Lens register chart

Discussion in '35mm Cameras' started by Stephen H. Westin, Oct 25, 2004.

  1. Stephen H. Westin, Oct 25, 2004
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  2. westin* (Stephen H. Westin) wrote in

    Do you have any data for the Asahiflex M37 screw mount?

    Roland Karlsson, Oct 25, 2004
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  3. No. Do you? If so, I'll add it.
    Stephen H. Westin, Oct 25, 2004
  4. Stephen H. Westin

    Jim Guest

    While you are doing that, add the Nikon Rangefinder mount.
    Jim, Oct 26, 2004
  5. Which I don't know. As I recall, it was based on the Contax mount, but
    used a different ratio on the rangefinder cam.
    Stephen H. Westin, Oct 26, 2004
  6. Stephen H. Westin

    Magnus W Guest

    westin* (Stephen H. Westin) wrote in
    Very nice!

    However, this brings up a previous question I've haed. The Minolta AF mount
    is listed in different literature to have 44.7, 44.6, or 44.5mm register.
    When discussing this with others, people have suggested that it may be
    flange-to-emulsion distance vs. flange-to-film surface distance. But this
    seems strange. I would have thought that film cannot be taken into account,
    as film thickness varies, and the distance would thus be flange-to-pressure
    plate (without film loaded). Any thoughts on this? :)
    Magnus W, Oct 27, 2004
  7. Only the notation on the Pentax mounts, which states, "45.46mm ... add
    film thickness, and get 45.50mm..." I think 0.1mm is probably too
    thick for most films, let alone 0.2.

    Does anyone have a Minolta and a good way to measure? Schneider lists
    it as 44.5mm:
    <http://www.schneideroptics.com/photography/pc-super-angulon/>. But
    then, they have the Pentax at a round 45.5. And the Rollei mount
    disagrees with Willem-Jan's list at 44.5 rather than 44.6.

    Like you, I would think that flange-to-film-rails would be the
    relevant distance, as that's what is actually part of the camera. We
    would hope that the front surface of the emulsion would be pretty
    close to that, though of course it won't be perfectly flat.
    Stephen H. Westin, Oct 27, 2004
  8. Stephen H. Westin

    Magnus W Guest

    westin* (Stephen H. Westin) wrote in
    I have lots of Minoltas, but no measuring equipment ;-) However, the old
    Minolta 9000 manual lists it as 44.6:
    Exactly. So who can answer this with any authority? I wouldn't expect
    marketing droids to know the answer -- they probably have worse sources
    than we do ;-)
    Magnus W, Oct 27, 2004
  9. Well, a page at
    <www.mir.com.my/rb/photography/hardwares/classics/minoltaxd711/> gives
    the distance as "43.7mm (+0.02 -0) measured from lens-mounting ring to
    pressure-plate rails." Anything that detailed has to be authoritative,
    doesn't it? :) But that would put the rest of the world off by
    0.8-1.0mm. Schneider, who sells their PC Super Angulon for a variety
    of mounts, lists Minolta at 43.5. Could be that Schneider measures to
    the film rails, rather than to the pressure plate.

    BTW: I found an anal-retentive answer for Leicas at
    <http://dantestella.com/technical/flange.html>. A general look on the
    Web suggests that astronomers are into this subject, but I wonder how
    exact they have to be.
    Stephen H. Westin, Oct 27, 2004
  10. Stephen H. Westin

    Bob Monaghan Guest

    * Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
    ********************Standard Disclaimers Apply*************************
    Bob Monaghan, Oct 27, 2004
  11. Stephen H. Westin

    Bob Monaghan Guest

    ooops! sorry about glitch - anyway, my point is that film varies a lot,
    see http://medfmt.8k.com/mf/flat.html postings, viz.:

    quoting Tom Christiansen:
    Print film:

    Fuji NPC: 122um
    Fuji NPH: 122um

    Slide film:

