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Archive 2018 · Calibrated some lenses/TC interesting findings

armd
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p.1 #1 · p.1 #1 · Calibrated some lenses/TC interesting findings

For a birthday present, I decided to treat myself to Reikan's Focal, the (semi) automated method for MA of lenses (cheap date, I know). Prior to this, the conflict over the numerous variables (tolerances, reproducibility, changes in lighting, temperature, etc.) and my field experience had left me rather unconvinced that MA could make a pivotal difference in achieving critical sharpness. Generally, my L lenses perform reasonably well and my prior sessions with Dot Tune and other methodologies suggested that my lenses were focusing fairly accurately. So what did the experience with Focal reveal?

First, my lenses were as I had observed, focusing accurately and they required minimal MA (-1 to +2). The process became more interesting was once I repeated the testing with TC's attached (for example a 1.4x III). What I have noticed when shooting with my Canon TC's attached to my otherwise accurate lenses is that the AF consistency just disappears. I'll often experience huge swings in BF/FF with seemingly no apparent explanation. These TC's, 1.4x and 2.0x III's have been sent to CPS, were returned as being "in spec" and yet still perform less than optimally in real life circumstances. Well, today, my testing with Focal seemed to confirm my observations and the focus consistency was all over the map. Is this common and what does this say about Canon TC's?

Sample from a 100-400 IS II + 1.4x III TC at 540mm

Apr 10, 2018 at 10:24 PM

technic
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p.1 #2 · p.1 #2 · Calibrated some lenses/TC interesting findings

You don't mention what body you were using for these tests which is relevant. I'm pretty sure there are differences between e.g. FF and APS-C DSLR bodies.

On my 80D the 100-400II requires major MFA corrections once it is focused closer than 5 meters or so, up to about -20 near MFD. Only at long distance a setting of around 0 is fine. Several others have reported similar findings here, mostly with recent APS-C bodies. There is no way to correct for this on Canon cameras/lenses (some Sigma and Tamron lenses can adjust MFA for focus distance). This "backfocus" problem may be less severe with FF cameras (which could be related to the different PDAF module) but it is difficult to be sure because most people never check and simply ignore or deny the problem.

When using 1.4TCIII my experience is that it often requires some MFA (with 100-400II, 2.8/200, 4/300IS), which is to be expected because every lens design is different. I haven't seen a huge decrease in AF consistency with TC mounted, however you are making things more difficult for the PDAF module (less light etc.) so some deterioration should be expected.

I have seen major PDAF consistency problems when working with different color temperatures like the red light of the setting sun, but it's difficult to check such things because the conditions are never the same and there might be other variables that influence AF accuracy in that case.

Apr 11, 2018 at 02:14 AM

armd
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p.1 #3 · p.1 #3 · Calibrated some lenses/TC interesting findings

technic wrote:
You don't mention what body you were using for these tests which is relevant. I'm pretty sure there are differences between e.g. FF and APS-C DSLR bodies.

On my 80D the 100-400II requires major MFA corrections once it is focused closer than 5 meters or so, up to about -20 near MFD. Only at long distance a setting of around 0 is fine. Several others have reported similar findings here, mostly with recent APS-C bodies. There is no way to correct for this on Canon cameras/lenses (some Sigma and Tamron lenses can adjust MFA for focus distance). This "backfocus" problem may...Show more →

The camera body in question was a 5dmkiv, i.e. FF. In some ways you've highlighted my difficulty with MA. While the lenses require little if any MA when tested statically (including the 100-400 II IS (+1, +1) at various distances, there are clearly other factors which affect AF consistency including ambient temperature, light temperature, etc. As the graph listed above indicated, AF consistency dropped significantly with the TC and this is what I have observed in practice.

Apr 11, 2018 at 06:46 AM

Sy Sez
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p.1 #4 · p.1 #4 · Calibrated some lenses/TC interesting findings

From Canon:
"The adjustments applied using this control are based on the depth-of-field you'd have at a lens's maximum aperture. They are not based on the lens's focal length! When setting the Microadjustment, you'll see a scale on the camera's LCD monitor with up to + or - twenty steps. Each step is a very fine increment, equal to 1/8th of the depth-of-field you'd have with the current lens wide-open. And that 1/8th of the depth of field is only moving forward (toward the camera) or back (toward the background) from the sharpest plane of focus. The main thing to remember here is that these are very fine increments. Don't expect radical shifts in focus with adjustments like plus 3 or minus 5."

This indicates that MFA of +3 to -5 would be completely insignificant, especially on a lens with a Max aperture of F5.6, and not likely to make any difference as to keeper rate with a in-spec, body, & lens.

