canon2470f28mk2ff?start=1
 
http://toothwalker.org/optics/spherical.html

teedidy

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Re: Canon 24-70 f/2.8L mkii Focus Shift
« Reply #11 on: March 31, 2013, 06:51:26 PM »
HI All,

I have just received my (2nd copy) Canon 24-70 f/2.8 mk II. Being a faithful CR follower and reading http://www.canonrumors.com/tech-articles/how-to-test-a-lens/ I begain from the top and followed ever step I could as best as I could. I also have Reikan Focal and ran through every testing option there was available. What I have found suprised me to the point I originally thought I had received the dreaded bad copy.

There is a definite focus shift on the 24-70 mk II. I have found that from f4 to f5.6 it starts to back focus severely  -5 afma vs +3 afma for f2.8 to f4 and +3 afma f5.8 on.

I am surprised there is not more information already out there on this.
I Found this on a competing forum  http://www.fredmiranda.com/forum/topic/1177402 very similar findings

I understand through research you can hold the DOF button down to get around this issue? But would that reduce effectiveness of the f2.8 cross focus points?

After a quick search it appears the Tamron 24-70 has a very similar focus shift issue. 
http://www.lenstip.com/340.5-Lens_review-Tamron_SP_24-70_mm_f_2.8_Di_VC_USD_Chromatic_and_spherical_aberration.html

Does anyone have any advice? At this point I don't know what to do?

Thank you for your time.

 
Either exchange it again, or send the lens to Canon for adjustment.  I'd say exchange it if you can.  It might have a issue at 70mm.
 
Due to residual spherical aberration,  a lens focus will appear to shift towards the rear, but the 24-70 should do it only very slightly.  For the most part, its just the depth of field that increases more towards the rear as you stop down.
You can decrease the aperture on this photozone chart and see it.
http://www.photozone.de/canon_eos_ff/773-canon2470f28mk2ff?start=1
 
http://toothwalker.org/optics/spherical.html


Thank you for your time on this. After spending a few more days with the lens (and since BH is closed for Passover). I have had some more time for testing. I have (am attempting to) uploaded 2 files both taken at f4 about 78 inches away. The live view has achieved perfect focus and has equal ticks before and after the target. The AF photo is back focused and has its first tick in focus behind the target. Before I return for a second time, I want to confirm this is not normal and I should at least see at least one tick in front of the target in focus.

Looking at the photozone review of this lens there is a focus shift, but their copy has 2 ticks in front and 10 behind at f4, (vs mine has no ticks in front).

As a side note, I really do love this lens. The colors are amazing! Everything at f/2.8 is amazing.
As a secondary side note: when I don't use the center focus point and use one of the f/4 or f/5.6 points, the back focus is not as prevalent. I will try to upload some pics of that too.
 
5DmkIII, 24-70 f/2.8L, 50 f/1.4, 70-200 f/2.8L, 430ex(I and II) 580ex I, 50D(backup and ML Video)

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Re: Canon 24-70 f/2.8L mkii Focus Shift
« Reply #11 on: March 31, 2013, 06:51:26 PM »