Something Ektra Special

Discussion in 'Classic Manual Cameras' started by hunter_compton, May 8, 2021.

  1. If you know vintage Kodaks, you probably are aware of this camera. It's the Kodak Ektra, Kodak's 1941 attempt to produce the worlds finest 35mm interchangeable lens rangefinder camera, beating out contemporary Leica and Contax cameras.

    Being a Kodak collector, this is one of the cameras I have lusted over for the longest time. It's the one of the finest cameras to ever come out of Rochester and the finest American rangefinder ever made, but with only 2000 made, they command ridiculous money in the market.

    After a few years of watching various action sites, I finally came across one that didn't cost me an arm and leg. It's got some problems, the shutter is jammed (quite typical) but the curtains and their straps appear to be in good shape. I also need to locate the auxiliary 35mm finder window for this lens or a 50mm Ektar lens to go with it.


  2. Wow! I've often looked at Ektras on the auction sites, but as I never seem to win at Lotto my lust has gone unrequited. I'm delighted that you've managed to acquire one, Hunter, and further pics of and from the camera would be nice. That 35mm f/3.3 has a great reputation, and the 50/1.9 would be icing on the cake. Thanks for showing!
  3. I've already got it apart, so more photos will have to wait. Unless you want to see some under the hood, which I'm sure you do. I got the shutter unjammed, and the curtains are in good shape with no broken ribbons or pinholes. I'm guessing it jammed when someone tried to change the shutter speed without the shutter being cocked. The curtains appear to be rubberized nylon, but they may also be silk, I'm not an expert on material science. It's working fine from 1/25 to 1/1000, but the slow speed escapement and self timer are gummed up with old lubricant and will need to be cleaned out.




  4. I was watching a 'live' auction the other day that had an even rarer Ilford Witness on offer.

    The hammer price was a staggering £14000 - plus auctioneers commission and tax adding another 37% to the cost.

    Some people must have pockets a mile deeper than mine... and a lust for old cameras that's a lot more driving.

    I'll settle for the boxed and 'as new' Voigtlander Vitessa left to me by my late uncle. A nice but weird design, and not fetching much money at all for such a well-made oddity. And it has a combined view-rangefinder.

    I'm assuming that the two chromed buttons/thumbwheels at the sides of the Ektra are for releasing the back?
    Fiddlefye and ] like this.
  5. Although I have a great deal of respect for Eastman lenses, as well as a grudging respect for some of their cameras (including the one of this post), I had a scarring experience with the Signet 35* in my youth -- so my feelings here are mixed.

    All the same, good for you.

    * look at the operating controls and remember that this one was from 1953 for a "consumer" product
  6. ]


    The only 35 mm rangefinder I know to exist, which makes Zeiss Contax IIIa look simple. Outdoes the Germans on complexity alone, and that takes derring-do. Beautiful USA mechanical engineering and optical art right here in this thread. Rara Avis!!!
    James Bryant likes this.
  7. A family resemblance...

    Medalist copy.jpg
  8. On looking at the small collection of old Kodaks I have, I think the closest relative is the Kodak 35 Rangefinder, launched in 1938, about 3 years before the Ektra. It's an improved version of the Kodak 35, that lacked the rangefinder. It seems to share a common design concept in respect of body and fittings. Perhaps the Ektra might be considered an evolution...

    I don't mean to hijack your thread, Hunter, but I thought this might be of interest.

    Kodak 35 copy.jpg
  9. So much more complicated than a screw mount Leica. But they had to to work around Leica's patents the elegant shutter and RF coupling, just like Zeiss Ikon did for the Contax.
    The "style" of the engineering reminds me of a Kodak Supermatic shutter. Lots of steel stampings. But the Supermatic is a tank, where the Ektra is known as temperamental.
    By comparison, a Contax has a very refined "machined" look, and there certainly aren't many stampings in a screw mount Leica.
    Fiddlefye and ] like this.
  10. I can honestly say that I am not a fan of (Rochester) Kodak's design language of this period.

    Normally there is something at least admirable in brutish function over form, but I really struggle with these ones.

    Pretty, they are not.

