Lindolfi Posted March 18, 2012 Share #1 Posted March 18, 2012 Advertisement (gone after registration) Contrast versus Resolution? One could wonder if (modern) Leica lenses would be optimized for contrast, if that would compromise resolution. To show that a good lens can satisfy both, the following experiment has been done with a Summilux 50/1.4 ASPH at f/1.4. The lens was mounted on an M6 of which the backdoor was opened and the shutter fixed to open. At a distance of 10 meter a resolution test chart was mounted on a wall and the image produced by the Summilux was photographed with a Leitz Photar 12.5/2.4 at f/2.4 with a bellows extension of 220 mm. This creates an enlargement of the image plane of the Summilux of 17 times in the final image of the capturing camera. Below the result: The Summilux reaches a resolution of at least 500 linepairs per mm. at f/1.4, which is 6.5 times more than the M9 sensor can resolve. Although this study has little relevance for photography with an M9, it does show that a very contrasty Leica lens like the Summilux 50/1.4 asph can have very high resolution, even at its full opening. Link to post Share on other sites More sharing options...
Advertisement Posted March 18, 2012 Posted March 18, 2012 Hi Lindolfi, Take a look here Contrast versus Resolution?. I'm sure you'll find what you were looking for!
jaapv Posted March 18, 2012 Share #2 Posted March 18, 2012 According to Erwin Puts it is incorrect to assume contrast and resolution are opposing parameters. In general the lens with more resolution will exhibit more contrast. Link to post Share on other sites More sharing options...
Guest #12 Posted March 18, 2012 Share #3 Posted March 18, 2012 Which chart is that; is that the one you've posted before? Thanks Link to post Share on other sites More sharing options...
pico Posted March 18, 2012 Share #4 Posted March 18, 2012 I don't mean to quibble, but the color of the target might be diminishing the potential resolution due to its long wave. Link to post Share on other sites More sharing options...
Lindolfi Posted March 18, 2012 Author Share #5 Posted March 18, 2012 According to Erwin Puts it is incorrect to assume contrast and resolution are opposing parameters. In general the lens with more resolution will exhibit more contrast. According to Leslie Stroebel (View Camera Technique, Focal Press, page 116, figure 5-40), they are not necessarily couple, see here. A, B and C are different lenses with different design. Which chart is that; is that the one you've posted before? Thanks Yes, it is a chart I bought in a great camera shop in Prague. There is no brandname on it. I don't mean to quibble, but the color of the target might be diminishing the potential resolution due to its long wave. In principle you are right that long wavelengths reduce resolution. Thanks. But this was illuminated by a halogen lamp with lots of medium wavelength in it and the diffraction limit at f/1.4 is 1065 linepairs per mm (Rayleigh criterium) for green. The statement from my measurement is that the Summilux 50/1.4 asph resolves at least 500 linepairs per mm and that is still valid. Link to post Share on other sites More sharing options...
Double Negative Posted March 20, 2012 Share #6 Posted March 20, 2012 I've shot targets with my Summilux as well for a review, but I can say quite safely just by taking pictures with it - it's an amazing lens regardless of adjectives. It's sharp, contrasty, has a high resolution, etc. They're all in there. Link to post Share on other sites More sharing options...
Michael Geschlecht Posted March 21, 2012 Share #7 Posted March 21, 2012 Advertisement (gone after registration) Hello Everybody, In lens design contrast & resolution are 2 of the variables which have an inversely related relationship. A lens w/ a larger F stop will resolve more information than the same lens w/ a smaller F stop all else being equal. A lens w/ a smaller F stop will exhibit a higher degree of contrast than the same lens w/ a larger F stop all else being equal. Along w/ compensating for other abberations a designer will reduce the maximum F stop (resolution) of a lens to the point where the resultant increasing contrast combined w/ the remaining resolution produces the best balance of image. Best Regards, Michael Link to post Share on other sites More sharing options...
Lindolfi Posted March 21, 2012 Author Share #8 Posted March 21, 2012 Michael, you are equating F-stop with resolution: the larger the opening, the higher the resolution, you state. That is true if the lens is diffraction limited at its widest aperture. For a perfect lens, the physics of the opening determines the resolution because of the, not the optics. But if the lens is perfect, there are no other aberrations and therefore contrast is also high. In the real world contrast and resolution are not necessarily coupled. "contrast" refers to high modulation at the medium and lower frequencies, while "resolution" is to have at least some modulation at the very high spatial frequencies. Link to post Share on other sites More sharing options...
giordano Posted March 21, 2012 Share #9 Posted March 21, 2012 In the real world contrast and resolution are not necessarily coupled. "contrast" refers to high modulation at the medium and lower frequencies, while "resolution" is to have at least some modulation at the very high spatial frequencies. I'm waiting for a certain party to complain that the word "modulation" can only properly be used of radio signals. Link to post Share on other sites More sharing options...
250swb Posted March 21, 2012 Share #10 Posted March 21, 2012 I'm waiting for a certain party to complain that the word "modulation" can only properly be used of radio signals. Very funny Steve Link to post Share on other sites More sharing options...
