2/50mm Summicron-SL

[IkarusJohn]

Advertisement (gone after registration)

Scott wrote - “Remember DoF is a subjective effect” ...

 

My understanding is that depth of field (the area of best focus) is an absolute. As a matter of physics, for a given circle of confusion, aperture and focusing distance, the depth of the plane of best focus will be predictable regardless of the lens. There’s nothing subjective about it, is there?

 

Fall off and what the out of focus area looks like is certainly subjective, and will depend on lighting and the nature of the out of focus areas. I find most Summiluxes have a very creamy out of focus treatment (not so much the 35 Summilux-M FLE), and the 50 Summilux-SL particularly so. I have the Summilux-M ASPH, Noctilux and Summillux-SL and while each has its different strengths, as a overall lens, the SL-50 is far and away the best of them.

 

Never really gelled with the 90 field of view. Perhaps rightly or wrongly, my subjective view of the out of focus treatment of short teles and longer lenses is that the “bokeh” can often appear a bit harsh.

 

Do the 75 and 90 Summincron-SL lenses have the abrupt fall off that tends to go with shallow depths of field at longer focal lenghts, and busy and distracting out of focus treatment?

 

Cheers

John

Edited August 11, 2018 by IkarusJohn

[scott kirkpatrick]

Scott wrote - “Remember DoF is a subjective effect” ...

 

My understanding is that depth of field (the area of best focus) is an absolute. As a matter of physics, for a given circle of confusion, aperture and focusing distance, the depth of the plane of best focus will be predictable regardless of the lens. There’s nothing subjective about it, is there?

 

Fall off and what the out of focus area looks like is certainly subjective, and will depend on lighting and the nature of the out of focus areas. I find most Summiluxes have a very creamy out of focus treatment (not so much the 35 Summilux-M FLE), and the 50 Summilux-SL particularly so. I have the Summilux-M ASPH, Noctilux and Summillux-SL and while each has its different strengths, as a overall lens, the SL-50 is far and away the best of them.

....

Mike Johnston did a list of all the factors that lead to "DoF" in an final image a few days ago:  http://theonlinephotographer.typepad.com/the_online_photographer/2018/08/readers-weigh-in-on-the-olympus-25mm-%C6%9212-and-the-pentax-hd-fa-50mm-f14-sdm-aw.html .  You have to look down in the comments after a long post. There are technical factors, more complex than the geometrical picture of light rays spreading out from a dot into a circle, and a lot of issues in how the image proceeds into pixels, demosaiced and then rendered and viewed.  And while we can stare at MTF charts that show the contrast across the image field at various f-stops for our favorite example lenses, no one publishes the same information for the images just out of focus.

 

My assumption is that there are two basic design philosphies for Leica lenses, the Summilux-asph and the APO Summicron, and that the SL generation will follow those two paths.  Comparing similar scenes shot with both the M 50's of the two schools, or perhaps the Mandler 75/80 SX versus the APO SC 75 or 90 would be a good guide to comparing how each separates objects just before or after the image plane.  That separation into planes, rather than "buttery smooth" removal of the background without artifacts, is what I want.

Edited August 12, 2018 by scott kirkpatrick

[Advertisement]

The Leica Q3 is available for pre-order at B&H Photo Video and Adorama

[IkarusJohn]

I’m not sure who is comparing MTF charts for DoF calculations.

 

I was looking purely at the physics of the calculation (rather than perception - image size, processing, viewing distance etc). There have been excellent papers linked in other threads on DoF calculation.

[AndreaP75]

I’m using both lenses (SL 50 and SL 90) for low light and portraits. Both have their strengths and really no weaknesses, at least optically speaking.

 

Shooting wide open with the SL 50 you have the typical lux rendering, but with very high sharpness and definition of the focus point, at any shooting distance. I think this carachteristic is what gives the images a medium format look. Stopping it down to f2, you are at the level of the 50 APO M.

 

The SL 90 gives its best at shorter and medium shooting distances, where the 3D effect is even more pronounced than the SL 50. I’m not referring to bokeh rendering, it’s about how the subject stands out of the background. At longer shooting distances, the images are still extremely sharp, even wide open, but it obviously looses that special appeal.

 

The upcoming SL 50 cron may address only portability with possibly slightly higher shrpeness between f2 to f4. And of course, faster autofocus.

 

However, going SL 50 cron would probably leave an open door for a 50 Noctilux, at least for the rendering.

[helged]

I’m using both lenses (SL 50 and SL 90) for low light and portraits. Both have their strengths and really no weaknesses, at least optically speaking.

