Zone Focusing

[Albert2]

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I have recently been shooting with a Summicron 35mm M ASPH. Deviating away from using the fast end of this lens I've tried shooting landscapes around the F11 Mark using the zone focusing option. As I was unsure at one point in the frame to focus using the rangefinder facility I opted for this method. I didn't know whether to focus on the foreground, midground or distance in order to get Ford Focus from front to back. Having set the infinity mark ( the centre of) exactly adjacent to the F11 mark on the right I knew the where the minimum distance then was. Anyway having then taken a few images when viewed on my Mac the distance parts of the image are not sharp. Distance in this case was a wall of housing about 70 m away. Any ideas please?

[Michael Geschlecht]

Hello Albert,

Welcome to the Forum.

Depth of field scales engraved on most lenses or provided in books are a set of guidelines that utilize criteria that some people do not find stringent enough for their purposes. Under any circumstances depth of field scales were NEVER meant to be take literally in all situations.

Some people use 2 stops smaller as their standard for acceptable sharpness, meaning: If the lens is set at F11: Only expect the portion bounded within the F5.6 lines (2 stops larger.) to be within acceptable sharpness.

Even this system does not always work as well as some people might like because the only plane of ACTUAL best focus is the image plane focused at using the range/viewfinder. Or on the focusing screen if using 1.

What some people do is focus on the most important image point & let the depth of focus fall where it may. In most instances that are not close ups that means that the in focus image will be APPROXIMATELY from 1/3 in front of to 2/3 behind the image point focused on. Varying in depth dependent on the F stop chosen for that specific lens. At very close distances (ie: 1 : 1) the depth of field is generally about the same on either side the actual plane of best focus.

The above information is not only for Leitz/Leica lenses but is usually the same with most lenses made by most manufacturers.

Best Regards,

Michael

Edited November 7, 2018 by Michael Geschlecht

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[a.noctilux]

Albert,

What you have is normal.

Circle of confusion "looseness".

The dof markings in Leica M lenses are heritage from the film use which has circle of confusion around 0.03mm (on film).

In digital (100% view on screen), Monochrom can resolve more than that old Standard.

 

edit :

Michael replied when I write this short explanation.

Edited November 7, 2018 by a.noctilux

[evikne]

Are you sure you actually remembered to set the aperture on the lens to f/11? I have experienced that when I have fiddled with the distance scale this obvious thing is possible to forget. 🙄

[jaapv]

Quoting Gunther Osterloh in a lecture: If you want the horizon to be sharp, focus on the horizon. A photograph is only sharp in one plane, the DOF is the zone of decreasingly acceptable unsharpneess. If youwant a photograph sharp from front to rear, you should use focus stacking.

[Alberti]

To confuse this a bit more, I have found with my 35mm (cron I even more the 40mm) that just the smallest movement will make or break the effect of having a lot of 'depth' at F5.6 what I mostly use. 

As I see it: The thickness of the sensor is so small, while in thick film emulsions there was a lot of latitude in focussing. 

 

Albert too

[Albert2]

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In the end I solved the issue. Flogged the M and bought a Q!!