    Look forward to seeing the rebuild and resulting photos though!
  11. I agree with Steve that it's not an attractive-looking camera - except maybe in a steampunk way. But probably hurriedly designed and rushed into production when WWII rudely interrupted Kodak's production in Stuttgart and its supply of Schneider and Rodenstock lenses.
  12. Continuing to post a couple photos of the Ektra's internals, as I don't think there are any elsewhere on the internet and I want to have some archived in the event another brave soul endeavors to take theirs apart.

    The Ektra shutter is normally referenced as being unique, but normally the commentary ends there. Sometimes it is mentioned that it runs left to right and that the gap is preset before the shutter fires. Other notable features I have discovered are that the gap between shutter curtains is not fixed, but actually on a geared reduction that changes the gap between the curtains as they traverse the film gate with the gap growing slightly narrower as the shutter accelerates. This means the exposure is more even as the gap is widest as the shutter is moving slowest and vice versa. There is also a rack and pinion system built into the shutter winding shaft which allows the tension on each strap to be adjusted. The gear train retard systems for the slow speeds and self timer appear to be very similar in design or adaptations of those same systems on a Supermatic shutter.

    Overall, very unique and mechanically intricate design. I can see why it has a reputation for being difficult to service, but in reality it's different not difficult.

    IMG_0221.jpg IMG_0222.jpg
  13. What?!
    That would surely result in a more uneven exposure, not less?
    E = I*t

    Consider the extreme case of the trailing blind catching up with, and capping, the leading blind.
  14. No, you are correct. That's a mistype on my part. I should have said that the gap is at its most narrow when it starts and widens as the curtains accelerate, as this is a more accurate description of the mechanism.
    rodeo_joe|1 likes this.
  15. Interesting concept.
    I can see how the gap can be accurately controlled and adjusted 'on the fly', but not how the blind acceration can be predicted.

    There are multiple forces at work - spring tension, which will decrease slightly with travel; inertia and stiction of the blinds initially; and drag/friction applying a braking effect to the travelling blinds.

    I certainly wouldn't want to predict all that without the aid of a computer.

    Seems far easier to assume a constant velocity and divide the slit-width into that to get an effective exposure time.
    E.g. blind velocity = 500 mm/s; slit width = 5mm; effective exposure = 5mm/500mm/s = 1/100th sec.
  16. The Leica focal plane shutter is also constant acceleration, and the gap widens as the curtains speed up. But the two curtains move independently, all the shutter speed setting does is set how far the opening curtain moves before the closing curtain starts. The spring tensions are independently set on the two curtains. All very well covered by patents, which is why the Contax and Extra shutters are much more complicated.

    The method Leica used to calibrate the shutters was ingenious, a rotating backlit drum with a slit in it.
  17. Yes it was ingenious. I have wondered how you would make an electronic version, Maybe using several row of leds. Anybody have any ideas?
  18. I've been working more on the Ektra when time permits. I already have it together and have shot a couple of test rolls through it (soon to come) but this is a recap of the repair and refurbishment. Fortunately, the 1943 Ektra repair manual is available though Pacific Rim: (warning - 500MB dowload)

    Cleaning the optics and aligning the rangefinder were fairly uneventful other then being tedious. I disassembled the lens to clean the old grease off the helical and re-lubricate. It's much smoother now and collimating the focus with the body was quite easy.

    The optics in the top cover were also cleaned, this was somewhat tiring as the Ektra has five glass optical lenses which make up the variofocal viewfinder and the rangefinder has five prisms and six lenses and my ADHD won't let me leave a single speck of dust visible in any of them. adjusting the rangefinder is easy with one screw doing halving and another doing the horizontal alignment.

    The tricky part has been the Ektra's shutter, mainly understanding the mechanism, since it is similar in some ways to other shutters but it has key differences. I am not aware of any other resource for understanding the shutter either, so other than the above repair manual (which is largely text based and has few diagrams) I am flying into uncharted territory.

    What we know is that the Ektra uses a three drum shutter, much like a Leica, but differs mainly from a Leica shutter in setting the gap between the curtains. On the Leica, the gap is made by delaying the release of the trailing curtain. On the Ektra, the gap is made on the curtain drum before any curtains release.


