microcontrast and lenses

Started 3 months ago | Discussions thread
tjuster1 Senior Member • Posts: 2,198
Re: microcontrast and lenses
1

glassoholic wrote:

tjuster1 wrote:

glassoholic wrote:

Micro contrast cannot be measured in terms of resolution. It is perceptible, not measurable.

I'm not sure I buy this. Anything that is perceptible should be measurable. Perhaps the ideal method of measuring it hasn't been invented yet, but your eye's perception is based on perceiving something, so clearly that something should be definable and thus measurable.

From Roger Cicala of Lensrentals:

"I think terminology is always a problem in discussions like these. Separating sharpness into acutance and contrast is a good first step. Micro-contrast is a term that I always ask people to define when they start using it. Some consider microcontrast to be the same as resolution - how fine of a detail can the system resolve. Others (trying to explain it in words is difficult) are considering it how contrasty a given fine detail is. I tend to like the latter definition, just because, well, we already have resolution.

As to 3-D pop being snake oil, no, I don't think so. On the other hand it may be difficult to measure numerically, and unless everyone agreed on what they mean by 'microcontrast' there's no way to measure it at all."

He knows a lot more about this stuff than I do.

I also used to say microcontrast was high definition and contrast of small detail until I also realised that is, well, resolution.

Towards the bottom here, cba_melbourne references a wonderful paper from Zeiss that I read over and over many years ago. Zeiss says that MTF graphs are a very good indicator of what a lens will achieve, but also that there are many other factors that MTF charts don't show. Buy they also talk about the "steps" different lenses can have in rendering from a pure white to a pure black hard lined subject (lines used to measure MTF). However they seem to rely on the MTF graphs as the "overall" indicator of a lenses ability, and that microcontrast is a combination of resolving fine detail with a high contrast. That's fine by me, as it is a word that can have different meanings, and as Roger says, it depends on what the person bringing it up means. Maybe words like "smooth", "rough", "veiled" or "artifacts after sharpening" can be better used to describe the rendering of a lens. There is also the issue of what size is the image examined at, what distance is the image viewed at, and what is the subject matter. Not much we photograph consists of nothing but black and white lines. We take pictures of natural three dimensional objects, soft edged and hard edged... lithography lenses copy flat 2D detail.

I am the first to use MTF charts to get an "idea" of what to expect from a lens... But I have often been proven wrong. Hence the subjectivity and "inability to measure" aspects.

But the reason he says it can't be measured is because no one agrees on what it means, not because it possesses some magical quality that defies measurement. if we can all agree on what microcontrast is we should be able to design a test to see how much of it exists.

If you're going to make an argument based on microcontrast then it seems you should specify what you mean by the term. The OP defined it in a way that i would call resolution, as distinct from contrast.

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