topic Re: Different microadjustments needed for far and close focusing in EF & RF Lenses

EF 100-400 Mark II Different microadjustments needed for far and close focusing

Tostra97 — Tue, 13 Aug 2024 13:24:54 GMT

Yesterday I got myself a Canon 100-400 mkII for my 5D mkIV. Today I took it for test drive, and I had some issues with the autofocus overshooting by quite a bit, so I went home and did some microadjustments. It needed 8-10 clicks backwards, but that got it working perfectly at close range. Then I tried focusing far away and realized that it now focuses too close, it only needs something like one click at 30 meters.
Is there a way to fix this? I know the Sigma 150-600 mm has the option to do different microadjustments at different distances, is there an "extended" microadjustment option like that for the 5D? Or a different focus mode or setting that will make it focus more accurately?
I will be using the lens both for close-ups of insects as well as birds far away, so I really need it to work at both ends.

Re: Different microadjustments needed for far and close focusing

Tostra97 — Sun, 11 Aug 2024 16:20:38 GMT

I have realized that I was being stupid. I was focusing through a window, so that was the reason I had such bad focus at a distance. I would still like to know if this option exists though, as I would like to fine-tune, and I also have a different lens which has a problem like this.

Re: Different microadjustments needed for far and close focusing

Waddizzle — Sun, 11 Aug 2024 16:32:41 GMT

If you made AFMA adjustments, then the answer to your question was staring you in the face. You should have seen two AFMA setting for your zoom lens, “W” and “T”. These letters stand for “wide” and “telephoto”. You could have made two adjustments. One at 100mm for the W setting and another at 400mm for the T setting.

I recommend leaving them alone and resetting your adjustments back to zero. Making the focus adjustments is deceptively difficult. It is far easier to get it wrong, than it is to get it right. It is just as much a test of your skills as a photographer as it is your gear.

There are several factors that need to be taken into consideration that most people never think about. For example, what distance should your focus target be from the camera?

Re: Different microadjustments needed for far and close focusing

Tostra97 — Sun, 11 Aug 2024 16:58:04 GMT

I may have been unclear... I did the adjustments both at wide and tele of course, but exactly as you say, the distance was the issue. A close subject was in focus at 400 mm, while a far subject was apparently not, but I realized that the far subject was not sharp because I had taken the picture through a window. I went outside, and the far away subject was sharp.
I did the adjustments at a range which seemed appropriate for a duck-size subject using a high-contrast printed box next to a slanted ruler, and then I re-adjusted at a close range where the missed focus was most notable on my trip. Like I said, it needed about 10 clicks, so it was quite severe imo, and I do believe it works much better now, as the focus behind my subjects was a real pain on my trip today, and now it is reliably focusing.

However, my question is if an option exist to adjust at several distances, say 1, 5, 20 and 50 m. I have seen that the Sigma 150-600 mm can be adjusted like that using the console, so maybe it exists for Canon lenses as well?

Also, please enlighten me about the many factors and considerations? I realize that you advie against adjusting on youor own, but I am willing to spend a lot of time to get this lens working its best, so if I have missed something, I would very much like to know so I can improve on it. I believe a lot of hobbyists share that opinion, especially when getting expensive gear, so it might help some people if you share your thoughts on this 🙂

Re: Different microadjustments needed for far and close focusing

Tronhard — Sun, 11 Aug 2024 18:10:32 GMT

There are a lot of factors that impact on what is in focus: achieving a sharp image is a collaboration between the optical precision of the lens, the focusing system of the camera and its configuration, and the skill of the photographer.

As you admit, shooting through a window, which is a chunk of glass with no real quality control from an optical point of view (was it single pane or double glazed?) is not conducive to accurate results. The factory camera lens configuration is done under clinical conditions where temperature, humidity, air movement and light are all controlled: yours are not. Thus, in the real world all of these will change and they impact on the image your lens will capture. But unless your lens is grossly defective, by far the greatest variation in sharpness of image will be from how your focusing system is set up in-camera, and how you use it.

Simply relying on the focus you have adjusted is also not a constant - Bill (Waddizzle) has already made the suggestions for how to consider two settings for very close and very far. If this seems crude, there are reasons for this. Canon do not make a docking station for their lenses, because they make lenses only for Canon cameras, while 3rd party makers design for multiple brands, thus a Sigma lens will not have the facility to do in-camera micro-adjustments and uses the method you may have seen on You Tube, for example. Canon don't need such a device because they can provide adjustments in camera and they can be configured by camera firmware.