    Agfa RSX II 100: 120umB Fuji Sensia II 100: 127um
    Fuji Sensia II 400: 127um
    Fuji Provia 100F [RDP III]: 127um
    Fuji Velvia RVP: 127um
    Note: um = 10e-6 m. 120um = 0.120mm

    and from same URL, an Austin Franklin posting, viz.:
    Here are some film thickness measurements:

    Tri-X 0.135mm
    Delta 100 0.135mm
    160NC 0.150mm
    Supra 100 0.150mm
    Plus-X 0.150mm

    These measurements show the film may have as much as 0.040mm 'play'
    between the pressure plate and the inner rails.

    the point being that film does vary a lot, between and within brands, in
    thickness. Most of these offsets and errors are covered up by depth of
    focus at higher stops etc. A number of the russian rangefinders look to
    have been individually tuned to specific lenses, explaining some of the
    range of results reported when using them on other "identical" mount
    cameras ;-)

    Probably the best source would be one of the camera repair techs with
    access to tech manuals, should have this spec. for each of the camera
    brand mounts. That's the source for some of the earlier (1990s) camera
    register distance lists (text files). But comparing multiple lists would
    at least flag those that need to be researched better? ;-)

    regards bobm
    Bob Monaghan, Oct 27, 2004
  12. Oh, it's much worse than that. The Leica-oriented site I mentioned
    talks about how the film settles with time, so that if you just wound
    the camera, you get a slightly different lens-to-film distance than if
    it has been sitting for a while. Which, of course, brings up the issue
    of film flatness in general. So Pentax, say, quoting a register of
    45.46mm to allow for 0.04mm of film (or emulsion) thickness seems a
    bit optimistic.
    Stephen H. Westin, Oct 28, 2004
  13. Stephen H. Westin

    me Guest

    Excuse me please but how much pressure does it take to flatten out film?
    This statement about "settles with time" implies that the pressure plate is
    unable to hold the film flat. I have some negative film right here in my
    hand and it doesn't seem stiff enough to resist being held flat by the
    pressure plate IMHO.
    It's been a while since I pulled unexposed film out of a canister (don't ask
    me why I did) but IIRC it looked flat to me.
    Apologies if I intruded.
    me, Oct 28, 2004
  14. And Kodak Technical Pan was roughly 2/3 the thickness of Tri-X Pan.

    Michael A. Covington, Oct 28, 2004
  15. Oh, it's much worse than that. The Leica-oriented site I mentioned
    Film non-flatness is quite noticeable when I do astrophotography with sharp,
    fast lenses such as the Nikon 180/2.8. If the film has not been advanced
    for a while, then the next frame, waiting to advance, will have been partly
    flat and partly curled. It will sometimes have a detectable "hump" in the
    middle when the picture is taken. I get the best film flatness by advancing
    two frames at the beginning of a session, so that I'm always using film that
    has been curled up the whole time, rather than just half of it curled up. I
    do not know how much settling occurs over a period of minutes or hours if
    you advance the film and then don't take the picture.

    I'm photographing stars, which are point sources, and I detect focusing
    errors that would not be perceptible on an ordinary photograph.

    BTW, this is with very good camera bodies such as a Nikon F3. I presume
    that Nikon's pressure plate is properly designed and is doing as good a job
    as it can.

    Clear skies,

    Michael A. Covington
    Author, Astrophotography for the Amateur
    Michael A. Covington, Oct 28, 2004
  16. Well, if it were squeezed between two flat surfaces, perhaps not that
    much. But one side is virtually unsupported, as we have to leave a
    big hole to let the light in. And pressure is, of course, limited by
    the issues of winding effort and trying not to scratch the film. The
    Contax RTS III uses vacuum to flatten the film against the pressure
    plate before each exposure, for just this reason.
    We're talking about distances on the order of 0.01mm here, or 10
    micrometers. I don't think your eyes are quite good enough to detect
    that small a deformation. How much of a difference it makes in the
    image is a different question, and the Kyocera/Contax folks seem to
    care. On the other hand, 35mm cameras have lived with the issue for
    almost seven decades now, delivering some pretty sharp pictures. Which
    was kinda my point; how important is it to specify (and hold) lens
    register to within 0.01mm when the film thickness and flatness clearly
    vary by more than that?

