The focus distances of the M ring do not correspond to the result on an SL2?

[Arcantide]

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Good morning (and sorry for my poor english)

,
I take the liberty of contacting you concerning the use of an M lens mounted (21mm f/3.4 super-elmar) on an SL2 with the adapter ring.

I have the impression that the measurements displayed on the lens focusing ring do not correspond to reality.

For example, if I set my center point to 1.70m for an aperture of 8, I should be "sharp" from 90cm to infinity.
In reality, the area of sharpness is incredibly reduced than that.

In a Leica Store in Paris, a technician told me that on a digital camera like the SL2, you have to remove between 1 and 2 apertures to know the real zone of sharpness.

So, the lens focusing measurements for a f/8 should be taken as if the aperture was set on f/4?
Can you confirm this for me? Have you ever noticed this difference between the area of sharpness of the hyperfocal and the actual rendering to the image?

Thanks for your lights
See you soon.

[andybarton]

20 minutes ago, Arcantide said:

In a Leica Store in Paris, a technician told me that on a digital camera like the SL2, you have to remove between 1 and 2 apertures to know the real zone of sharpness.

Welcome to the forum.

The technician is correct - I always judge depth of field on the focus ring from a couple of stops wider. I use an M camera, by the way. The depth of field on M lenses has always been set for use on film cameras, where the true aperture is used to judge.

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[Arcantide]

9 minutes ago, andybarton said:

Welcome to the forum.

The technician is correct - I always judge depth of field on the focus ring from a couple of stops wider. I use an M camera, by the way. The depth of field on M lenses has always been set for use on film cameras, where the true aperture is used to judge.

Many thanks for your answer! 🙏

[pop]

18 minutes ago, Arcantide said:

For example, if I set my center point to 1.70m for an aperture of 8, I should be "sharp" from 90cm to infinity.

The depth of field scale on the lens is calculated according to rules which are now nearly a century old. It was calculated on the assumption that you would make a print of - perhaps - 18x24 cm which you then would look at from a distance of an arm's length. Also, the sharpness of photographic images then was not comparable to what we are accustomed to today.

You have to make your own experience for what you consider sharp enough for the kind of images you take and present.

[jaapv]

Also the high resolution of the SL2 will create a very narrow zone of DOF when the image is viewed at 100% due to the high magnification. 

[helged]

28 minutes ago, andybarton said:

I always judge depth of field on the focus ring from a couple of stops wider.

Exactly what I do, even with the 21mm Super-Elmar-M. 

And certainly, don't blindly trust the DOF scale on the focus ring when using M on (any) mirrorless body, the SL included. Partly because of the adapter being used. 

[PCPix]

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It seems the OP may be doing scale focusing with their 21mm, which many others would also do on an M body for street or architecture - however something important to consider is that the thickness of the adapter makes M lenses focus ‘beyond infinity’ on the SL series bodies, so the distance scale will be slightly off, i.e. lens scale set to 1.7m will actually be focused a little further out in reality.

This compounded with not allowing the generally accepted ‘extra two stops’ for depth of field estimation on a high res sensor would definitely put the near boundary of acceptable focus further away than expected.

To get the desired result in the example set in the OP’s question they would need to focus through the viewfinder on a subject at 1.7m and then stop down to f/16. 

A quick check on my SL2, SEM 21mm shows infinity (at f/3.4) through the viewfinder needs the lens scale to be just beyond the 5m mark - not an insignificant amount of focus ring difference. 

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[jaapv]

I would like to quote Günther Osterloh:” If you want a sharp horizon, focus on the horizon. “