This is done in-camera for JPG files by in-camera correction software - you will find an item in the focusing menu set to have that turned on - it usually is. However, when you bring your RAW images into post-production software, that software itself will make adjustments to the focus and a set of other configurations according to algorithms provided by Canon, or created by Adobe, for example.

I was shooting a couple of days ago with that same lens and watched the images change as the lens corrections were applied to the RAW images in post. This is normal practice for modern lenses. However, you could compromise those corrections by trying to anticipate them - lens corrections are best made at the extremes of focus and then let the correction algorithms do their job. In all my four decades of photography, I have never felt it necessary to micro-adjust a lens - and my standards are high too as I used to sell my images.

Right now you are using the excellent EF 100-400L MkII lens, which is a relatively heavy, expensive unit because it relies predominantly on glass to get optical clarity. With the newer lenses across all camera makers, there is now a trend to create much cheaper, lighter lenses that rely less on purely optical perfection and now use computational photography algorithms developed by AI to perform dynamic mathematical image corrections - which can be altered or improved by firmware updates. This is particularly true for lenses at wide angles, where distortions and vignetting are the biggest issue, and that resulted in lenses traditionally were massive, heavy and cost a lot of money. One example is the excellent RF 14-35L f/4 lens. Without corrections it has massive distortions and vignetting, but with corrections on, it is tack sharp and square. Again, those corrections are turned on by default in camera and applied automatically in most PP software, and the results look excellent with them applied.

As I said, how you focus will have a huge impact. Default settings will tend to focus on the closest object within a specified focus area. The wider the focus area the more objects that encloses. With wildlife that is quite often not the subject's closest eye, which is the critical element. Thus, I have been shooting single-point centred Back Button Focus to get absolute precision of focus location. I focus on the eye, lock focus (which is always in servo mode), recompose and shoot. If the subject is moving, I hold the AF-ON button to track, if it is static I just tap it to lock it.

I used to have the 5DIV but have sold it, but in the last couple of days was shooting hand-held, in available (dim or contrasty) winter's light with the EF 100-400LII on the even more demanding 52MP 5DsR, and these are some of the results. The insect was shot through glass at the zoo, while the bird shots of the wood pigeon were in dense, dark bush. Image shot RAW, corrected using PS auto corrections, adjustments made for lighting levels, cropped and massively downsized to post here.
EOS 5DsR, EF100-400II@220mm, f/5.6, 1/125sec, ISO-1600 EOS 5DsR, EF100-400II@300mm, f/6.3, 1/250sec, ISO-800

EOS 5DsR, EF100-400II@400mm, f/7.1, 1/30sec, ISO-1600 EOS 5DsR, EF100-400II@400mm, f/5.6, 1/50sec, ISO-1600EOS 5DsR, EF100-400II@400mm, f/5.6, 1/320sec, ISO-250 EOS 5DsR, EF100-400II@321mm, f/5.6, 1/250sec, ISO-400

Re: Different microadjustments needed for far and close focusing

Waddizzle — Sun, 11 Aug 2024 18:18:57 GMT

I suspect Sigma includes all those calibration points because their lenses are inferior. I do not see where you gain anything by using so many calibration points, especially in light of the fact that you can adjust the focusing range of the AF Limiter switch.

[EDIT] The rule of thumb for what focusing distance to use is to use the shooting distances and focal lengths that you expect when using the lens. If you want a generic distance to use, then calibrate at 25-50x the focal length in use. I recommend using 50x the focal length for super telephoto lenses.

If you are using any filters when shooting or calibrating, then that is a problem. The rule of thumb for that lens is not to use any UV, ND, to CPL filters with it.

Re: Different microadjustments needed for far and close focusing

wq9nsc — Sun, 11 Aug 2024 18:26:58 GMT

I have a lot of Canon glass and I have never run into an issue where micro-focus was an issue once dialed in at a "normal" point in the range. But I have also never needed to use an offset of more than 4 to dial in a lens to any of my bodies so I would be a little concerned about needed a 10 point bias. Canon does not provide two settings for different distance, only for the two ends with a "zoom" type lens.

If you are following the procedure in one of the Canon micro focus guidebooks, a faster and easier method is when starting with a new lens take test shots using three offset points each side of 0 (along with 0 thus ending with 7 sets from the first test). So for example, take 3 shots each at 0, +1, +3, +5, -1, -3, and -5 and examine all of these as a group. DPP will show the offest in the EXIF data making it easy to track.

Based upon your results, your second run will be easy since you would interpolate with another set of test shots between the two best focus values. This is MUCH faster than using the original Canon approach of taking the test shots, examining, and then trying again. I can dial in a new lens to the 7 bodies I actively use in under 30 minutes using this method.

Rodger