"Real" max/min aperture on Elmar 5cm/3.5 ?

Discussion in 'Leica and Rangefinders' started by markwilk, Jun 28, 2019.

  1. I'm just about to finish the first roll through my first Leica (IIIc), Leitz Elmar 5cm/3.5 collapsible. I noticed something about the lens last night, and thought I'd ask the question.

    This lens advertises a max/min aperture of 3.5/16. However, the marker on the the aperture ring on the front of the lens will rotate slightly beyond the 3.5 and 16 indicators on the scale. (see attached images) It's not much, but it definitely does open/close the aperture more as I move beyond those indicators. I really notice the difference when I move beyond f/16.

    I'm sure others have noticed this. Does anyone have a sens of the "real" max/min aperture of this lens?



    beyond_3_5.jpg at_16.jpg beyond_16.jpg
  2. Not enough to make a difference. The marked f/stops are only approximately correct, and do not include loss in transmission. Without coating, each glass-air surface reflects about 10% of the light, and there are 6 surfaces in an Elmar lens.
  3. You'd need to shoot some narrow latitude slide film and do some testing, taking good notes to probably in the end not see that much to it.

    With color negative or black & white print film, you'll most likely never know with all the latitude those films provide.
  4. SCL


    Basically it's irrelevant. Lens mfrs typically choose to print or indent commonly used aperture markings because that is what people are used to and meters indicate, even though the diaphragm may be able to move slightly beyond the min & max...there just isn't enough room to include oddball markings.
  5. Dustin McAmera

    Dustin McAmera Yorkshire, mostly on film.

    It wouldn't surprise me if you have something like f/22 at the small end. It certainly looks like a whole stop on your picture of the scale. But if you could get any more than f/3.5 at the other end, Leitz would know about it and wouldn't have sold the lens as f/3.5. Even if the iris moves any more, I'm sure it's beyond the edge of the useful glass at that point.
  6. Its insignificant and I wouldn't spend much energy thinking about it.
  7. Thanks for the replies, all!

    Dustin: with my untrained eye, I'm inclined to agree with you. That's the reason I included the picture with the marker at 16 and the picture with the marker beyond 16: the distance the marker moves beyond 16 is about the same as the distance between 11 and 16. In other words, maybe a full stop.

    Now, is 16 really 16? And is the edge of the range 22? I have no idea...and for what I'm doing with the camera (and the latitude with the negative film I'm using, Greg M), it's not that big a deal.

    And although I didn't include comparisons of 3.5/beyond 3.5, the iris was at the edge of the glass at that point, so it would make no difference.

  8. I doubt its f22 or less then 3.5
  9. SCL


    If it is f/3.35 or f/16.28 does it matter? NO!
  10. Dustin McAmera

    Dustin McAmera Yorkshire, mostly on film.

    Of course this matters; of course you care whether your camera has f/22 or not! And if I'd paid for a *Leica* I'd certainly expect the engravings to be accurate. But anyway, you can see clearly in the OP's pictures that the distance the index goes beyond the f/16 mark is quite comparable to the distance between f/11 and f/16; and that on a scale where the marks get progressively closer together; so I think I was right to say perhaps it's f/22.
    I don't have a Leica; the Industar-50 on my Zenit 3 has a hard end-stop right at f/16. I think (it's not here to check) the I-22 on my Zenit 1 is the same; but these are rigid lenses, not collapsible like the OP's Elmar.

    I have some old scale-focus cameras (front-element focusing lenses on folding cameras) where the lens will turn some way beyond the last scale engraving. There's no way to use that last bit of adjustment, and and I wonder why a maker would leave it like that. Finally I bought a camera where a previous owner had made his own extra engravings to use the closest focus he could. I've used them myself; he got them about right.
  11. Reflection for a n=1.5 surface is 4%. You would need close to n=2 to get 10%.

    But yes, you still lose a lot of light with six surfaces at 4%.
  12. Or, you could just fit the lens to a digital camera and immediately see the result on a histogram.

    I suspect that setting the aperture ring beyond the maximum aperture marking does not actually let in any more light. It's quite common to see iris blades that open beyond the physical diameter of the glass elements. Then the edges of the glass limit the aperture, which isn't a good idea since the iris blades also act as anti-reflection baffles.

    At the other extreme, it's also common to have iris blades that close beyond the 'minimum' aperture. However, closing an iris beyond its design limit isn't a sensible thing to do regularly. It can cause the iris blades to 'bite' into each other, and distort the iris assembly into a bulge, rather than staying flat. Plus, as others have said, the aperture markings are more of a guide than a laboratory-accurate calibration.
    Last edited: Jul 14, 2019
  13. I stumbled across this thread because I noticed something similar on an Elmar 50mm 2.8. I can turn beyond f16 changing the aperture.
    I was worried that this was a problem but it seems it's a feature of Leica lenses ?
  14. It is not unique for Leica lenses. Several of my manual focus Nikkors can move a little bit beyond their outer click stops as well. I think you notice it less because they kind of slide back into the click position, but the aperture does open/close more/less beyond the click.
    jimnorwood likes this.
  15. I'm pretty sure that this is just "slack" on the old lenses,
    But many modern long /zoom lenses have focus variation/extension built in to accommodate expansion and contraction in different temperatures.
  16. A common design feature of older lenses, and meaningless.
  17. Usually 4% for each interface air-glass interface. 8% for air-glass-air.

    Fresnel equations - Wikipedia

    OK, 8% for n=1.8, which might be true for some elements of modern lenses.
  18. Hmmm sounds suspicious. Has Leica been hiding something from us all these years? That's a nice lens if in good shape. Love to see some pics taken with it.
  19. Barry, your wishes are orders to me :)
    (the three year 2005)
    003a Ultramarinos Elmar5 f8 1-60.jpg Leica IIIc. Elmar 5. 1/60 at f8. Tri-X 400. D-76 (1:1) 9' at 21ºC

    006L&R Mujer y Taxi Elmar5.jpg
    Leica IIIc. Elmar 5. 100TMAX. TMAX dev. (1:4) 8' at 20ºC

    018a Nikons Elmar5-NOKKY f16 1 segundo.jpg
    Leica IId. Elmar 5 + NOOKY. TMAX 400. TMax dev. 7' at 20ºC (1 inversion per minute)​
  20. Great images Louis. Love those F and F2's.
    luis triguez likes this.

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