 

Shooting wide open with the SL 50 you have the typical lux rendering, but with very high sharpness and definition of the focus point, at any shooting distance. I think this carachteristic is what gives the images a medium format look. Stopping it down to f2, you are at the level of the 50 APO M.

 

The SL 90 gives its best at shorter and medium shooting distances, where the 3D effect is even more pronounced than the SL 50. I’m not referring to bokeh rendering, it’s about how the subject stands out of the background. At longer shooting distances, the images are still extremely sharp, even wide open, but it obviously looses that special appeal.

 

The upcoming SL 50 cron may address only portability with possibly slightly higher shrpeness between f2 to f4. And of course, faster autofocus.

 

However, going SL 50 cron would probably leave an open door for a 50 Noctilux, at least for the rendering.

Will be interesting to see optical differences between the 50 APO-M and 50 CRON-SL. Having the former, I may skip the latter, although I see advantages with AF and weather sealing.

[BernardC]

I was looking purely at the physics of the calculation (rather than perception - image size, processing, viewing distance etc). There have been excellent papers linked in other threads on DoF calculation.

 

DoF is subjective in a very important way: what is subjectively sharp enough for one image will not be sharp enough for different image.

 

Going back to the physics issue, DoF is only an absolute for a "perfect" lens with an aperture that is impracticably thin (much thinner than the wavelength of light).

In the real world, depth of field depends on the level of optical correction. A highly corrected lens (one in which red, green and blue light focus on the same flat plane), depth of field will be more shallow. Less correction means that depth of field will spread-out, but peak sharpness will be less.

Furthermore, the "spread" of depth of field varies depending on how each optical aberration is corrected. The traditional "1/3 in front, 2/3 behind" spread of sharpness is characteristic of under-corrected spherical aberration. A perfect lens would be closer to 1/2 front, 1/2 back.

 

My favourite physics book about optics is Richard Feynman's "QED: The Strange Theory of Light and Matter." Highly recommended.

Edited August 12, 2018 by BernardC

[cabe]

Advertisement (gone after registration)

My assumption is that there are two basic design philosphies for Leica lenses, the Summilux-asph and the APO Summicron, and that the SL generation will follow those two paths

 

I absolutely agree!

Summilux and Summicron have a different "character", this is the Leica philosophy

Edited August 12, 2018 by cabe

[IkarusJohn]

DoF is subjective in a very important way: what is subjectively sharp enough for one image will not be sharp enough for different image.

 

Going back to the physics issue, DoF is only an absolute for a "perfect" lens with an aperture that is impracticably thin (much thinner than the wavelength of light).

In the real world, depth of field depends on the level of optical correction. A highly corrected lens (one in which red, green and blue light focus on the same flat plane), depth of field will be more shallow. Less correction means that depth of field will spread-out, but peak sharpness will be less.

Furthermore, the "spread" of depth of field varies depending on how each optical aberration is corrected. The traditional "1/3 in front, 2/3 behind" spread of sharpness is characteristic of under-corrected spherical aberration. A perfect lens would be closer to 1/2 front, 1/2 back.

 

My favourite physics book about optics is Richard Feynman's "QED: The Strange Theory of Light and Matter." Highly recommended.

I will look that out.

 

However, the point I was making is the perception of depth of field maybe subjective, but its calculation is not - the depth of field calculators online and on my iPhone App give a figure, based on the pixel sized, focal length of the lens, aperture and focusing distance. These give a non-subjective result.

 

PS - the relevance of the point I’m making badly is that when the 50 Summilux-SL was released, some rather wild claims were made about the lens having a shallower depth of field than was possible, and similar comments have appeared in relation to the new Summicrons. If the focal length is accurately described, and the aperture similarly accurate, on the same sensor, for a given f-stop and focusing distance, there is no way the depth of field of a Summicron matches a Summilux. That’s not subjective ... perception, wishful thinking or hyperbole is somethig else.

Edited August 12, 2018 by IkarusJohn

[mmradman]

Faster lens does mean twice as fast shooting, handy for handheld shooting.

 

DOF, in practical shooting situations hardly much difference between f1.4 and f2. Any sensible photographer closes down several F stops to get some reasonable depth, exceptions seem to be bloggers for the web crowd.

[Jeff S]

John, read especially Mike Johnston’s response to Huw Morgan in the featured comments section of the above link.

 

This one... http://theonlinephotographer.typepad.com/the_online_photographer/2018/08/readers-weigh-in-on-the-olympus-25mm-ƒ12-and-the-pentax-hd-fa-50mm-f14-sdm-aw.html

 

Jeff

[IkarusJohn]

Yes, read that, Jeff.