Guest Ornello Posted March 21, 2012 Share #11 Posted March 21, 2012 I'm waiting for a certain party to complain that the word "modulation" can only properly be used of radio signals. Nope. It's OK in this context. Erwin Puts has written a great deal of detailed information on this topic. Suffice it to say that there is more to it than meets the eye, and that Leitz has made very crafty decisions in lens design over the decades, favoring simpler designs with higher-index glasses that have fewer elements and elements with gentler curves. Early on, design compromises were necessary that could be simplistically reduced to 'contrast vs resolution' (more elements reduced contrast but allowed more corrections), but it is more complex than that. Even with the latest glasses and anti-reflection coatings, compromises still are necessary, but they are very much less crude. Here is some discussion of these matters, but there is more: http://www.imx.nl/photo/optics/optics/page93.html Here is a hint: "After 1960 new glasses with high refractive indices became available. The classical glass catalogue was filled with what we now call the “old glass types”, essentially developed by Ernst Abbe. As these glasses had low refractive indices, one had to bend the lens elements quite strongly to get the type of correction needed. But such curved glass is sensitive to manufacturing tolerances and one could not accomplish all. So the search for new glasses started with the additions of rare earth elements." Link to post Share on other sites More sharing options...
mjh Posted March 21, 2012 Share #12 Posted March 21, 2012 In the real world contrast and resolution are not necessarily coupled. "contrast" refers to high modulation at the medium and lower frequencies, while "resolution" is to have at least some modulation at the very high spatial frequencies. I was already wondering what ‘contrast versus resolution’ was supposed to mean, given that the resolution of a lens is commonly measured and expressed as the contrast delivered at certain spatial frequencies. So what you really referred to was ‘contrast at low and medium spatial frequencies versus contrast at high spatial frequencies’. And yes, quite obviously you can have both. Link to post Share on other sites More sharing options...
stunsworth Posted March 21, 2012 Share #13 Posted March 21, 2012 Nope. It's OK in this context Michael, he wasn't being serious. It was a joke at your expense. Link to post Share on other sites More sharing options...
bill Posted March 21, 2012 Share #14 Posted March 21, 2012 Nope. It's OK in this context. As you were, chaps. Swiss Toni has granted approval. Regards, Bill Link to post Share on other sites More sharing options...
Guest Ornello Posted March 21, 2012 Share #15 Posted March 21, 2012 As you were, chaps. Swiss Toni has granted approval. Regards, Bill This is enlightening: http://www.imx.nl/photo/leica/lenses/lenses/page82.html Link to post Share on other sites More sharing options...
bill Posted March 21, 2012 Share #16 Posted March 21, 2012 No, it's Puts. It's about as enlightening as a shot of Nytol. Have you tried the POST REPLY button? So much easier on the servers and the eye than constantly quoting the post immediately above... Regards, Bill Link to post Share on other sites More sharing options...
Guest Ornello Posted March 21, 2012 Share #17 Posted March 21, 2012 No, it's Puts. It's about as enlightening as a shot of Nytol. Have you tried the POST REPLY button? So much easier on the servers and the eye than constantly quoting the post immediately above... Regards, Bill I am replying to a specific post there. If the post I am replying to is long, I will trim it. Link to post Share on other sites More sharing options...
Lindolfi Posted March 21, 2012 Author Share #18 Posted March 21, 2012 And yes, quite obviously you can have both. Yes and you can have one or the other or neither. Link to post Share on other sites More sharing options...
Guest Ornello Posted March 21, 2012 Share #19 Posted March 21, 2012 Yes and you can have one or the other or neither. Depends on how much you pay....better lenses cost more...and so does rehearsing! Link to post Share on other sites More sharing options...
tobey bilek Posted March 21, 2012 Share #20 Posted March 21, 2012 Nope. It's OK in this context. Erwin Puts has written a great deal of detailed information on this topic. Suffice it to say that there is more to it than meets the eye, and that Leitz has made very crafty decisions in lens design over the decades, favoring simpler designs with higher-index glasses that have fewer elements and elements with gentler curves. Early on, design compromises were necessary that could be simplistically reduced to 'contrast vs resolution' (more elements reduced contrast but allowed more corrections), but it is more complex than that. Even with the latest glasses and anti-reflection coatings, compromises still are necessary, but they are very much less crude. Here is some discussion of these matters, but there is more: DesignerGeneration Here is a hint: "After 1960 new glasses with high refractive indices became available. The classical glass catalogue was filled with what we now call the “old glass types”, essentially developed by Ernst Abbe. As these glasses had low refractive indices, one had to bend the lens elements quite strongly to get the type of correction needed. But such curved glass is sensitive to manufacturing tolerances and one could not accomplish all. So the search for new glasses started with the additions of rare earth elements." Leica glass lab which was closed round 1995, developed special glasses that made possible the 1.0 Noct and 75 1.4. The Leica rep showed me a 1" cube of that stuff that was a reject. It weighed like it was solid lead. The european EPA later deemed lead could not be used in glass, so substitutes had to be found. Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.