Lens register chart

Some time ago I took the trouble to take Willem-Jan Markerink's
excellent table of lens registers (flange distances), tidy it up, and
sort it by flange distance. I also added the Sigma SA mount and
corrected the Miranda entries (since there was really only one Miranda
dual thread/bayonet mount). See the result at

http://www.graphics.cornell.edu/~westin/misc/mounts-alphabetical.html

and

http://www.graphics.cornell.edu/~westin/misc/mounts-by-register.html

 

westin* (Stephen H. Westin) wrote in

Nice!

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


/Roland

 

No. Do you? If so, I'll add it.

 

While you are doing that, add the Nikon Rangefinder mount.
Jim

 

Which I don't know. As I recall, it was based on the Contax mount, but
used a different ratio on the rangefinder cam.

 

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?

 

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.

 

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:
http://www.9000.org/index.php?page=technical_details

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 ;-)

 

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.

 

--
***********************************************************************
* Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
********************Standard Disclaimers Apply*************************

 

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
Tom
endquote

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.
end-quote:

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

 

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.

 

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

 

And Kodak Technical Pan was roughly 2/3 the thickness of Tri-X Pan.

 

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
www.covingtoninnovations.com/astromenu.html

 

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.

<snip>

 

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.

 

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

 

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

 

Well, after more than a decade at the same address, my list has moved to

http://stephen-westin.com/misc/mounts-alphabetical.html

and

http://stephen-westin.com/misc/mounts-by-register.html