    So on the Leica, the chain of events is that the shutter is wound with the curtains overlapping, then they stop. The leading curtain is released, then there is a delay and the second curtain is released creating the gap where they both run to the resting position. In this design each curtain is tensioned separately and the tension on each curtain determines the curtain velocity.

    On the Ektra, there is a gap between the curtains as they rest. When winding begins, the leading curtain needs to pick up immediately and close the gap with the trailing curtain so that the film in the film plane is not exposed as the shutter is wound. Once the leading curtain clears the film aperture the leading curtain stops moving. The trailing curtain continues to move and wind around the center of the curtain drum setting the gap. The gap is 0.030" at 1/1000 and about 1.375" at 1/25. The shutter is thus wound and the sear catch releases both curtains simultaneously, running back onto their rollers. In this design, each curtain roller can be tensioned, but the roller drum rigidly couples the two curtains and the differing inner and outer diameters of the drum regulate the curtains so that the gap starts out narrow and widens as the curtains accelerate to give an even exposure.

    The Extra's operation necessitates a complex shutter drum, and this is evident in the following diagram. The center portion which holds the narrow trailing curtain is rigidly coupled to the winding mechanism and speed throw-out. The upper roller for the wide leading curtain is coupled to the center portion of the drum and thus the winding mechanism by two different mechanisms simultaneously, there's a backlash spring on the center spindle which allows the wide curtain to stop and the narrow curtain to continue to wind, but not change the spacing when released. There is also a toothed gear and pawl which limits rotation in one direction only until the drum rotates and centrifugal force pushes the pawl outwards which allows the gap to change once the leading curtain is fully on it's roller, closing the gap and allowing the shutter to blackout when rewound. The lower roller for the wide leading curtain is coupled to the center drum by means of a spring which allows the roller to rotate independently but under spring tension.


    The manual indicates the Ektra shutter went though at least one revision, as it lists a "early" and "late" version when it was published in 1943 with the changes being how the lower roller is coupled to the drum and the late version having an additional ribbon roller. FWIW, my camera is SN 3724 and has an early style shutter. Serial numbers are reported to have started at 1000 and production was estimated at 2000 to 2400 examples. Make of that what you will.

    Understanding the operation of the shutter I still had to take it apart to clean the bearings and thus remove the curtains to do so. Lots more intricate work. Cleaning the bearings necessitated removing tension of the rollers, so I notated the number of turns on each roller for later, but preliminary settings are also listed in the repair manual.


    With the shutter cleaned and reassembled the next question was, as Greg suggested, calibration. The repair manual lists tolerances for each shutter speed, but with both roller tensions, the curtain slit width and the speed control throw-out all having control over the shutter speed and being interactive controls, the need to measure the effective shutter speed and its evenness is imperative.

    Kodak referenced the "Ektra shutter speed tester" in the repair manual. I have little other details on it, but the tolerance list would suggest that it output a singular or average shutter speed in milliseconds, and I believe it to be the apparatus shown below:


    I don't have such an apparatus at my disposal, and likely none exist at this point in time. In the past, I have used a photo-diode and bright light to output a signal to a program like Audacity to measure shutter speed. This is fine for a leaf shutter, but a focal plane shutter requires at least two measurements to ensure that the shutter is traveling evenly over the film plane. Some modern focal plane shutter testers use 3 to 5 sensors, but professional models like those made by Kyoritsu can cost hundreds to thousands of dollars.

    With that in mind, I built my own shutter tester to test the Ektra's shutter speeds. It uses lasers and two photo-transistors biased as photo-diodes. The sensors are mounted about 30MM apart giving an effective speed based on gap width and velocity at the start and end of the shutter's travel. The key attribute is that each sensor is under an aperture of only 0.030" which is the narrowest gap of the shutter, which gives a point estimation of shutter speed. The signals are output though a stereo connector to my computer running Audacity which allows me to compare the signals and given the specs of my sound card, This allows me to resolve the shutter speed down to 0.1 ms with an accuracy of +/- 0.02 ms (1/1000 is 1 ms).


    With this in hand, I've been able to calibrate the Ektra's shutter to its original tolerances and reassemble the camera. I've already shot some test rolls, including a roll of Provia 100F to confirm even shutter travel and will develop and scan tomorrow.

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