topic Re: Focus shift with RF 100mm f2.8L macro lens in EF & RF Lenses

Focus shift with RF 100mm f2.8L macro lens

Bazsl — Sat, 15 Jan 2022 23:58:05 GMT

I have read a number of articles that discuss the focus shift problem with this lens. The only response I have seen from Canon was extremely brief and said that it was a design decision. I must be missing something because I cannot imagine any reason to buy any lens that exhibits focus shift as the lens is stopped down. The only work around that I have seen is to take a photo and, if it is out of focus, then manually focus in front of the desired focus point and use focus bracketing to take a series of photos and pick the one that has the desired point in focus. Why would I (or anyone) buy this lens instead of keeping their EF-100mm macro and sticking an adapter on the back. What am I missing?

Re: Focus shift with RF 100mm f2.8L macro lens

ebiggs1 — Sun, 16 Jan 2022 18:05:43 GMT

All lenses have a focus shift to some degree. It affects lens with faster maximum apertures the most. All lense are a compromise between physical lens factors and manufacturing abilities.

Re: Focus shift with RF 100mm f2.8L macro lens

Bazsl — Sun, 16 Jan 2022 20:31:26 GMT

All of which has nothing to do with the question. I have never read a review or article about the original EF 100MM f2.8 macro lens or the EF 100mm f2.8L macro lens that mentioned focus shift. However, there are numerous articles about the RF 100mm f2.8L macros lens that describe the focus shift problem with sample images. To me this suggests the focus shift of the RF 100mm f2.8L macro lens is severe enough to be very obvious and, therefore, a problem that no one would want to deal with. I certainly would not. I cannot understand why Canon would think anyone would want this lens given the reviews I have read. Clearly Canon engineers could have designed a lens without obvous focus shift since they have done so in the past. Please understand that I am not trying to troll the forum. I am a serious photographer looking for a factual answer.

Re: Focus shift with RF 100mm f2.8L macro lens

rs-eos — Sun, 16 Jan 2022 20:37:58 GMT

I'm not following. Are you saying you are acquiring focus at some aperture, then while that focus is locked in place, you are changing the aperture before you take the shot?

Or are you speaking to the lens back or forwards-focusing?

If the latter, does your camera allow for AF micro adjustments?

Re: Focus shift with RF 100mm f2.8L macro lens

Bazsl — Sun, 16 Jan 2022 20:54:45 GMT

I am shooting a R5. I do not own the RF 100mm f2.8L macro but considered buying it until I read several articles complaining about focus shift. According to my reading the problem is that the camera focuses with the lens wide open, in this case at f2.8. As always, when you trip the shutter release the lens stops down to the aperature set either by the automatic exposure system or by the user in manual mode. The problem accourding to the articles I have read is that when the the lens stops down the focus point shifts to a point behind the original focus point. This is more common at small f-stops (f8.0 and smaller) and high magnifications (close focusing distances). If you want more information do a search for "Canon RF 100mm macro focus shift" (without the quotes) and you will find serveral articles describing the phenomenon.

Re: Focus shift with RF 100mm f2.8L macro lens

jrhoffman75 — Sun, 16 Jan 2022 21:05:28 GMT

Discussed here:

https://www.the-digital-picture.com/Reviews/Canon-RF-100mm-F2.8-L-Macro-IS-USM-Lens.aspx

Re: Focus shift with RF 100mm f2.8L macro lens

Bazsl — Sun, 16 Jan 2022 21:24:52 GMT

Thanks jr. The article you referenced provides an excellent description of the problem.

Re: Focus shift with RF 100mm f2.8L macro lens

ebiggs1 — Mon, 17 Jan 2022 17:38:52 GMT

"All lenses have a focus shift to some degree." "... which has nothing to do with the question."

