# Mirrorless and Focus Shift



## YuengLinger (Nov 6, 2018)

Can a mirrorless body make focus-shift issues a thing of the past?

I've done some research before asking here. I know from reading the manual that the EOS R, just as the 5D IV in Live View, has an Exposure Simulation feature that doesn't actually focus the camera at the selected aperture, but uses screen brightness as help in seeing what changing aperture will do to the exposure.

The Nikon D850, on the other hand, now seems to actually focus at the chosen aperture setting, and that is what the D850's Live View displays. The real thing, not a simulation.

I guess the EOS R and the 5D IV share more internals than just the sensor.

Zeiss addresses the issue a bit, but they leave Canon users hanging:

https://lenspire.zeiss.com/photo/en...performance-part-two-tips-and-best-practices/

If Nikon, on a dSLR can focus at the actual aperture setting, does that eliminate, or greatly reduce, focus shift problems on lenses that are prone to it?

I'm thinking of the ef 50mm f/1.2L. Wouldn't it be great if a mirrorless could correct for focus shift even through the EVF? (Sorry if this has been asked and answered already, but I didn't find such a thread.)


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## koenkooi (Nov 6, 2018)

YuengLinger said:


> Can a mirrorless body make focus-shift issues a thing of the past?
> 
> I've done some research before asking here. I know from reading the manual that the EOS R, just as the 5D IV in Live View, has an Exposure Simulation feature that doesn't actually focus the camera at the selected aperture, but uses screen brightness as help in seeing what changing aperture will do to the exposure.
> 
> ...



Someone mentioned on this forum, but I haven't been able to confirm it myself, that the R will use the configured aperture up to f/4.5-ish and stay on that for smaller apertures.

So the dreaded focus shift in the EF 50mm f/1.2 shouldn't be an issue on the R if that is true. 

Volunteers with an R and fast lenses (e.g. 1.8 or faster) are welcome to confirm or disprove the above


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## YuengLinger (Nov 6, 2018)

koenkooi said:


> Someone mentioned on this forum, but I haven't been able to confirm it myself, that the R will use the configured aperture up to f/4.5-ish and stay on that for smaller apertures.
> 
> So the dreaded focus shift in the EF 50mm f/1.2 shouldn't be an issue on the R if that is true.
> 
> Volunteers with an R and fast lenses (e.g. 1.8 or faster) are welcome to confirm or disprove the above


I'm looking forward to samples too, but the Zeiss video shows the focus-shift stays pretty bad even at f/8 when moving in close. For toddlers and just beyond, the distortion caused by being close with a 50mm can sometimes be a positive, thought not always. Their emotion can appear even more dynamic. I like still-life and detail shots close too. Which is why I've resisted many impulses to just get the EF 1.2L.

I've heard that further than six feet, the DoF conceals the focus shift. But I'd like to avoid it up close too.

But verification of what you heard, AF at up to f/4.5, would be great. I think 90% of any shots I'd take with the 50mm 1.2L would be below that, in the problematic range of f/2 - f/3.5.


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## Mt Spokane Photography (Nov 6, 2018)

My R focuses wide open and only stops down as you close the shutter. Exposure simulation does not change that. 

If the lens stopped down for autofocus, you would not be able to focus beyond about f/11.

I believe that the same issues exist for lenses with focus shift.


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## Viggo (Nov 6, 2018)

Could you not just hold the dof preview button down when focusing?

Besides, with the RF 50 available I would never spend money on a EF 50 for the EOS R


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## YuengLinger (Nov 6, 2018)

Viggo said:


> Could you not just hold the dof preview button down when focusing?
> 
> Besides, with the RF 50 available I would never spend money on a EF 50 for the EOS R


I do wonder if you can hold the DoF preview button and shoot. Never tried it on my 5D IV.
I really do want the R version of the 50mm, someday, but if the issue of focus-shift were eliminated as a "con" with the EF version, paying $1000 less might be worth considering. I know it is soft in comparison, but not horribly so, and it is lighter and shorter. And cheaper. Did I already mention cheaper?