Having said that, my tests with a 7D-2 /100-400l-2, required no MFA, but with the 1.4lll, appeared in my testing to benefit from a -5 MFA "T" / 0 "W"

Apr 11, 2018 at 10:42 AM

technic
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p.1 #5 · p.1 #5 · Calibrated some lenses/TC interesting findings

armd wrote:
The camera body in question was a 5dmkiv, i.e. FF. In some ways you've highlighted my difficulty with MA. While the lenses require little if any MA when tested statically (including the 100-400 II IS (+1, +1) at various distances, there are clearly other factors which affect AF consistency including ambient temperature, light temperature, etc. As the graph listed above indicated, AF consistency dropped significantly with the TC and this is what I have observed in practice.

MFA in its current state is a crude and often ineffective solution for a complex problem ... it's one of the issues where mirrorless theoretically has a clear advantage, at least as long as the subject isn't moving too fast. I guess most people who say they never need it are less critical, ore only use the camera in relatively narrow range of conditions.

Apr 11, 2018 at 11:48 AM

pjbishop
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p.1 #6 · p.1 #6 · Calibrated some lenses/TC interesting findings

At a tangent to the main topic, I have been wondering whether in fact the extender IIIs were actually better than the earlier ones in respect to resolution. I had a II ( 1.4x ) that did very well on the 70-200 f/4 IS, but sold that combo, now have the 2.8 IS II version of the zoom with the III 1.4 extender. I haven't yet used the extender - this info is interesting

Apr 13, 2018 at 02:22 PM

armd
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p.1 #7 · p.1 #7 · Calibrated some lenses/TC interesting findings

pjbishop wrote:
At a tangent to the main topic, I have been wondering whether in fact the extender IIIs were actually better than the earlier ones in respect to resolution. I had a II ( 1.4x ) that did very well on the 70-200 f/4 IS, but sold that combo, now have the 2.8 IS II version of the zoom with the III 1.4 extender. I haven't yet used the extender - this info is interesting

Well, my field experience is that the 1.4x III is marginally better than the II with the added bonus that it has better AF speed with advanced lenses.

Apr 13, 2018 at 07:17 PM

armd
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p.1 #8 · p.1 #8 · Calibrated some lenses/TC interesting findings

Here's an update...

After discussing with Reikan, the focus inconsistency seemed way out of order. The first series were performed out of doors during a sunny afternoon so I figured that perhaps environmental factors such as wind, changing light conditions, and perhaps some light leak into the view finder (yes, I covered the view finder with tape) could have affected the results. After moving indoors with constant studio lighting, the results were much more consistent. See below. The true test will be taking the lenses out into the field and seeing whether the MA makes a difference.

Zoom Lens with 1.4x iii TC

Prime Lens with 2x iii TC

Apr 13, 2018 at 07:24 PM

pjbishop
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p.1 #9 · p.1 #9 · Calibrated some lenses/TC interesting findings

Armd, even more interesting- thanks. I also sometimes use the extender on the 135 f/2.

Apr 14, 2018 at 08:37 AM

Zenon Char
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p.1 #10 · p.1 #10 · Calibrated some lenses/TC interesting findings

Sorry for the long post but I have always found MFA and very inserting but odd creature.

I tried to start a survey a few years ago about this but it did not go very well. Sans TC my 100-400 II need s very little if any MFA. When the Canon 1.4 III goes on Focal tells me +13 with the 7D2 at 420mm and +9 with the 5D4 at 560mm. I was wondering how many others were experiencing this.

Normally when I get those types of numbers with just the lens or body it goes back to Canon. That has happened only once with a 70-200 2.8 II. Canon found a mis-calibrated board. Not much you can do when the TC throws it out. If I had it calibrated at Canon then it would be off without the TC.

Over the years I have had a lot of heat for my views about extreme MFA requirements and sending lens or camera back to Canon. In the case of my 70-200 people told me if it needs +15 then just set it there. Two Canon USA techs told me MFA is for emergencies and encouraged me to send that lens. Of course we use it to fine tune our gear. I'm not going to send it back if it needs +4.

I have always felt that way about it before talking to Canon. This is a preemptive bit about my personal views on this

Each to his/her own and I don't want to justify it again. Done that too many times. A few years ago I found this which made me realize I'm not the only one. Section 11.

https://photographylife.com/how-to-calibrate-lenses

I was curious as to why this was happening. Although the 100-400 II is TC compatible I learned that TC's are tuned for long primes. Article about this.

https://wordpress.lensrentals.com/blog/2009/01/teleconverters-101/

We know that there are specs that have a perfect point and lower/upper tolerances of said point. Lot's of elements and moving parts in a zoom so I can only conclude it is within spec but slight deviations within that spec are amplified with a TC. I don't know for sure. No two lenses are alike. Could be the TC itself and maybe I should have retuned it but I don't get that huge swing on my 300 F4 IS. +3 without and +6 with. I'm getting good images with the 100-400 II but not sure if my keeper rate is effected.

