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The Definition of "Lens Contrast"


trastevere

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While I am aware of the meaning of "contrast" with respect to a black and white print or film negative (though I don't think I could define or measure it numerically), I am not confident of the word's exact meaning with regard to lenses. Is it simply a lens's propensity to produce (and here I'm showing my age) a contrasty b+w film negative? Of course I don't even understand what is meant by a contrasty color image either, not really.

Thanks.

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While I am aware of the meaning of "contrast" with respect to a black and white print or film negative (though I don't think I could define or measure it numerically), I am not confident of the word's exact meaning with regard to lenses. Is it simply a lens's propensity to produce (and here I'm showing my age) a contrasty b+w film negative? Of course I don't even understand what is meant by a contrasty color image either, not really.

Thanks.

 

If you have a digital Leica and some lenses of very different age is quite simple to understand the concept by direct experience : take a picture of a scene with a good variety of colors, in bright sun (but at an hour so that you have not STRONG direct lighting): one , say, with a modern 90 like Summarit or Elmarit M , the other with a prewar Elmar 90 (the cheapest old classic to buy... same can be made with a modern Summicron or Summarit 50 and a Summitar or Xenon 50) , develop both in LR or other Raw developer with the same settings and LOOK at the colors... then play with the contrast slider on the image from the ancient lens : you WILL NOT be able to achieve the same color aspect of the image taken with the new lens , and THIS is the consequence of the different contrast of the two lenses; making this with a Gretag color checker and measuring the color values with proper tools can be more scientific, but less easy and less immediate to understand: a big monitor to see the images side by side is the only need.

Edited by luigi bertolotti
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Lens contrast is not the overall contrast that it renders of the scene but the micro contrast between details. This is increased by better lens coating, design, and the glass chosen, and unfortunately it is also often confused with lens sharpness. Essentially it is shown in the different design philosophies of Leica and Zeiss, where Leica goes for a more gentle and smooth tonal transition in micro detail, more accurate in my eye, and Zeiss go for a harder edge, giving the image lots of 'punch'.

 

Overall contrast is also a result of similar coating, design, and glass considerations, but is also factored in are the contrast of the scene, the film/digital settings, the light, the photographer, the processing, and the post processing. So it can't be looked at as being about 'lens contrast', there are too many other considerations although as any photographer will know who has a selection of old and modern lenses it is possible to use an older lens to reduce overall contrast, but at the same time it is also likely to change other factors within the image, such as colour contrast (not the same as tonal contrast). And there is also to consider the ratio where micro contrast is increased or reduced by the overall contrast, such as in a very flat or contrasty scene, or a lens with a damaged coating.

 

So given all the variables that can affect overall contrast it becomes meaningless ascribing the overall scene to 'lens contrast', that only affects a small aspect of the image. Which leaves the only realistic way to talk about lens contrast as the micro contrast, the detail edges, something the lens demonstrates day in day out and where one lens has inherently more or less than another.

 

Steve

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I always scratched my head when people said they prefered older less-contrasty lenses in contrasty lighting, because it seemed to me exactly the opposite. I learned "contrasty lens" to mean one which could differentiate a wider range of subject contrast.

 

 

Me too... and my opinion is that it is true that the output from an old lens of s strongly contrasted scene can be more pleasant, but is also true that the output from a modern "contrasty" can be mitigated in developing.... at the end, as always, one can modify a natively "rich" information, but cannot "create" an information that is missing from the original source... The real truth is that we Leica lovers do like a lot to use our old gear... ;):)

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I learned "contrasty lens" to mean one which could differentiate a wider range of subject contrast.

Exactly. A 'contrasty' lens will differentiate tonality better, especially in the shadows. A low contrast lens will lose shadow differentiation due to veiling flare.

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Exactly. A 'contrasty' lens will differentiate tonality better, especially in the shadows. A low contrast lens will lose shadow differentiation due to veiling flare.

 

It does seem unfortunate that we use the same word when talking about prints, where in a high contrast print the various tones in the middle might be lost, and so, not "differentiated."

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It does seem unfortunate that we use the same word when talking about prints, where in a high contrast print the various tones in the middle might be lost, and so, not "differentiated."

I suppose that we could go all technical for lenses and discuss MTF % - but I think not:D.

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:-) I have never been concerned about lens contrast myself but it is mentioned often and is a thing that I know I don't completely understand/appreciate. In fact it sounds like it is less relevant in B+W. Luminous Landscape, I see, refers to a certain book by Canon where this is discussed. Thanks for your responses.

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