SL Lenses ...Understanding Depth of Field

[glenerrolrd]

Watching the Leica Videos about the SL Prime lenses ...Peter Karbe makes a point about how the lenses have been designed to create a shallow DOF . When compared to other Leica lenses ...the MTF peaks higher but also has a narrower footprint . This is intentional and Karbe points to the F2 sum microns creating a bokeh similar to an F1.4 lens .

While I have seen this in the past ..I always expected that I had probably front focused a bit . Certainly its a lot easier to see with the newer high MP cameras .

I realize that many lenses suffer form various degree of field curvature and focus shift ....which makes placing the plan of focus somewhat of guess work (unless you can use live view at the shooting aperture ). The other issue is that optimum micro contrast is normally achieved at F5.6 and sharpness limiting diffraction kicks in even at F8 . Some of this can retrieve with post processing sharping . So its easy to see why this difference could be missed .

Two thoughts worth considering :

1. Do some lenses have significantly different DOF at a give focal length and aperture . I had never heard this before . ???

2. Assuming Karbe is correct ..how does this affect the choice of Leica SL lenses for specific applications . Certainly provides an opportunity for a shallow DOF wide open which would be favorable for portraits, fashion even limited sports . Definitely workable for street and most travel .

But what about landscape where many want to shoot at F11 to obtain near to far sharpness ...seems to be going in the wrong direction ? Pushes you toward "focus stacking " to achieve enough DOF .

 

[Paul2660]

So far I have found the DOF of the 24-90 to be impressive on the wide side, I have not used any of the primes, (cost of each is a bit staggering).
One thing I have asked Leica tech support/customer support is why the SL2 has no focus stacking capabilities in camera, which is pretty much a standard feature all modern mirrorless cameras, 35mm or Medium format. It should not be a hard thing to add in firmware. I have heard rumors of a stacking feature added for a tethered environment, (like to C1), but not a stand alone. Tethered is not where I want to be in the field.

Paul

 

[fmueller]

High resolution sensors almost demand focus stacking to keep diffraction losses minimal. I recall my GFX100 would start showing diffraction losses beyond f8/f11. Nonetheless, I've only done limited focus stacking with a GFX100 (no longer owned) and my current Hasselblad CFVII 50C. My short take is that outside "in the field", when the end of your focus stack is often at infinity, it is much easier to simply make a few frames at different distances and let helicon focus do its thing in post. I learned that through side by side comparison of automated vs. manual stacking. Only when getting closer to min focus distance of a lens does focus stacking (focus bracketing in Hasselblad terms) using in camera settings seem to come out ahead. YMMV.

 

[Paul2660]

Fully agree. However unlike most camera sold today the SL2 or SL2s have no ability to take the necessary frames automatically. Yes it can be done manually but that for me slows down the process and makes a hand held stack impossible. With the latest versions is helicon I can often get a nice series of images 8 or less that will blend together. Panasonic’s S1R has this capability so for Leica it’s just a matter of firmware implementation and want to do it the latter of which they don’t seem to have much interest in.

Paul