It took me two days of shooting a $20 bill, staring at the screen, second guessing myself, etc before I came with those MFA values for the 100-400. FoCal did it in a few minutes. I never liked lens align. I have tried pretty much every method out there. I don't want to judge, I want something to tell me what to do. Some people are really good at it. I think Teamspead has a homemade lens align setup. Others just use 3 batteries.

This was good method by Arash but Canon removed Quick View in DPP 4.

http://arihazeghiphotography.com/MA-web/

Another good article by Arash

http://arihazeghiphotography.com/blog/focus-micro-adjustment-is-it-always-needed/

This article blew me away. I had a lot of respect for Chuck but he said this is our method but if you can do better go for it. What? I purchase thousands of dollars of precision equipment designed by your engineers. You tell me the correct method

http://digitaljournalist.org/issue0812/tech-tips.html

I have numerous links on the subject. Even Canon has been all over the place. One article says 50X the focal length, another to do it at the distance you normally shoot and another at location. At location is basically the distance you shoot at but not often practical. If you like Dot Tune it would be easier. Last time I chatted with Snapsy he was doing at infinity. Roof tops, street signs. I found it was inconsistent which I concluded was my fault. I don't like to MFA outdoors.

This is Canon's latest. The first time they talk about the lighting environment and to MFA at the distance you normally shoot at. If you can't then use 50X. Finally a more sensible explanation. Long before I found this I was using two daylight balanced studio CFL's to light the target.

Page 5

http://www.learn.usa.canon.com/app/pdfs/articles/AF_MicroAdjustGuide_desktop.pdf

Last wrench in the works. Liquidstone MFA's at MFD and you can't argue with the results. I read about a company in Europe that MFA's long primes at 21 ft or so.

Here is FoCal's take on this which is interesting. Currently I have a place that just meets the minimum distance for 560mm.

Page 2

http://s449182328.websitehome.co.uk/focal/dl//Docs/FoCal%20Test%20Distance_1.1.pdf

Apr 14, 2018 at 10:38 AM

armd
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p.1 #11 · p.1 #11 · Calibrated some lenses/TC interesting findings

Thanks for posting the detailed information and links. I am sure that others will find them useful. What I've been puzzled by is why all of my lenses which function fine without much MA (-1 to +2 at most) are registering +8 or +9 with TC's. Interestingly, both v iii TC's have been back to Canon for "calibration" and they keep telling me they are in spec.

Ultimately, I use the settings as starting points which I then tweak in the field under the particular lighting, distance, temperature, etc.

Apr 14, 2018 at 07:52 PM

Zenon Char
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p.1 #12 · p.1 #12 · Calibrated some lenses/TC interesting findings

I did not realize Canon could calibrate a TC. Thanks for that info. As for tweaking in the field you have far more patience than I do.

Apr 14, 2018 at 09:42 PM

armd
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p.1 #13 · p.1 #13 · Calibrated some lenses/TC interesting findings

Zenon Char wrote:
I did not realize Canon could calibrate a TC. Thanks for that info. As for tweaking in the field you have far more patience than I do.

It's not all that difficult. Usually, I find an object on a field, a stick, post, etc. at the approximate distance I anticipate shooting and check the AF accuracy. It takes just a couple of minutes at most and usually pays off. The biggest challenge is not so much the change in light temperature but the direction. I notice the greatest changes with back or strong side lighting and those are difficult to anticipate when shooting wildlife.

Apr 15, 2018 at 07:41 AM

lighthound
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p.1 #14 · p.1 #14 · Calibrated some lenses/TC interesting findings

I've been curious about the need to AFMA my 1.4xIII + 100-400II. I've done it by using the simple D cell battery set-up but I'm wondering if it's actually doing anything in real world shooting.

On my FF body I'm @ 560mm f/8 and most of my targets while shooting wildlife are at least 100 feet away. At this distance the DOF is nearly 6 feet. If at f/5.6 this would drop it to about 4 foot.
I'm not sure these micro adjustments even come into play on long glass. Does it?

Apr 15, 2018 at 05:01 PM

melcat
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p.1 #15 · p.1 #15 · Calibrated some lenses/TC interesting findings

armd wrote:
What I've been puzzled by is why all of my lenses which function fine without much MA (-1 to +2 at most) are registering +8 or +9 with TC's.

