Can films detect lenses of high resolution?

Discussion in 'B&W: Film, Paper, Chemistry' started by Alan Johnson, Dec 30, 2007.

  1. Alan Johnson

    Alan Johnson Subscriber

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  2. AgX

    AgX Member

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    Alan,

    often resolutions of lenses, films, etc. are compared 1/1. Which then leads to the idea of "superfluous" resolution, with the resolution of one component exceeding the resolution of the component which one considers crucial.

    However,

    There is is that rule:
    The reciprocal of the system overall resolution is made by the sum of the reciprocals of the componnent.

    1/R(t) = 1/R(c1) + 1/R (c2)....


    That means that a lens of higher resolution can still render better results in the final image with a film of inferior resolution than a lens of `apt´ resolution would do.

    In the case you refer to, however, a film of inferior resolution cannot reveal fully the quality (concerning resolution) of a superior lens.

    To do so the film must have a resolution much higher than that lens.


    Furthermore one should be carefully with dealing with resolution as something static (in the meaning of highest possible resolution under certain extreme contrast situations); the concept of the MTF gives a better outcome.
     
    Last edited by a moderator: Dec 30, 2007
  3. Dave Miller

    Dave Miller Member

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    Alan, what sort of prime lens do you have in mind? I think you may have included an extra nought on your figures.
     
  4. Alan Johnson

    Alan Johnson Subscriber

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    Dave,

    I used resolution since most of the film data,except Kodak, is given as resolution lppm. Most lens data is as MTF.I did not find much on aerial resolution of lenses.The 300-600 lppm figures I quoted were from the section on lens resolution here:
    http://www.stockphotoonline.com/C01_NotesOnPhotography/Resolution.htm
    I wondered if others agree with this assessment,it is not often commented on.
     
  5. keithwms

    keithwms Member

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    Sometimes we think of being lens limited or film limited, and there are cases where you are one or the other, but it's more helpful to think of the whole equation, as AgX mentions.

    Anyway, at a single wavelength one might get very high MTF values from a lens, but no film has monochromatic sensitivity. You can try to make a lens super apo or try to match it to a specific film sensitivity curve... but at some point it's just an academic exercise. There are so many other things that convolve to limit your resolution, like diffraction, film flatness .... technique :wink:

    I prefer AgX's approach of thinking of the system as a whole.
     
  6. Gigabitfilm

    Gigabitfilm Member

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    Aerial resolution is, what you see life - camerashutter is opened, in the film-area you pose your microscope with minimum aperture 1 or higher and you look through to a star-like object. The astronomical people have thick books about the different diffraction rings you see from stars (or light-point-scources), depending on the quality of your calculated and sometimes self produced optical system. With the program Optalix I calculate sometimes optics. All optical programs will show the resolution or MTF-function of your calculated system.

    Visual you can see (depending on your health) more as you can detect on high resolution films up to 1000 linepairs/mm. Perhaps this is not correct, when you use high speed holofilms with around 2000 linepairs/ millimeter resolution. Once I have done it. The bad of these holofilms is: they are absolutely clear and react like a lightpipe. They have speeds around 3-6 ISO, but you must load your camera in real darkness.

    The next is - you photograph on earth terrestrical things, not stars. You need depth of focus. You need planety of field, no curvature of field as any optics will have (normal have 10xf curvature radius, very well have 40xf). Optical design is, to construct a special "caustic" form, where the ray-beams will get the smallest point. Correct calculated, the smallest point with best resolution is very sensitive in focusing, but changing the caustic form to a kind of hour glass, where the small part is very very long, you can minimize the influence of curvature of field, because in the center of the image your caustic is starting on one of the end, and on the corners of the picture, where normally unsharpness must be through curvature of filed, is just the other end of the caustic. Thats the trick optic design use. When you use this trick, you minimize a little your possible resolution.

    To the practical question: Of course it makes sense, to use a better lens for "normal" resolution films. A friend of mine bought the Zeiss ZM 1:2/50mm for his Nikon, using with normal 400 ISO films. He was astonished about the better sharpness now. Of course, never he would reach the optical values of this lens with normal 400 ISO films. But now there is more detail, even in grainy parts. And he has a lens for better films - who will know?
     