    I suppose I shouldn't mention that this is an area in which digital
    cameras beat film. After all, the semiconductor fab is pretty good at
    making chips that are really flat and stay that way.

    Stephen H. Westin, Oct 28, 2004
  17. Yes... in astronomy, a major advantage of CCD and CMOS sensors is that they
    don't bend or stretch. Once you know the distortion of your lens, you can
    measure positions of objects in the sky, relative to each other, very
    precisely. Film isn't so easy because there is always a bit of deformation.
    Michael A. Covington, Oct 28, 2004
  18. Stephen H. Westin

    Bob Monaghan Guest

    again, see http://medfmt.8k.com/mf/flat.html for discussion and some
    published tests and reports etc. for both 35mm and 120/220 film stocks
    on film flatness, buckling, and effects on images. Curiously, 35mm (rolled
    up tightly in cartridge) and 120 rollfilm have opposite recommendations
    for timing shots for optimal film flatness after advancing the film, due
    to these differences ;-)

    this is a major reason limiting the utility of fast lenses and high
    resolution lens designs, esp. with 120 film (220 is twice as flat per
    Zeiss tests etc.). Other issues like focusing accuracy (mf/critical.html)
    also limit our ability to accurately focus etc.

    some high end lens/camera makers produce vacuum backs to help flatten the
    film in use for optimal flatness, but the major users of such technology
    remain military recon and similar critical users where $ are not critical

    regards bobm
    Bob Monaghan, Oct 30, 2004
  19. Stephen H. Westin

    Bob Monaghan Guest

    yes, planar sensor devices are potentially superior to film in terms of
    flatness. But the problem is that film remains much higher resolution
    (with its sub-micron grain structure) than sensors (most of the better
    ones of which are tens of microns in area). In general, this is less of an
    issue as depth of focus at f/stops past f/4 or so is sufficient to hide
    minor film buckling. And other errors, like mis-focusing, can be even
    larger and more problematic.

    an interesting chart from Photography for the Serious Amateur, Eugen J.
    Skudrzyk (Physics Ph.D.) at top of http://medfmt.8k.com/mf/critical.html
    shows that very small errors (0.05mm to 0.1mm) in focusing can cause the
    loss of up to 50% or more of the potential lens resolution. There are some
    patented focusing systems which could greatly reduce misfocusing (cf.
    messraster), but the costs of high end cameras using this custom setup
    would more than double, so the industry has avoided this costly solution.
    The switch to slower lenses (zooms) and faster film is another approach
    but means consumers can't do narrow DOF photography with fast lenses ;-(

    there are a number of reports (see mf/rangefinderp.html) of problems with
    some older thread mount lenses (e.g., LTM..), esp. those on modest cost
    Soviet or Russian optics and cameras, being off register slightly (poor
    Q/C at Soviet factories being blamed etc.). Adjusting the lenses to the
    proper lens registration distance (or the russian cameras in the
    alternative) provided major improvements. In other words, this shouldn't
    be a big problem with most Japanese etc. 35mm SLR cameras, even using the
    better third party lenses. Heavily worn lens mounts can be a problem here,
    but again, most of us non-pros are unlikely to wear away the mountings on
    either the camera bodies or lenses ;-)

    it is pretty easy to check for this problem, shooting a fast lens wide
    open etc. Other tests include removing the lens and using "bulb" setting,
    expose the film (you lose a shot or two). Look at reflection of straight
    objects on the film surface. If you see any waavy or non-linear lines
    where they should be straight, you have visual evidence of a film buckling
    problem. This is more common on larger medium format film backs than 35mm.

    regards bobm
    Bob Monaghan, Oct 30, 2004
  20. Stephen H. Westin

    Stephen Westin

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