 

There’s a slight cross purpose in what that blogger is writing about (perceived or acceptable sharpness) and what I was referring to (predictable depth of best focus).

 

The former is subjective, depending ultimately on extent of enlargement and viewing distance (and the other factors he mentions).

 

At risk of splitting hairs (call me a pettifogger if you like - it seems “lawyer” and “dentist” are terms of abuse here), but what the article refers to is not depth of field, or plane of best but acceptable sharpness. Depth of field actually remains unaffected by sensor size, print size or viewing distance. None of those affect the relationship between the out of focus areas in front of or behind the area that is “in focus ”, or if you prefer in the area of best focus, or depth of field.

 

The factors identified in the blog will affect how acceptable the in focus area is, but not depth of field.

 

In absolute terms, depth of field is absolutely determined by pixel size (or circle of confusion, if you prefer) for a given sensor, selected aperture, focal length of the lens and focusing distance. That’s the simple physics of it, as I understand it from my reading on the subject.

 

Cheers

John

[Chaemono]

It sounds plausible that there are two basic design philosophies with Leica lenses but I don’t think it’s that simple. The 75 Noctilux-M clearly follows the APO Summicron philosophy, so does the 90 Summicron-SL. The 50 Summilux-SL adheres perhaps to the Summilux-ASPH philosophy. But what about the 75 Summicron-SL? From all the pictures I’ve seen the OOF areas appear busy, not smooth like the 50 Apo Summicron produces.

[helged]

It sounds plausible that there are two basic design philosophies with Leica lenses but I don’t think it’s that simple. The 75 Noctilux-M clearly follows the APO Summicron philosophy, so does the 90 Summicron-SL. The 50 Summilux-SL adheres perhaps to the Summilux-ASPH philosophy. But what about the 75 Summicron-SL? From all the pictures I’ve seen the OOF areas appear busy, not smooth like the 50 Apo Summicron produces.

 

 

Not as far as I can see/tell...

[Chaemono]

Thanks, but here a bit busy OOF areas with the 75 Summicron-SL to my eyes. http://www.aphotovid.com/leica-apo-summicron-sl-75-f-2-asph/.

[helged]

Thanks, but here a bit busy OOF areas with the 75 Summicron-SL to my eyes. http://www.aphotovid.com/leica-apo-summicron-sl-75-f-2-asph/.

Hard to disagree, but the degree of pp will quickly influence the oof rendering, and these photos seem quite massaged to my eyes.

 

My comment was mainly to the statement that "all" 75-SL images have busy oof rendering, which I disagree about. Only controlled shooting with the two SL Crons, with similar pp, may uncover systematic oof differences. Personally, I highly value the 75-SL. And yes, the 90-SL looks very, very fine as well...

[Chaemono]

Fair point. Looking at the 75 Summicron-SL pictures, I cannot help thinking that the lens follows more the Summilux-ASPH philosophy.

[mmradman]

I thought whether background is busy or smoothed over depend very much on F stop, distance between the camera to plane of focus and background and more importantly on how "busy" the background itself is.  Those sample pictures taken in India have busy street background.  "Busyness" is more result of the picture setup than lens design itself.  Of course longer FL used in the same shooting setup will have shallower DOF.

[Chaemono]

Perfect point. We are debating lens factors that are affecting bokeh but are looking at pictures taken under different conditions. It would be good to shoot the 75 Noctilux-M and the 75 Summicron-SL side by side. Even if it may sound odd, the 75 Noctilux clearly follows the Apo 50 Summicron philosophy and from the pictures I see the 75 Summicron-SL draws like a Summilux. I don’t have the 75 Summicron but perhaps I can borrow it. It won’t be in the next couple of weeks, though.

[Chaemono]

And Peter Karbe sort of confirms it here:

 

https://www.reddotforum.com/content/2016/09/setting-a-new-standard-with-leica-sl-lenses-a-discussion-with-peter-karbe-at-photokina-2016/

 

Setting a new standard with Leica SL Lenses: A discussion with Peter Karbe at Photokina 2016

...

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.

 

Okay. Let me get this straight. You’re able to offer an f/1.4 look at f/2 and even higher resolving power?

 

Yes. 

 

[Advertisement]

Hallo,

Look here: Leica L-Mount

[sillbeers15]

The fully open aperture OOF rendering between the SL75 & SL90 isn't that pronounce except the SL90 image looks a little more compressed compared to SL75.

I've shared the post below before, just to show once more. I personally prefer the SL75 over SL90 as I hope to use it more for full body length portrait shots.

 

APO-SL75 vs APO-SL90.001 by sillbeers15

Edited August 13, 2018 by sillbeers15