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Archive 2012 · Lens micro focus adjustment experiences?
  
 
Suresh T
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p.1 #1 · p.1 #1 · Lens micro focus adjustment experiences?


So last weekend I played around with lens MA, partly to see if it even mattered for my camera/lenses...

1. Printed out test charts available free online (e.g. http://www.bealecorner.org/red/test-patterns/ISO_12233-reschart.pdf) and following Canon's recommendations (e.g. http://www.pixel-shooter.com/forum/showthread.php?t=21099)...
2. Experimented with DIY lens microadjustment suggestions, like http://regex.info/blog/photo-tech/focus-chart
3. Tried arash_hazeghi's trick using Canon's EOS utility, a tethered setup, and live view (http://www.birdphotographers.net/forums/showthread.php/58042-AF-microadjustment-tricks)
4. Variation of #3 above, but taking shots after each < or > microadjustment in EOS utility's live view window

Below are some observations based on 24-105L (on a 5D2)...

For an f/4 lens, doing microadjustment _without_ a "45 degree ruler" approach is very very difficult since there are at least 5-10 adjacent microadjustment settings where the sharpness is indistinguishable. This is especially true if you follow Canon's official recommendation of using a target distance of 50x the focal length.

For example, the smallest DOF for the 24-105L with the 50x recommendation is 1.75 ft at 105mm (and f/4) with a target distance of 16.4 ft. 2 ft of DOF means a _lot_ of identically sharp images you'll likely see with various MA's (even at 100% crop).

So approaches #3 and #4 simply didn't work for me. Maybe they'd work with a faster lens...

Then I tried #2, even though Canon recommends the target plane must be parallel to the sensor plane. And for now, I also resorted to using close to MFD to reduce the DOF as much as possible. Success finally! At f/4, 105mm, and a target distance of a little over 2 ft, the MA was +8 for the 24-105L.

Some questions:

- Has anyone had a "better" experience with an f/4 like the 24-105L using DIY approaches?
- Why does the target plane need to be parallel to the sensor plane (per Canon)? Is it just to get reproducible AF results?
- Why does Canon's instructions suggest using the longest focal length (of a zoom lens), then also recommend using the "most commonly used" focal length? (And if there's such a thing as a most commonly used FL, wouldn't everyone just use a prime at that FL instead? :-))
- Why does the target need to be 50x away? (25x away according to some non-Canon sources, e.g. LensAlign.) What if MFD is used? Shouldn't we pick the "most commonly used" target distance instead? :-)
- Even with "perfect" micro adjustment, if there are differences in the MA at different focal lengths, what setting does one pick?

I can see that MA matters most with a shallow DOF (fast and/or long lens), or if the lens is badly misaligned (for the camera).

I've decided to order LensAlign Mk II and wait for it before checking MA on my other lenses. (FoCal is not for me, since the more hands-on the better. :-))

My approach with LensAlign will be to try and measure the MA at different focal lengths (e.g. 24, 50, 70, 105mm for the 24-105L) and distances of MFD/25x/50x. If the MA is very different, I'll lean towards using the setting for the longest focal length (which I _will_ use) and the "smallest commonly used" :-) distance, since the DOF will be the shallowest there, and so will matter the most there.

What has been your experience with lens MA?


Edited on Jun 13, 2012 at 07:42 AM · View previous versions



Jun 13, 2012 at 07:02 AM
Ferrophot
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p.1 #2 · p.1 #2 · Lens micro focus adjustment experiences?


I think people get too wound up over acheiving the last micro inch of accuracy with MA. It's there if you are having problems with front/back focussing, as I was. I think people will just end up chasing butterflies if they try and get perfect results at all focal lengths on all their lenses. I used a pretty rough and ready method, looked at my shots, said that's front focussed and moved it a bit for that lens. Took a few more shots and moved it a bit more. I still check focus on all my shots, but if it looks good at 50% or 100% that's good enough for me.
I've only really needed to do it for my 100-400L, but also adjusted the 85mm using the same method even though I didn't think I could see any misfocus.
Although my rough and ready method can just pick the difference between +5 and +6 I find there's more than enough variables when AFing to swamp the difference between these points (subject movement, camera movement, point of focus on a 3 dimensional subject).
Then again I might be a sloppy photographer who is just lucky with focus.