Ah, but it does. It explains why and what is happening. The original EF version has focus shift. Apparently it isn't as bad as the the new lens but it's there. Lenses that are prone to focus shift problems have more faster maximum apertures. Prime lenses with uncorrected spherical aberration will always have focus shift problems. All fast lens with aberration problems will exhibit some focus shift at different apertures. This is not new nor is it solely an issue with the lens in reference. Most, or I might say, all of the time the focus still lies in the acceptable focus range although perhaps not at the critical focus point.

Re: Focus shift with RF 100mm f2.8L macro lens

FloridaDrafter — Tue, 18 Jan 2022 22:20:03 GMT

I've been using the RF 100mm f/2.8 L IS USM on an R5 and R6 since September, 2021, with outstanding results, and never knew this "problem" existed until I read this post and followed John's link. When doing research, I didn’t look at extensive lab results, but rather images/videos taken with this lens by pros who shoot similar subjects and technique as me. I'm glad I bought it, it is a wonderful lens and I haven’t noticed the problem. I typically shoot between f/6.3 and f/16, mostly hand held but also some on tripod, AF hand held and MF on tripod for “posed” flowers. I also use this lens to stack.

Shot 1.4:1, cropped 50%, f/9, 1/500th, ISO 3200, slight editing in DPP. These orchids are 1/16".

Newton

Re: Focus shift with RF 100mm f2.8L macro lens

jrhoffman75 — Wed, 19 Jan 2022 00:28:15 GMT

Great shot Newton.

Re: Focus shift with RF 100mm f2.8L macro lens

Bazsl — Wed, 19 Jan 2022 00:33:48 GMT

See the article at https://www.the-digital-picture.com/Reviews/Canon-RF-100mm-F2.8-L-Macro-IS-USM-Lens.aspx posted by jr_hoffman. It explains the issue better than I did. I am shooting an R5. Mirrorless cameras do not have micro-adjustments because they do not need them since they focus on the sensor.

Re: Focus shift with RF 100mm f2.8L macro lens

FloridaDrafter — Wed, 19 Jan 2022 00:36:10 GMT

Thank you very much John! These are called Lawn Orchids (Zeuxine strateumatica).

Re: Focus shift with RF 100mm f2.8L macro lens

ebiggs1 — Wed, 19 Jan 2022 15:34:19 GMT

"(I) never knew this "problem" existed until I read this post and followed John's link."

This is the bottom line Newton. Is it really a problem? I say, no, not actually. This phenomenon has been around ever since lenses have been.

" I typically shoot between f/6.3 and f/16, mostly hand held but also some on tripod,..."

The problem isn't the final aperture you shoot at. It is the way most lenses work. You AF at wide open aperture and when you take the shoot at whatever aperture, the camera stops down. There is a slight difference in critical focus point between wide open, f2.8 and f8 lets say. Your flower is very nice and proves it really isn't a problem. If a person feels it is a problem, I suppose they can buy the EF version which I understand has less focus shift. I have the EF 100mm f2.8L and I never noticed the issue with it.

Re: Focus shift with RF 100mm f2.8L macro lens

Waddizzle — Wed, 19 Jan 2022 19:14:45 GMT

If the EF 100mm f/2.8L IS USM has focus shift, then I have never noticed it. More times than not, I am manually focusing from a tripod. When I do shoot handheld AF, then I am almost always using a crop sensor camera body, shooting at around f/4.

Re: Focus shift with RF 100mm f2.8L macro lens

ebiggs1 — Thu, 20 Jan 2022 15:49:58 GMT

If you have a f2.8 lens and shoot at f4 you are not likely to see much focus shift. One stop isn't likely enough of a change.

Re: Focus shift with RF 100mm f2.8L macro lens

ebiggs1 — Tue, 15 Mar 2022 14:15:29 GMT

The focus shift is between wide open AF and stop down shooting.

