2/50mm Summicron-SL

[Chaemono]

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Thanks. Are these crops? I suppose not. So, you changed your position to make the objects in focus appear equally large in the frame. Correct? Now look at the background blur of the 75. The OOF area is soft with few details. It would be good to have shots with people in the background to compare. The 75 still looks like a Summilux to me.

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[scott kirkpatrick]

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.

 

 ... perception, wishful thinking or hyperbole is somethig else.

Here's where we disagree.  The simple geometric optics formula that give such nice crisp numbers in an app make assumptions about lenses that are no longer true when there are more than a dozen elements spread over 10-15 cm, each group moving independently.  Until lens makers publish MTFs for the image plane a few percent before and behind the plane of focus, we may have to trust our lying eyes instead of 50 year old "thin lens" formulas.  I.e, perception rules, physics is over-simplified.

Edited August 14, 2018 by scott kirkpatrick

[IkarusJohn]

Here's where we disagree.  The simple geometric optics formula that give such nice crisp numbers in an app make assumptions about lenses that are no longer true when there are more than a dozen elements spread over 10-15 cm, each group moving independently.  Until lens makers publish MTFs for the image plane a few percent before and behind the plane of focus, we may have to trust our lying eyes instead of 50 year old "thin lens" formulas.  I.e, perception rules, physics is over-simplified.

 

 

I'm simple.

 

That said, I never look at MTF charts, and to be honest I guesstimate depth of field, and think little more of it.  I do try to consider Peter Karbe's recommendation to select aperture for depth of field.  I take Peter's suggestion that the Summicrons at f/2 have the depth of field of a Summilux at f/1.4 with a grain of salt - I read that statement as being more to do with fall off.

 

While I like being informed, I do suspect that we all get a little ... over enthusiastic about what are frequently unimportant technical issues.

 

I fully recognise that I need to spend more time getting an interesting subject into the right part of the frame, in focus, at the right time.  Time to get out more.

Edited August 14, 2018 by IkarusJohn

[scott kirkpatrick]

Let's do the experiment.  I'll take pictures of a scene with each of the 50 Summilux-asph M and the 50 APO Summicron-M, each wide open.  (I'm using my M10 for this.)  First at a distance of about 1 m:

 

L8003102 by scott kirkpatrick, on Flickr

L8003092 by scott kirkpatrick, on Flickr

 

and then at 4-5 m distance

 

L8003096 by scott kirkpatrick, on Flickr

L8003086 by scott kirkpatrick, on Flickr

 

In each pair, the SX appears first.  I think the areas far from the plane of focus are more blurred in the SX/1.4 pictures than in the SC/2.0 pictures, but the falloff immediately around the plane of focus is very similar.  The extra sharpness of the APO SC at the plane of focus makes the contrast with slightly OOF material a little stronger than happens with the SX.  At least I think so, and this effect seems to be what is behind Leica's claims that the new SX SLs will provide image layer separation and "3D effect" when wide open comparable to what has been seen in the past with the 1.4 lens designs.

[mmradman]

Key difference i can see in above example is slightly different field of view, is it because Summilux is more like 51.6mm and APO Summicron is true 50mm?

Summilux also shown slightly more blurring for out of focus area, it is f1.4 lens after all, but APO picture is usually crisper.  I have both and prefer APO for images it produces, only reason i kept Summilux is "you never sell Leica lens".  

 

I would hazard an opinion that in good light, at maximum aperture (maybe with slow film) it would be difficult to see significant difference between two pre-ASPH 50mm, one being Summilux and other being Summicron. Fast aperture was always means to counter slow film.  Modern APO lens provide level of correction and performance across the frame not possible in old pre-ASPH designs.