Jun 13, 2012 at 07:27 AM
Suresh T
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p.1 #3 · p.1 #3 · Lens micro focus adjustment experiences?


Ferrophot, I agree about overdoing the MA. For my 24-105L, it certainly didn't seem worth it. I suspect it may be more interesting on my 70-300L or 85 1.8, I'll find out soon.

For me however, the learning that goes with the tinkering is more fun/important than any minor sharpness improvement in my photos. :-)



Jun 13, 2012 at 07:50 AM
Ferrophot
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p.1 #4 · p.1 #4 · Lens micro focus adjustment experiences?


Suresh, Must admit I get enjoyment from tinkering too, just doesn't extend to focus. Most of my shots are of moving objects, stopping motion blur is my little obsession.


Jun 13, 2012 at 10:52 AM
twistedlim
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p.1 #5 · p.1 #5 · Lens micro focus adjustment experiences?


Suresh T wrote:
Ferrophot, I agree about overdoing the MA. For my 24-105L, it certainly didn't seem worth it. I suspect it may be more interesting on my 70-300L or 85 1.8, I'll find out soon.

For me however, the learning that goes with the tinkering is more fun/important than any minor sharpness improvement in my photos. :-)


I am not going to waste the time with my 24-105 and 70-300L since the images are crisp and sharp wide open on everything I have shot. The 85 1.8 is worth doing but so far none of my lens have required more than 2 one way or the other so I am satisfied. My experiences are as follows (pretty much the same my 5d2 although I have only used fo-cal with the 35 1.4 so far):

5D3
35 1.4 +2
35 2.0 +1
50 1.1 +2
85 1.8 0
85 1.2 +1




Jun 14, 2012 at 12:23 PM
Suresh T
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p.1 #6 · p.1 #6 · Lens micro focus adjustment experiences?


twistedlim, I mostly agree about skipping the 70-300L as well, although at 300mm, f/5.6 and < 20 ft, the DOF is pretty shallow, so I'm curious if it will make a difference. Mostly I will focus on the 85 1.8, 50 1.8 and 100 2.8. LensAlign Mk II should arrive next week.


Jun 15, 2012 at 06:04 AM
bboule
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p.1 #7 · p.1 #7 · Lens micro focus adjustment experiences?


My 24-105 f/4L IS definitely doesn't seem to need it.. you're pretty much always operating with enough depth of field on that lens to not notice if it's off a little.. I have a 17-40 f/4L and that one always seems to have plenty of depth of field as well.

On my 5D3 my 28/1.8 and 85/1.8 seem to be perfect. I can't remember but I may have them at +/- 1 or 2 though.

It's just my 50/1.4 that clearly needs AF Microadjust.. and I haven't gotten it right yet, although it is at something like -8 right now. I have a 300 f/4L IS and a 100mm f/2.8 Macro (non-L) as well, and although those are very often operating at shallow depth of field, I haven't seen any problem that leads me to believe I should bother trying to adjust it.



Jun 15, 2012 at 03:46 PM
Suresh T
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p.1 #8 · p.1 #8 · Lens micro focus adjustment experiences?


bboule wrote:
On my 5D3 my 28/1.8 and 85/1.8 seem to be perfect. I can't remember but I may have them at +/- 1 or 2 though.

It's just my 50/1.4 that clearly needs AF Microadjust.. and I haven't gotten it right yet, although it is at something like -8 right now. I have a 300 f/4L IS and a 100mm f/2.8 Macro (non-L) as well, and although those are very often operating at shallow depth of field, I haven't seen any problem that leads me to believe I should bother trying to adjust it.


Interesting how there's so much variation in lens needing MA. It tells me that it's not the camera or the lens by itself, but the unique combination of the two.

If that's the case however, why does the 5D2 even have the option to adjust by the same amount for all lenses? Does anyone actually use that setting?



Jun 15, 2012 at 04:01 PM
mco_970
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p.1 #9 · p.1 #9 · Lens micro focus adjustment experiences?


I highly recommend Reikan's FoCal software. It is MUCH easier than anything else you are doing to get good MA results.

My 24-105 is at:
0 on 5D2
2 on 7D
-4 on 1D3

... and it's tack sharp on all 3 bodies. It was not sharp at all on my 5Dc when I had it.