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## Larsskv (Nov 6, 2018)

YuengLinger said:


> Can a mirrorless body make focus-shift issues a thing of the past?
> 
> I've done some research before asking here. I know from reading the manual that the EOS R, just as the 5D IV in Live View, has an Exposure Simulation feature that doesn't actually focus the camera at the selected aperture, but uses screen brightness as help in seeing what changing aperture will do to the exposure.
> 
> ...



Theoretically speaking, I guess so. What I can tell you is that focus shift is a problem on the EOS R and EF 50 L f1.2. When stopping down to f3.5 it constantly back focuses. I believe my 1DXII and 5DIV has some correction for that, because I didn’t find focus shift to be an much of an issue on the 50L before I got the EOS R.


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## YuengLinger (Nov 6, 2018)

Larsskv said:


> Theoretically speaking, I guess so. What I can tell you is that focus shift is a problem on the EOS R and EF 50 L f1.2. When stopping down to f3.5 it constantly back focuses. I believe my 1DXII and 5DIV has some correction for that, because I didn’t find focus shift to be an much of an issue on the 50L before I got the EOS R.


Interesting. Puzzling!


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## Pooshoes (Nov 7, 2018)

Rf 50 is a fast focus lens as well


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## padam (Nov 7, 2018)

If they use the same DPAF algorithm as they do in the movie mode, then it can be eliminated.
Because it is focusing at the current aperture value both in servo AF or single if servo AF is disabled.
But for some reason this is kept separate and pictures cannot be taken in that mode.

I guess one could back button focus with that, then switch it into stills mode and take the picture. This has been kept especially easy on the EOS R (...)


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## Mt Spokane Photography (Nov 7, 2018)

Viggo said:


> Could you not just hold the dof preview button down when focusing?
> 
> Besides, with the RF 50 available I would never spend money on a EF 50 for the EOS R




There is no DOF Preview button. I started looking, and found that you must go into the menu and assign a button. So, II assigned the M-Fn and stopped down the lens, but AF would not work. Apparently AF is locked out when the assigned DOF Preview button is depressed, so you might be able to manually focus the lens, but it would not be friendly to try that.

With the new RF lenses containing information about the lens characteristics and sending them to the camera, it is conceivable that corrections could be made for focus shift. I don't think its the case though.


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## Larsskv (Nov 7, 2018)

Mt Spokane Photography said:


> There is no DOF Preview button. I started looking, and found that you must go into the menu and assign a button. So, II assigned the M-Fn and stopped down the lens, but AF would not work. Apparently AF is locked out when the assigned DOF Preview button is depressed, so you might be able to manually focus the lens, but it would not be friendly to try that.
> 
> With the new RF lenses containing information about the lens characteristics and sending them to the camera, it is conceivable that corrections could be made for focus shift. I don't think its the case though.



I am sure RF lenses will be compensated for focus shift, but I don’t see why Canon would do it for EF lenses in future R bodies. It could hurt RF lens sales.


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## Mt Spokane Photography (Nov 7, 2018)

Larsskv said:


> I am sure RF lenses will be compensated for focus shift, but I don’t see why Canon would do it for EF lenses in future R bodies. It could hurt RF lens sales.



The problem doing it in body is obvious, new ones are added after bodies are released, and the body does not change or have the right info. The cost of issuing new firmware for every body would be pretty high, and most users would not update in any event. Canon does update lens tables occasionally along with firmware updates to add new lenses or make corrections, but never on any kind of regular basis.

With characteristics being in the lens, it is a elegant solution. Since I've also read of reviewers finding focus shift exists with the 50mm f/1.2 RF, it seems to still exist. The good news is that the cause of focus shift, Spherical Aberration, is low in the new lens, so its detectable but not a major issue any longer. That lens does sound like a really good one.


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