  7. Alan Johnson

    Alan Johnson Subscriber

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    Interesting the effect found with the Zeiss lens and 400 ISO film.
    I heard similar before with Leica and Delta 400, admitted with somewhat disbelief.
    Perhaps the smallest of the grains may line up to form image at low contrast,it's hard to explain.
     
  8. AgX

    AgX Member

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    That’s why I referred to the MTF.
    Think of a theorethical aero lens with an extreme max. resolution (let’s forget about the sensor), however with a mediocre contrast transfer over a wide range of resolutions. That lens could be quite useful to a skilled interpreter with his technical means, in case maximum resolution would be the main issue. For general pictorial use such a lens would be counterproductive, a common lens with much lower max. resolution but higher contrast transfer over its whole range would give more pleasant results due to its `brilliance´.


    However in that case of those new Zeiss lenses with their proclaimed high resolution, I expect that they will have a rather high overall contrast transfer too. Thus using such a lens on a film with rather low resolution could gain higher micro-contrast in those fields of the film's resolution or even below, than a lens some decades older.

    You can turn the whole thing round: Using high resolution pictorial films on motives with do not have such details which would call for the use of such films can still result in better micro-contrast than the use of some common film. (That’s why the manufacturers of such film/developer combos tend to advice them as general purpose films.
     
  9. braxus

    braxus Member

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    Up until this year, Kodak Gold 100 was probably the sharpest color neg film out there. That was versions 1 to 6. Now 7 the MTF has gone down. TMAX 100 may be one of the last very sharp films out there.
     
  10. dpurdy

    dpurdy Member

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    According to their original marketing, ACROS was the sharpest regular film available.
     
  11. Fotohuis

    Fotohuis Member

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  12. dancqu

    dancqu Member

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    Then the print paper, 100 ln/mm, and the optics of enlargement
    all taking additively their toll.

    LOW contrast DOCUMENT developer? Dan
     
  13. Fotohuis

    Fotohuis Member

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    Yes, like Rollei Low Contrast (RLC), Technidol, SPUR Technospeed, Moersch UGI, or a high Rodinal dilution (1+150 or more).
     
  14. AgX

    AgX Member

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    Comparing film resolution figures:

    We are generally looking at the highest resolution figures, those for high contrast subjects, as we are assuming that those figures corresponding to low contrast subjects will be proportional in value.
    Or in other words: comparing films with different high contrast resolution figures, we expect that the one with the highest figure will also yield the highest figure for low contrast subjects.

    I guess this will be the case for most common films. However this does not necessarily be the case, especially not with speciality films!

    Thus we should have both figures in mind.
     
  15. nworth

    nworth Subscriber

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    As pointed out early in the thread, the resolution you see in a photograph is a combination of the lens and film resolutions. With any decently high resolution film, you will continue to see improvements in the image as the lens resolution gets better, even if the lens resolution is quite far above the film resolution. That assumes all other factors are equal. There are several factors that affect resolution that make most of these discussions meaningless: resolution changes across the field of the lens; resolution is affected by film flatness and alignment of the image plane; resolution for a given lens changes with the wavelength of the light; resolution can change with temperature because of changes in the lens alignment; motion (even less than a wavelength); resolution changes depending on the location of the principal planes of focus; etc. In fact, it is just about impossible to design a lens with a reliable resolution of 500 lppmm. Very high resolution lenses are generally designed for a controlled environment at a single wavelength, with narrow fields, and at fixed focus points.
     
  16. Alan Johnson

    Alan Johnson Subscriber

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    I can appreciate the comments to the effect that lens contrast should be detectable. I found some old tests from Amateur Photographer magazine where T-max 100 developed in Acutol was used.Resolution at f 5.6 for high and low contrast targets was:
    Canon EF 50mm f 1.8 127 lppm, 80 lppm
    Zeiss Planar 50mm f 1.7 129 lppm, 92 lppm
    Evidently the film can detect the better low contrast detail from the Zeiss lens but cannot detect any difference in the high contrast detail.