Jun 15, 2012 at 04:40 PM
Photon
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p.1 #10 · p.1 #10 · Lens micro focus adjustment experiences?


Suresh T wrote:
Interesting how there's so much variation in lens needing MA. It tells me that it's not the camera or the lens by itself, but the unique combination of the two.

If that's the case however, why does the 5D2 even have the option to adjust by the same amount for all lenses? Does anyone actually use that setting?

Canon (and others) introduced MA because there is inevitably manufacturing variation from body to body, and lens to lens. Yes, it is the combination of the two that determines whether adjustment is worthwhile or unnecessary, but it is also very possible for a camera to be "within specs" yet off enough that an adjustment "for all lenses" of 3 or 4 points could improve wide open results with all of them. If you have more than two or three lenses, though, they are somewhat likely to have enough variation among them that calibrating MA for individual lenses will be helpful. Of course, you could have just two lenses that happened to be "off" in opposite directions, so the individual approach would be the only one that made sense.

I have a number of lenses that AF beautifully at 0 on 5D3, a number that benefit from a few points adjustment. The same goes on other bodies, though the amounts of MA vary. I have one lens that requires a hefty MA on all bodies. I'm sure it could stand to be factory adjusted, but with MA, it AFs fine on 5D3, 5D2, 1D4, 1D3. Sure, it saves Canon from some of the demands for service adjustment, but I'm glad to have the facility built into the newer bodies.

I tend to adjust zooms at or near longest FL (5D3 allows MA at tele and wide settings), I use a high contrast, detailed chart (flat and square to camera!), and use distances within my normal shooting range, usually less than 50xFL for long teles, and sometimes more than that for wide angles.



Jun 15, 2012 at 04:49 PM
 

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Photon
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p.1 #11 · p.1 #11 · Lens micro focus adjustment experiences?


Michelle's suggestion is good. I'm waiting for Reikan to issue FoCal for Mac!
Meanwhile, for me the resolution chart I'm using works. I can definitely see differences in small adjustments with an f/4 lens. I think the DOF calculators or tables you've looked at are "optimistic", i.e. based on prints viewed from "normal" distance, not pixel peeping or holding a large print close to you.



Jun 15, 2012 at 04:54 PM
speedmaster20d
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p.1 #12 · p.1 #12 · Lens micro focus adjustment experiences?


Suresh,

MA is mostly for macro or super telephoto where DOF is narrow and critical focus is important. With a lens like 24-105 you won't achieve much by spending your time trying to adjust it. If you want to use 24-105 for closeups forget about it and buy a proper macro lens for best results such as the 100 f/2.8 macro IS.

Even if you achieve MA for one focal length it might be a bit off for other FLs. The tolerance in AF itself is a few units in MA scale, especially in AI-servo so going from 0 to like -2 on a 24-105mm f/4 lens is not really meaningful.

In the article I used 24-105 for demonstration only because it was easier to setup, I wouldn't care about MA on that lens. Many people become too obsessed with MA, most of the time MA is not really needed.



Jun 15, 2012 at 05:15 PM
StillFingerz
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p.1 #13 · p.1 #13 · Lens micro focus adjustment experiences?


mco_970 wrote:
I highly recommend Reikan's FoCal software. It is MUCH easier than anything else you are doing to get good MA results.

My 24-105 is at:
0 on 5D2
2 on 7D
-4 on 1D3

... and it's tack sharp on all 3 bodies. It was not sharp at all on my 5Dc when I had it.


Thank you, just got a used 50D, my 1st time to use MA. So it will just be hit-n-miss with my 40D; glad I've not seen any focus/sharpness issues wit it so far...I think



Jun 15, 2012 at 05:22 PM
Suresh T
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p.1 #14 · p.1 #14 · Lens micro focus adjustment experiences?


Photon wrote:
Michelle's suggestion is good. I'm waiting for Reikan to issue FoCal for Mac!
Meanwhile, for me the resolution chart I'm using works. I can definitely see differences in small adjustments with an f/4 lens. I think the DOF calculators or tables you've looked at are "optimistic", i.e. based on prints viewed from "normal" distance, not pixel peeping or holding a large print close to you.


