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Micro-contrast - What is it?


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#1 bhu

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Posted 15 September 2017 - 02:03 PM

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After following an article Patrick linked, I wondered what the community understood the term micro-contrast meant. MTF was mentioned once in the article and not well explained so I thought the Fuji-x-forum would be a good place to discuss the relationship between micro-contrast and MTF. It is an important measure of glass quality, polishing, coating, and lens design.

 

Please share your thoughts on micro-contrast.



#2 9.V.III

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Posted 23 September 2017 - 09:23 AM

MTF charts measure the frequency of bright and dark contrast, but not the total light transmission, or the color tone.
The prime example I have is my Canon 400f5.6 and Samyang 800f11 lenses, they produce effectively the same amount of detail when cropped to the same field of view, but the Canon lens has much better color.
Along with that the F-stop of a lens is not a measurement of the amount of light actually hitting the sensor, thus the T-stop value that Cinema lenses always use.

From what I’ve read, when people talk about “Micro-Contrast” they’re really just saying “Color Saturation”, and total light transmission (T-stop) is probably a good indicator of how much a lens is going to interfere with colors.
Glass will always absorb some light so the better a lens is at transmitting light the less likely it is to absorb your colors.

It’s really weird that more people don’t pay attention to these things, but I guess it’s hard to keep that sort of thing in the mainstream audience with all the people out there trying talking about it are trying to get converts to a channel more than informed and educated consumers.

#3 BobJ

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Posted 23 September 2017 - 06:34 PM

Micro contrast has nothing to do with colour. A lens with high micro contrast can distinguish between increasingly small variations of tone at high frequencies. It is about resolution, which is not the same as sharpness. An image can look sharp but have low resolution. All lenses are optical compromises. A lens with high macro contrast and low micro contrast can appear sharp despite not being able to resolve fine detail. A lens built for high micro contrast can show fine detail but can produce dull and lifeless looking images. In practise a lens designer has to balance these two qualities together with many other lens characteristics. Leica and Minolta, who worked closely together for a while in the pre-af era, made low macro contrast lenses that could resolve fine detail and had a lovely subtle tonal reproduction. What the designers did was to boost the MTF figures at finer than 60 cycles at the expense of the 10-30 cycle range. A decade ago David Kilpatrick wrote a very illuminating article called "Historical Perspective on Minolta Lens Design Philosophy". I have a hard copy of this but I don't know if it can still be found online. In it he discusses some of this together with coating decisions made to help give contrast and colour consistency (lens colour was much more important in film days for obvious reasons).

 

Nowadays with exotic glasses, aspherical elements and design methods that were not available in the 70s and 80s, lenses can be made with less compromise but differences are still there. A couple of years ago I was lucky enough to attend a factory tour at Cooke optics in Leicester. Their hand built lenses are used for many feature films and TV dramas and are famed for the "Cooke Look". It's difficult to explain but involves smooth tonal transitions and beautiful bokeh. Interestingly they told me that they are able to design for the look in the design software. If you have to ask how much they cost you can't afford one! The TV companies mostly hire them. The feature film people have such big budgets that they are not a significant cost to them. Have a look at their website, it's quite interesting. www.cookeoptics.com


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#4 konzy

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Posted 11 October 2017 - 01:35 PM

Really good article with examples, about MTF charts and microcontrasts: https://photographyl...read-mtf-charts



#5 bhu

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Posted 26 October 2017 - 01:31 PM

Thanks for the link to the article, Konzy. It does a good job explaining how camera makers express lens quality to photographers.




 
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