continuous speeds on M6: true or false?

Discussion in 'Leica and Rangefinders' started by fran_ois_courtois, Feb 27, 2005.

  1. Hello,
    I've been told by a quite knowledgeable person that:
    "contrarily to a common thought, the M6 allows for continuous speeds if you set the ring in between 2 steps"
    Of course there is a obvious lack of precision in doing this, moreover because the metering diodes do not react in between (while they do for intermediate steps on the aperture ring), but still this is for me a surprise and could be useful sometimes as I always work in "aperture priority mode" and hate going back to the aperture setting for a half stop adjustement
    Ok, but the question is, IS THIS TRUE, have you guys already heard of this undocumented feature, and is it also the case for the other bodies: M6TTL, M2, M4, ... ???
     
  2. It seems to be true for my M4 as well, but it doesn't really matter, since there's no way to be accurate. That is, if you set it in between 1/60 and 1/125, will you get exactly 1/90? How can you tell what you'll get anyway?

    M7 has got stepless speeds, so if you do AE, I think you can get very weird speeds which are what the meter recommends. But if you're shooting negative film, I don't think it really matters anyway-- too many variables from temperature to development time to agitation, etc. that will introduce many unknowns. And with the wide latitude of negative film, does it matter if you're 0.25 stop off?

    If you're using slide film, I would argue it doesn't matter anyway, unless you can be sure you're metering a completely gray subject. Even then, 0.25/0.5 stops is still within lattitude of slide film.
     
  3. I think all mechanically timed focal plane shutters work this way, there are just click stops for convenience.
     
  4. Just look at the blades when you jiggle the aperture ring between stops, if
    they move, then there's your physical evidence. Even if the diodes aren't
    registering it the film surely is.
     
  5. AFAIKR (as far as I can remember) the cam on the Ms is nearly smooth but has positions with a slot to allow bending of the cam, yes bending. Therefore the 'intermediate' speeds will be there just not calibrated and could even be the wrong way. The 1/1000th position is an extension of this cam that can also be bent to adjust the 1/1000th time, that is what the little black plug near the speed dial on a M6 is for.
     
  6. There are cameras where in-between speeds are definitely unpredictable. The Topcon Super-D, the fine tuning of the cam is done by hammering it thinner if you need it to stick out more at that speed. These bumps are not kept smooth between the speeds.
     
  7. do you think it is harmful for the camera to use it at intermediate speeds?
     
  8. Francois, as has been said you will get intermediate speeds but there is no way to get an exact speed. You can get one or the other of the marked speeds as much as 3/4 the way between the clicks, then suddenly get an intermediate speed just before the next click. The exception is the M5, whose shutter cam is designed for a smooth progression between speeds in the slow and fast groups, to go along with the meter movement. This is also the case with Leicaflexes.

    Huw, the little black plug behind the speed dial is for the slit-width eccentric adjustment, which affects all speeds but 1/500 and 1/1000 the most. The 1/1000 cam adjustment is made from the front of the camera with the top plate and the mylar rangefinder baffle removed, by slightly tweaking the cam extension.
     
  9. Ben,

    I always assumed the hole was to get at the 1/1000th bendy bit, yes the 1/250, 1/500, 1/1000ths are adjusted as you say. I have never looked down the hole, just assumed as it is in approximatly the right place. (well until 20 seconds ago) Thank you for clearing this up for me, I now see what it does. Funny the M6 adds this 'no need to pop the top' feature and messes up the vertical RF adjustment!
     
  10. i have 3 M-3 `s with their respective original manuals. in one of those
    manuals, ( only one), it says that you can set middle speeds in the range from
    1/50 to 1/1000. my M-6 manual does not says anything like that.
     
  11. Don't forget that outside the M7, the higher shutter speeds on any M may be off by a 1/3
    of a stop anyway. Can't be helped.

    So as others have noted, intermediate speeds above X sync are anyone's guess. Above 1/
    250th and this includes the set speeds as well :?)
     
  12. From the M4 Manual, p.14: "Intermediate shutter speeds may be set between the click-stop settings, except between 1/8 and 1/15 sec." Those demarcate the slow- and high-speed escapements. Intermediate settings on the slow escapement are audibly discernible. With its mechanical shutter, the M6 should operate identically.
     
  13. Yes, the M6 shutter speed timer is essentially the same as the M4 and all M bodies other than the M5 and M7. The reason the owners manual in the M6, M6TTL and MP omits the reference to intermediate speeds probably has to do with the fact that the meter doesn't recognize intermediate speeds. However if you have a chance ever to put your M bodies up on a shutter tester, you can prove to yourself that setting the dial midway between markings rarely results in a half-stop speed, the sole exception being the M5, which has a different, stepless shutter control mechanism designed to interface with the stepless meter.
     
  14. Just ran my M6 on the shutter tester. Yes all speed settings will give intermediate speeds between the click stops, except between 1/8 and 1/16. But why "split hairs?" There are other variables in the process. And setting intermediate speeds is unpredictable. The accepted tolerances on most shutters is such that I would rather set the M6 speeds on the mark, and select intermediate lens apertures. For example accepted tolerances for 1/125 sec is between 6.64 and 10.16 milliseconds with optimum at 7.812. Why not have your m6 tested for calibration and use speeds you can depend on. Then work on the other variables.

    J
     

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