Test: RF 100L macro f/2.8 on focus shift. I see NO issue!

[Nemorino]

There is a lot of talk about focus shift of the RF 100L macro. I have used the lens without any issues and have been wondering a long time what's that talk is about.
So I have made four series of pictures with changing aperture.
Subject is a dead hummingbird moth I found and which is pefect for a "real life" test.
I put the camera on a tripod with a macro rail to focus, connected it to my PC. Focus set to manual, IS off.
Electronic shutter and 10s delay to prevent shake. After focussing I didn't touch the camera and set everything via PC.
The focus is set on the eye like in real life by using the 15x preview.


For every magnification I first post the uncropped picture at f/2.8 and f/32.

First 1:1.4 or better mfd



And 1:1 crops 2758x1551
f/2.8


f/4

f/5.6

f/8

f/11

f/16

f/22

f/32


The DLA of the R5 is f/7.1 so @ f/8 und higher thegeneral sharpness decreases but still the eye is the most sharp subject. I see no focus shift issue.

 

[Nemorino]

1:1 magnification
The f/32 picture is darker because of the time limit of the electronic shutter.



The following are 1:1 crops of 1895x1066px


f/2.8


f/4


f/5.6


f/8


f/11


f/16



f/22


f/32

 

[Nemorino]

For lower magnification I cannot tell precisely the ratio as there is no mark in the R5 display.

2:1



1:1 crops of 1536x864px

f/2.8


f/4


f/5.6


f/8


f/11


f/16


f/22


f/32

 

[Nemorino]

For the last series I missed the shots at f/22 and f/32.
The uncropped pictures are f/2.8 and f/16 @ about 3:1



1:1 crops of 1536x864px

f/2.8


f/4

f/5.6



f/8


f/11


f/16

 

[koenkooi]

Thanks for doing such a comprehensive experiment! I personally haven't noticed the focus shift either, but I'm most of the time way past f/8, so I can't confidently say it isn't their either.

I wonder if there's a sample to sample variation for the SA shift calibration, because I don't think Bryan from TDP would mention this in the review if it wasn't there.

 

[danfaz]

Nice experiment! I have noticed the shift on mine. Similar to Bryan at TDP, I setup a piece of paper with text at an angle, shot at apertures from 2.8 to 11, and noticed the in-focus letters gradually move. This doesn't happen at further distances, though.

 

[neuroanatomist]

Canon’s engineers have acknowledged that the RF 100/2.8 exhibits focus shift as a necessary design compromise for achieving 1.4x magnification.

I suspect what we’re seeing here is the difference between a controlled test intended to identify a specific issue (angled ruler) versus a ‘real world’ test. Most likely (as has been suggested by others) the focus shift problem may not be all that much of a problem.

Personally, it is one reason I have not bought the lens, albeit a minor one. The main reason is my EF 100/2.8 does the job up to 1x, and when I need more I have the MP-E 65.

 

[Del Paso]

Thanks Nemorino!
You almost convinced me to give this lens a try.
And if the borders at infinity setting (landscapes!) are better than the ones of the EF 2,8/100 L ...
I don't use or need the 1,4 X magnification anyway. Thanks to your extensive testing I already know that F 11 will be my most used diaphragm.

 

[Del Paso]

Thanks for doing such a comprehensive experiment! I personally haven't noticed the focus shift either, but I'm most of the time way past f/8, so I can't confidently say it isn't their either.

I wonder if there's a sample to sample variation for the SA shift calibration, because I don't think Bryan from TDP would mention this in the review if it wasn't there.

I too tend to believe in SA control induced sample variation.

 

[Nemorino]

I wonder if there's a sample to sample variation for the SA shift calibration, because I don't think Bryan from TDP would mention this in the review if it wasn't there.

I don't think the SAC has any effect on the focal plane.

 

[koenkooi]

I don't think the SAC has any effect on the focal plane.

Someone on the fredmiranda forum described how he got rid of his focus shift issues by setting the SA control slightly beyond zero.
Since my lens doesn’t seem to be suffering from focus shift, I can’t test that myself

 

[Nemorino]

Canon’s engineers have acknowledged that the RF 100/2.8 exhibits focus shift as a necessary design compromise for achieving 1.4x magnification.

IMO most fast lenses (wider/equal f/2.8) exhibit focus shift if we focus wide open but we do not notice it as the DoF increases in front of and behind the focal plane. This graphic has ben posted in another thread:

The DoF probably only increases less in front of the plane compared to a "perfect" lens.

But on my posted pictures the hairs in front of the eye get sharper the tighter the aperture is. So the issue is to small to be seen in "normal" use. I have about 9000 pictures shot last year with an aperture tighter f/8 and the RF 100L macro and have not noticed it.

 

[Nemorino]

Someone on the fredmiranda forum described how he got rid of his focus shift issues by setting the SA control slightly beyond zero.

IMO pure nonsens

 

[Nemorino]

Since my lens doesn’t seem to be suffering from focus shift, I can’t test that myself

I don't think there are copy variations as this is based on the wide opened aperture as the graphic I just posted shows.

 

[SwissFrank]

The DLA of the R5 is f/7.1 so @ f/8 und higher thegeneral sharpness decreases but still the eye is the most sharp subject. I see no focus shift issue.

Excellent research. You've used yours 100x more than I've used mine but I've looked for focus shift both at 1:1 or so and at 4m and cannot detect any.

What's DLA?

 

[Nemorino]

What's DLA?

Sorry for the late reply!
DLA = diffraction limited aperture

Diffraction-Limited-Aperture

What is Diffraction Limited Aperture (DLA)? And why you need to know what your camers's DLA is.

www.the-digital-picture.com