Can lens or camera have a 'clinical' rendering?

Started 1 month ago | Discussions thread
57even Forum Pro • Posts: 14,724
Re: Can lens or camera have a 'clinical' rendering?

fPrime wrote:

57even wrote:

fPrime wrote:

57even wrote:

fPrime wrote:

57even wrote:

fPrime wrote:

57even wrote:

fPrime wrote:

I’ve certainly described some lenses as clinical. To me a “clinical” lens is simply one that is highly corrected for optical aberrations, distortion, vignetting, and soft corners when shot wide open. I use the term dispassionately. For some applications (like astrophotography, for example) a clinical rendering quality is actually preferable.

The downside of clinical lenses is that they tend to draw less microcontrast and 3D Pop once stopped down. That can be counterproductive to some photographic use cases.

fPrime

This doesn't make a lot of sense. Why can't a well corrected lens have good microcontrast?

It’s likely that my definition of microcontrast differs from yours.

fPrime

That doesn't answer my question.

I didn't want to sidetrack Erik's thread on clinical rendering into yet another microcontrast debate. But basically, if microcontrast is defined as simply an extension of global contrast with respect to higher spatial frequencies which yields more “bite” in the fine details of an image, then extremely well-corrected lenses will certainly deliver more of that quality.

If, however, we view microcontrast as tonal gradation, then these same, sharper, clinical lenses deliver less image microcontrast. How so? High Refractive Index glass elements differentially absorb fragile blue wavelengths over green and red wavelengths. The more elements that designers use to correct for aberrations and un-sharp corners, the more that low-gain blue wavelengths in the scene are gated out. This muddies the scene's microcontrast globally but especially so in the shadows and dark portions where low-gain blue wavelengths often dominate.

fPrime

Did you just make that up or read it on an internet site?

Unfortunately I can't take credit for the definition. Many professional photographers view microcontrast as tonal resolution including Irakly Shanidze and Mark Wieczorek and Yannick Khong who have all published articles on it. Irakly leads a fine art photography academy in Detroit. What do you lead in the photographic world in comparison?

I am not going to argue about definitions of a term, but I was referring to the pseudo scientific guff immediately following it.

Was that the "guff" that you were unable to cogently refute? Got it. Smearing it was the best you could manage.

However, I will take credit for illustrating the definition with real world image examples so that lay people such as yourself can better understand it. I've also linked the data on blue-wavelength light absorption by HRI glass to a loss of microcontrast transmission in photographic lenses.

Good for you, but it doesn't answer the question. I was asking why a lens cannot be well corrected and have good micro contrast. Using HRI glass is not a prerequisite for a well-corrected lens.

Please show us a highly corrected lens that employs no HRI glass then, haha. In lenses it's been common design practice now for decades to use higher RI optical glass wherever possible to minimize the weight and size of lenses. The reason is simple... the higher the refractive index of the glass is, the less glass it takes to bend light. HRI 1.6 optical glass was even doped with radioactive Thorium as early as 1939 in order to minimize the dispersion caused by the HRI glass.

fPrime

1.6 is not high, but it's still irrelevant. We are not very sensitive to blue so it makes relatively little difference to our perception of contrast.

You can check the relative absorption characteristics here:

https://www.edmundoptics.co.uk/knowledge-center/application-notes/optics/optical-glass/

You will see that very few have any significant reduction in blue absorption below 400 nm, about where most sensors stop recording...

https://www.dpreview.com/forums/post/61990852

Peak blue response of a sensor is about 440-460 nm, and the worst case glass compound listed above (N-SF11 RI = 1.78) has a response of 98% at that WL. In fact, the lowest response at  450 nm is NaBF10 (RI = 1.67), but it's still 95%.

So please and explain why good correction means lower micro contrast, preferably using real science and actual examples.

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"A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away." Antoine de Saint-Exupery

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