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There is an ice storm in Washington, D.C. this morning.  So perhaps taking the new 50 Summilux out for a spin will have to wait.  But here is what I was able to capture on my front step this morning, without venturing so far out onto the glaze that I might break my neck, or my new lens...

 

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And remember, I am locked in my house due to an sheet of ice out there...

 

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Braved the ice for this one...

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Yes. It seems to be the characteristic that Dr Karbe is going for (at least since the APO 50mm): more sharpness at point of focus but faster fall-off. The main limitation that I am finding is that the SL's AF is unreliable (at least in low winter light). So you may as well manual focus a smaller lens and be sure you have a shot.

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The depth of field is purely a factor of sensor size, aperture and distance, and nothing to do with lens design (provided the aperture is accurately recorded). All 50mm lenses will have identical depths of field taken at the same aperture and distance, on a given sensor.

 

That is basic physics.

 

Fall off, plane of best focus, corner sharpness, lpi and out of focus character will, conversely, vary a lot, but not depth of field.

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Well Dr Karbe claims to have confounded basic physics and, e.g., the new Summicrons will look as if they have the depth of field of a Summilux. The recent lenses certainly have a different look from earlier lenses. I still like the extravagant bokeh of the M Summilux, but this lenses is much more restrained.

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The depth of field is purely a factor of sensor size, aperture and distance, and nothing to do with lens design (provided the aperture is accurately recorded). All 50mm lenses will have identical depths of field taken at the same aperture and distance, on a given sensor.

 

That is basic physics.

 

 

 

Actually this gross generalization is only true for ideal optics with perfect Guassian symmetry. Asymmetrical design and non-ideal real world applications fortunately make the world a less boring place.

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Well Dr Karbe claims to have confounded basic physics and, e.g., the new Summicrons will look as if they have the depth of field of a Summilux. The recent lenses certainly have a different look from earlier lenses. I still like the extravagant bokeh of the M Summilux, but this lenses is much more restrained.

Sophistry, unless the Summilux is wider than 1.4 and the Summicron not really f/2. What he may be talking about is the point of best focus (not sure that's actually possible) or fall off, giving the impression of a shallower depth of field.

 

Why would that be a good thing?

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Actually this gross generalization is only true for ideal optics with perfect Guassian symmetry. Asymmetrical design and non-ideal real world applications fortunately make the world a less boring place.

Generalizations are inherent in short posts. "Gross" is pejorative, but unsupported - we're talking physics, not non-ideal real world applications, Gaussian or otherwise. It is quite fair to say that a lens may deal with the transition from in focus to out of focus in different ways, but it is a fallacy to say that an f/1.4 lens has a shallower depth of field than any other (all things being equal).

 

If there is any simplistic statement it is that the SL-50 has a shallower depth of field. That's just silly - any depth of field calculator will show that in a heartbeat.

Edited by IkarusJohn
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Sophistry, unless the Summilux is wider than 1.4 and the Summicron not really f/2. What he may be talking about is the point of best focus (not sure that's actually possible) or fall off, giving the impression of a shallower depth of field.

Why would that be a good thing?

I assume that he is talking about what you refer to as fall off. You can see the effect in one of the M lens forum threads where the 75mm Summilux at f1.4 appears to have a wider depth of field / slower fall off than the 75mm Summicron at f2. It appears to be a good thing because the sharpest point is even sharper. (Which is cause and which effect I'll leave to the physicists. )

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We mentioned earlier today that there was an ice storm in Washington.  Once it was safe to get out of the house, we wandered over to the nearby Bishop's Garden at the National Cathedral, SL and new 50 Summilux in hand.  Here are some images that, with better resolution that can be posted here, gives you a sense of this special lens.  

 

https://tulipfrenzy.com/2016/12/17/the-ice-storm/

 

For a flavor of what we were able to do with this lens, here's an image:

 

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Can someone point me to where Dr. Karbe claimed to confound basic physics? I'm aware of David Farkas' interview with Dr. Karbe http://www.reddotforum.com/content/2016/09/setting-a-new-standard-with-leica-sl-lenses-a-discussion-with-peter-karbe-at-photokina-2016/, but I haven't understood exactly what was meant by 

 

 

The sharpness DOF curve, which you can visualize as a parabola, has been changed from what you have seen in the past. We’ve tightened and raised the curve, so that f/2 will offer a look that is similar to f/1.4. It is very unique and special. And, at the same time, will offer greater sharpness at the point of focus. The contrast of in focus and out of focus will be more pronounced, which produces a very 3D effect.

 

Is Dr. Karbe saying the sharpness DOF curves of the f/2 SL Summicrons will be similar to the sharpness DOF curves of f/1.4 lenses? (Not the images, but the curves?)

 

Are these sharpness DOF curves he is talking about like the ones shown in figures 1 and 2 here: http://www.edmundoptics.com/resources/application-notes/imaging/depth-of-field-and-depth-of-focus/ ?

 

dgktkr

Edited by dgktkr
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Yes. It seems to be the characteristic that Dr Karbe is going for (at least since the APO 50mm): more sharpness at point of focus but faster fall-off. The main limitation that I am finding is that the SL's AF is unreliable (at least in low winter light). So you may as well manual focus a smaller lens and be sure you have a shot.

 

Could you be a bit more specific abouth the "AF is unreliable"?

Is this in context of the 50? Given it's size and price I would really expect it to exceed in this regard, otherwise the 50 apo should be the 50 of choice.

 

the 90-280 was quite good, the 24-90 might have some issues. However I'm yet to see a proper AF system for shallow depth of field Portraits(best being Hasselblad truefocus). 

One of the reasons I bought the SL, because it allows to MF properly. Sadly with some limitation, the fuji does it better with a constant focus magnification point. Not sure about the Sony behaviour.

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