Re: Focus shift with RF 100mm f2.8L macro lens

PeteO — Mon, 04 Apr 2022 17:07:29 GMT

I am a Nikon and Canon shooter based in the UK. I bought the 100mm with the hope that I could sell my Nikon Z 105mm f4, as the Canon not only seemed a great macro lens but lighter than the Nikon to use as a portrait lens. However, I have found the Canon has a large degree of back focusing and cannot be used as an autofocus, run and gun, lens. The lens is as sharp as my Nikon 105 and I've done lots of testing, but the canon simply does not focus on the focussing point, with the area just behind the focussing point being in sharp focus. I have updated the firmware on my R5, but with no change to the lens performance. I will keep the lens, using manual focus for macro work. If anyone on this forum has a solution to using the lens, handheld and in autofocus mode, I would be very grateful, as I wanted to use it at my daughters upcoming wedding.

Re: Focus shift with RF 100mm f2.8L macro lens

Bazsl — Mon, 04 Apr 2022 19:24:46 GMT

I don't think manual focus will help since the problem, as described online, is that the focus shifts when the lens stops down at the time the photo is taken. The problem is not "back focus" as with a DSLR where a lens may not focus on the sensor plane. With mirrorless cameras the focus is always on the sensor plane since the focus detecting elements are built into the sensor.

Re: Focus shift with RF 100mm f2.8L macro lens

FloridaDrafter — Tue, 05 Apr 2022 05:04:56 GMT

Sorry you are having this problem and I wish I knew exactly what I am doing to avoid it. As I mentioned earlier in this post, I don't notice it in my day to day. I own the EF version as well and used it on the R5, then went straight from it to the RF with very few changes, mostly in post where I use a bit more unsharp masking. I hand hold and "run and gun" as you say, but do use a tripod on occasion. In fact, I shot several stacks today, 160 total shots in four stacks, and all of my starting points were dead on using AF at f/3.2, which in theory should show very little shift anyway. Generally when I'm shooting hand held, I use apertures ranging from f/8 to f/16. At f/16 it starts to get soft due to diffraction I'm sure. I also use high shutter speeds and higher than normal (for others) ISO. I do this (ISO) to keep my shutter up (I shake). For whatever reason, I don't notice focus shift. Since I own the EF version, I took my time researching this lens and bought it because of the outstanding reviews, sample images, and videos, none of which mentioned focus shift. Not that I doubt it exists, it's just that there seem to be lots of folks besides me who don't see it as an issue, or a deal breaker for that matter.

Once again, sorry you are having this issue. If you want, I have posted many shots with this lens and the R5 in the users photo section of this forum with EXIF info, so you may be able to glean some info from them that will help.

Newton

Re: Focus shift with RF 100mm f2.8L macro lens

PeteO — Fri, 08 Apr 2022 12:52:35 GMT

Thanks to all who have replied to my post. Unfortunately I have been suffering from Covid and only just felt like doing further tests. Bazsl's comment on manual focus got me thinking. So using a Bob Atkins chart on a 45 degree angle, I shot the lens in manual on a tripod. It was perfect. Then came tests using servo and single shots with varying types of focussing points on tripod and hand held. Spot focus on one shot, on tripod and hand held were extremely sharp, using servo took more care to get a sharp shot. My Nikon 105 f4 is much slower to focus than the Canon 100 f2.8 but tends to be accurate most of the time whereas, as mentioned, although much faster, the 100mm in servo needs a little more care. So another example of not the lens but the idiot behind it! I know this post is on the lens, but I must mention how brilliant a camera the R5 is, in particular the ability to set the AF-ON button to AF eye and also set the AE lock button to AF servo and set any focussing point. With that combination you are set for any focussing challenge. I wished my Nikon Z7ii could do the same, but then the R5 is almost twice the price. As regards my Nikon 105, I'm going to sell it along with my d850 and Nikon EF 70-200 f2.8 and buy the canon RF 70-200 f2.8, which will be, I hope, a more practical solution to photographing my daughter's wedding and other situations.

Thanks again for all the advice,

Pete