Michelle/Photon, FoCal sounds perfect for busy pros. For an amateur like myself, I had fun tinkering with my initial DIY MA approach, so I've ordered LensAlign for now, since I think it may also give me a better understanding of the DOF and sharpness of my lenses. The downside is that it may take all day, or I don't do it right. :-)

Photon, what resolution chart do you use? The online charts I printed (at a high dpi) didn't seem "good enough" to tell a small MA change on my 24-105L (I needed an MA change of 5 or more to easily tell the difference at 100% crop). I'm also considering the Edmund Resolving Power Chart (http://www.edmundoptics.com/testing-targets/test-targets/resolution-test-targets/resolving-power-chart/1665).



Jun 15, 2012 at 05:24 PM
Suresh T
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p.1 #15 · p.1 #15 · Lens micro focus adjustment experiences?


speedmaster20d wrote:
Suresh,

MA is mostly for macro or super telephoto where DOF is narrow and critical focus is important. With a lens like 24-105 you won't achieve much by spending your time trying to adjust it. If you want to use 24-105 for closeups forget about it and buy a proper macro lens for best results such as the 100 f/2.8 macro IS.

Even if you achieve MA for one focal length it might be a bit off for other FLs. The tolerance in AF itself is a few units in MA scale, especially in AI-servo so going from 0 to like
...Show more

Thanks speedmaster20d, if I play around with the 24-105L's MA, it will only be to learn about the lens itself. I do have and enjoy the 100 2.8 Macro, so much so that I may later upgrade to the L IS version for the IS (which may have helped occasionally). :-) I plan to MA the 100 2.8 Macro.



Jun 15, 2012 at 05:33 PM
Imagemaster
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p.1 #16 · p.1 #16 · Lens micro focus adjustment experiences?


Simple method:





#1

  Canon EOS-1D Mark IV    300mm    f/2.8    1/4000s    1600 ISO    -0.3 EV  




Jun 15, 2012 at 06:13 PM
Imagemaster
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p.1 #17 · p.1 #17 · Lens micro focus adjustment experiences?


First shot easily showed on LCD screen that 300 f2.8 non-IS lens was front-focusing. MA of +20 seems a lot, but not surprising for a lens this old.

Next four are crops pasted next to each other for easier comparisons:





#2







#3







#4







#5




Jun 15, 2012 at 06:16 PM
Suresh T
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p.1 #18 · p.1 #18 · Lens micro focus adjustment experiences?


Imagemaster wrote:
First shot easily showed on LCD screen that 300 f2.8 non-IS lens was front-focusing. MA of +20 seems a lot, but not surprising for a lens this old.

Next four are crops pasted next to each other for easier comparisons:


Nice method! Now that I think about it, LensAlign won't work on long lenses (without the long ruler, which is extra $$), so this may be the best method for me. :-)

What distance did you shoot these at, it seems less than the "50x focal length" suggested by Canon, and I've been wondering how I'd shoot 50 ft away at 300mm on my 70-300L.



Jun 15, 2012 at 06:34 PM
mco_970
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p.1 #19 · p.1 #19 · Lens micro focus adjustment experiences?


Cost of FoCal is about the same as LensAlign. You will go crazy from MA after a while, trust me on this.

But the good thing is you can sell your LensAlign in the buy and sell section and get FoCal to see how much time you wasted taking photos of test charts (I friggin' hate taking photos of test charts!).

Suresh T wrote:
Michelle/Photon, FoCal sounds perfect for busy pros. For an amateur like myself, I had fun tinkering with my initial DIY MA approach, so I've ordered LensAlign for now, since I think it may also give me a better understanding of the DOF and sharpness of my lenses. The downside is that it may take all day, or I don't do it right. :-)

Photon, what resolution chart do you use? The online charts I printed (at a high dpi) didn't seem "good enough" to tell a small MA change on my 24-105L (I needed an MA change of 5 or
...Show more



Jun 15, 2012 at 07:11 PM
Suresh T
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p.1 #20 · p.1 #20 · Lens micro focus adjustment experiences?


Michelle, you're making me doubt my LA order. :-) I may well swap it out for FoCal later, if it becomes just a tedious thing, we'll see.


Jun 18, 2012 at 06:49 AM
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