Thoughts about lens resolution.

[the scanner-guy]

Hi, today while testing the Scanner-camera I tried to mount an enlarger lens: a Schneider Componon 150mm f/5.6.
Is not the Componon S, but the older version, with the chrome barrel: I know is a good lens for its times, but certainly not as good as the newer version, and of course very far from the new digital-technical lenses from Rodenstock and Schneider.
The dot-pitch of the scanner-camera is about 4 micron, and the scanned portion of 40x40mm (because of the adapter) gives a 90MP full RGB 48-bit image.

Now, with that being said, I want you to look at this picture in full-resolution:



The lens was set to f/9: I wanted to use f/11 (the sweet spot of this lens) but it was too dark(the camera doesn't have an adjustable shutter), so I sharpened the image a bit, at 0,9 pixel range but only in medium tones (using the smart sharpener in CS5).

This makes me thinking: why medium-format-digital users are always complaining about the resolution of the lens(not always but you get the point) when talking about the sharpness on their pictures? Why they buy 4-6000$ lenses when an 80$ used lens can do a very good job at 4 micron?

 

[the scanner-guy]

I see no anwers, but I have another question.
Why those digital lenses are considered "high resolution" even if they need to be stopped down from f8 to f16 to have the maximum performances?
If using the best lenses, limited only by diffraction, let's say at f11, gives me a maximum calculated resolution of 30-40 MP in a medium format sensor, why I am seeing a clear 90 MP image in less space than medium format, and I am not even using one of those lenses?

 

[Leigh]

They're "high resolution" because they can charge more money by saying that.

Since there's no industry-standard definition of that term, it's meaningless.

All lenses need to be stopped down a couple of stops for optimum performance.

- Leigh

 

[baudolino]

My experience is that all the MF lenses that I have used with my digital back (Zeiss lenses for Contax 645 and Schneider lenses for the Hy6) are very sharp, and very likely outresolve the 33MP sensor. Any issues that I have had with lack of sharpness in my images have been because of me not being sufficiently meticulous with shutter speed or focusing. It took me a while to realize that (a) when hand-holding, I really need to shoot at least at 1/250s (with an 80mm lens) to reliably achieve critical sharpness and (b) the DOF is so shallow that very small deviations from optimal focus make the image less than optimally sharp. It only takes to take a few well focused shots under strobe lighting to realize how razor sharp these MF lenses really are.

 

[fotografz]

So, the premiss is that all lenses are equal? Really?

First of all, not everyone shoots at f/11. Many lenses are optimal at f/5.6 or 8 ... not f/11.

I sure see a big difference in non digital type view lenses compared to the newer type.

I absolutely see a difference in the newer reflex lenses for MFD cameras if sharpness and contrast are the criteria.

Not sure what is being proposed here.

-Marc

 

[Leigh]

I sure see a big difference in non digital type view lenses compared to the newer type.

Hi Marc,

Don't confuse general advances in lens technology with contemporary camera technologies. Advanced lens design software coupled with modern computer-controlled manufacturing equipment enable us to produce lenses that were only dreamt of a few decades ago.

Yes, modern lenses are vastly superior to those of the early 20th century, but it's not specifically due to the advent of digital cameras. That connection is more marketing hype and price justification than reality.

- Leigh

 

[fotografz]

Hi Marc,

Don't confuse general advances in lens technology with contemporary camera technologies. Advanced lens design software coupled with modern computer-controlled manufacturing equipment enable us to produce lenses that were only dreamt of a few decades ago.

Yes, modern lenses are vastly superior to those of the early 20th century, but it's not specifically due to the advent of digital cameras. That connection is more marketing hype and price justification than reality.

- Leigh

Understood ... and I wasn't confusing them actually ... I think the prevailing premiss is that some of these digital backs are less forgiving, and the files tend to be viewed at incredibly high magnifications even if the actual use and viewing doesn't require that kind of scrutiny.

 

[Leigh]

I think the prevailing premiss is that some of these digital backs are less forgiving, and the files tend to be viewed at incredibly high magnifications even if the actual use and viewing doesn't require that kind of scrutiny.

True.

One potentially important distinction is the difference in the thickness of the "emulsion" with digital sensors v. film. It's my understanding that the digital sensor is essentially flat, thus limiting the achievable depth of focus (not depth of field).

With film, if the image is focused anywhere within the emulsion thickness, it will be perceived as "in focus". Of course at other depths the silver grains may be exposed, but the resulting image is blurred. This is why high-resolution films like Tech Pan had very thin emulsions.

- Leigh

 

[the scanner-guy]

So, the premiss is that all lenses are equal? Really?

Absolutely not!

First of all, not everyone shoots at f/11. Many lenses are optimal at f/5.6 or 8 ... not f/11.

Ok. I need the name of those lenses with the sweet spot at f/5.6
It's not a provocation. I really need a lens like that.

I sure see a big difference in non digital type view lenses compared to the newer type.
I absolutely see a difference in the newer reflex lenses for MFD cameras if sharpness and contrast are the criteria.
Not sure what is being proposed here.
-Marc

In what terms you "see" the differences? looking at technical data, or maybe looking at sample pictures, or personal experience?

I'm not proposing anything: I'm in the middle of choosing a lens to archieve the optimal resolution for the camera that I'm building, and the technical data of most of the "top" lenses makes me thinking.
I need a lens that can resolve 4 microns. I don't care if it's medium format, or large, or small format(because even in 30x30mm I can shoot 60+ MP images), so I can't use lenses with f8-f11 sweet spot: I need something between f2,8 and f4.

On the other hand, I used two lenses on this camera, both old (beta variogon 75-150 and Schneider Componon 150mm) and with a sweet spot, as expected, between f8 and f11. but looking at the images (142MP full frame, and 90MP the crop I posted here) I'm surprised that are not that blurry at all at 100% magnification...

To make a long story short: when searching for the maximum resolution, why should I choose some extremely expensive lenses, when they are limited by diffraction at less resolution than the sensor, and at the same time I can archieve the same limited (but really good at the eye) resolution using an older lens?