Hypothesis: microfocus adjustment with a teleconverter compensates for variations in the physical length of the teleconverter tube as well as just the optics. And that could also be affected by how tightly each of the two bayonet joins (camera–teleconverter and teleconverter–lens) is made. This would also explain why microadjustment has to be done between camera/lens pairs and not each of the camera and lens individually.

Apr 15, 2018 at 08:50 PM

technic
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p.1 #16 · p.1 #16 · Calibrated some lenses/TC interesting findings

lighthound wrote:
I've been curious about the need to AFMA my 1.4xIII + 100-400II. I've done it by using the simple D cell battery set-up but I'm wondering if it's actually doing anything in real world shooting.

On my FF body I'm @ 560mm f/8 and most of my targets while shooting wildlife are at least 100 feet away. At this distance the DOF is nearly 6 feet. If at f/5.6 this would drop it to about 4 foot.
I'm not sure these micro adjustments even come into play on long glass. Does it?

You may be using the wrong procedure: the 100-400II has significant backfocus for closer subjects, which becomes visible around 5 meters or so and progressively gets worse towards MFD. Mine has exact AF for near-infinity subjects but needs about -20 near MFD. So if you are calibrating with a relatively close subject your long distance shots will be significantly off (and the other way round ...). There is no way to get the right calibration for the whole range. This is without the TC, adding the TC requires a minor adjustment on my system (-5 or so). Just for the record: this is what I find on my 80D, and others with recent APS-C bodies have confirmed similar findings. Values might be different on FF bodies due to different AF system.

DOF isn't relevant, what is relevant is if the focus is consistently off and if you can see the improvement of the AFMA .

Apr 16, 2018 at 11:15 AM

armd
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p.1 #17 · p.1 #17 · Calibrated some lenses/TC interesting findings

technic wrote:
You may be using the wrong procedure: the 100-400II has significant backfocus for closer subjects, which becomes visible around 5 meters or so and progressively gets worse towards MFD. Mine has exact AF for near-infinity subjects but needs about -20 near MFD. So if you are calibrating with a relatively close subject your long distance shots will be significantly off (and the other way round ...). There is no way to get the right calibration for the whole range. This is without the TC, adding the TC requires a minor adjustment on my system (-5 or so). Just for the...Show more →

You are absolutely correct, and I've experienced tremendous back focus with closer subjects (<10 meters or so) at 400mm. But to the poster's points about DOF v. AF accuracy, while they are certainly relevant they are not interchangeable. Remember DOF is the range of "acceptable" focus. Acceptably sharp is not the same as ideally sharp and what one regards as "acceptable" may not be sufficient for other users. While he is correct that the DOF becomes progressively larger (all things being equal) the greater distance one is away from the subject, so too as the subject becomes smaller in the frame, the prospects for AF errors increase as well (atmosphere effects, AF point overlap, etc.). So, yes, while distance can be favorable with respect to DOF, it's not always kind to AF accuracy. Finally, does AF accuracy come into play with long glass? Absolutely! I have plenty of images with a 600mm f/4 lens with and without a TC where critical AF was not obtained due to MA errors.

Apr 16, 2018 at 01:35 PM

Zenon Char
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p.1 #18 · p.1 #18 · Calibrated some lenses/TC interesting findings

I was not aware of the back focus this lens has. Without the TC the 5D4 needs +1 and the 7D2 needs +4 at 400mm. With TC +9 and +13. MFA done at 10 meters which is Focal's minimum distance.

I was about 2-3 meters from this bird with my 5D4. Focus on the head

Apr 16, 2018 at 01:59 PM

Zenon Char
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p.1 #19 · p.1 #19 · Calibrated some lenses/TC interesting findings

Well this is interesting. Without a TC focus is pretty accurate with the simple battery test. Without the TC at 3 or 10 metres it is pretty much dead on. With the TC it is dead on at 3 metres but back focuses at 10 meters. Not much but you can see it.

I have always thought so and it seems that a TC (or mine) can really throw that lens out of whack. I know of people who had to just their MFA their lenses a little with the TC. I had been thinking about this for a while and I I'm going to go back to my 7D2 this summer. I always had great results but I like the IQ better with my 5D4. Not sharpness, just the look of the images.

I think I'll give that TC a rest until I get my long prime. Maybe I'll try the 5D4 sans TC but I think pushing the crops will diminish the gains.

Apr 16, 2018 at 02:57 PM

Max10
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p.1 #20 · p.1 #20 · Calibrated some lenses/TC interesting findings

Apr 17, 2018 at 02:35 AM

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