Narrowest depth of field?

[michaelwj]

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You could also ask what's the sense of the original question

I think it's called "chewing the fat"

[michaelwj]

So Andy, are you saying I should get a Noctilux and an APO Teylt?

[Steve Spencer]

As someone who usually likes as much depth of field as possible this is a strange question: which of the Leica M lenses has the narrowest depth of field at maximum aperture?

 

For example, I know that the depth of field of the f/3.4, 135mm APO-Telyt is considerably narrower than the f/0.95, 50mm Noctilux, so I am guessing the winner (loser?) is the APO-Telyt?

 

To answer the question we have to know if you are going to keep subject distance or framing constant and you get very different answers depending on which you do. If you keep framing constant then the 50 Noctilux f/.95 has the shallowest depth of field. If you keep subject distance constant then the 135 f/2.8 has the shallowest depth of field. If you keep subject distance constant, however, you should remember you will get very different pictures using a 135 compared to a 50.

[Steve Spencer]

I might also add that in my view, although the 135 f/3.4 APO telyt is a very good lens, it does not have very good shallow depth of field capabilities and that is largely because of its long minimum focus distance and relatively slow aperture. I would often want to use it closer than 1.5M and even if I wanted to shoot it at 2M I would often want a faster aperture. This combination of long minimum focus distance (which prevents tighter framing in some cases that would allow shallower depth of field) and relatively slow max aperture (which limits how much you can open the aperture to allow shallower depth of field with looser framing) limits its use as a portrait lens when I want shallow depth of field. It just simply isn't a good shallow depth of field lens for many of my uses because of these limitations. That does not mean it isn't a good lens. It is an excellent lens for many purposes, but I think it is worth knowing its limitations and we should realize that because of its long minimum focus distance and relatively slow max aperture it won't be able to produce that shallow of depth of field in some situations and those situations include the way many people (me for sure) would like to shoot portraits.

[pico]

Regardless of the arithmetic, acutance contributes to apparent depth-of-field (or lack of it). A crisp, well defined subject of adequate contrast will usually have a more remarkable shallow look. Background appearance contributes as well. A photo where the main subject has OOF of brush, trees, buildings will enhance the effect, while a clear sky or seamless background will evince little. Close-up subjects, for example a 3/4 view head shot with one eye in focus also emphasizes lack of DOF.

 

In my modest experience my Canon 50m f/0.95 has mushy separation while the 75mm Summilux at f/1.4 has crisp separation (given proportionately equal  magnification).

 

At the moment I'm nowhere near photos to show. That would be better, of course.

[adan]

Thank you for your well reasoned response, apart from this last comment. The truth is, what do you know about my artistic intentions or the source of the question (...cropping...)?

 

Apologies - I was using the generic "you". Translate it as "If one has not yet figured out whether one.....etc."

[105012]

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Thanks everyone for your thoughts, I should have added that I was interested in constant perspective (I can shoot this with a shorter, faster lens and crop, or a longer slower lens). Of course, this is arithmetic in the end, but I asked the question because often on this forum people come out with very interesting 'side thoughts' as well as very well thought out responses (Andy, you are one of the highlights of the forum in this regard).