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  1. #1

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    Sep 2002
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    I have a Nikkor 90mm f/8 lens. The shutter (Copal #0) goes up to 1/500. If I use it with flash or strobe will it sync at 1/500, or is there another widely-used shutter speed? Thanks!

  2. #2

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    It will sync up to 1/500. Flash is much faster than shutter speed and since you are opening the shutter completely when you actuate it, the film will get fully exposed. Sync speed with LF is usually better to control the amount of ambient light you want in your shot.

  3. #3

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    Sep 2002
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    Flash isn't always that fast - only at low or mid-range power. At or near full power some units have quite long discharge times - longer than 1/500th at any rate. At full power my Metz 45CT3 has a discharge time of 1/300th, and I think (although I've never measured them) that my studio monolights are even longer than that.

    OTOH, although the Copal 0 shutter speeds go up to 1/500th, there is a fair chance that they will be rather slower than that, so it may not matter in practice.

  4. #4

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    A leaf shutter has sync on all speeds. A focal plane shutter on the other hand, usually has a max. sync speed that is much slower than its fastest speed. Both, your leaf shutter and your flash are not “digital” in their operation. Light intensity increases as the leaf shutter opens and decreases as it closes. When the flash is triggered, it rapidly reaches its peak light volume and then “burns out”. Both processes take place within fractions of a second and usually cannot be observed with the naked eyes. While the focal plane shutter has a very small time-window when both curtains are open, the flash light might not have finished when the second curtain start to close. This is not the case with a leaf shutter. Although a leaf shutter may cut the flash, too, the effect will be an underexposure but not a partial exposure as it would happen in case of the focal plane shutter.

    The specs of a studio flash usually contain one or two of the figures “t 0.1” and “t 0.5” (usually for max. load). These figures specify the amount of time the flash needs to reach 1/10th (or 1/2 respectively) of its maximum intensity after being fired. The values for t0.1 can be as long as 1/60s for very powerful flashes and is usually shorter than 1/500s for lower energy or compact (battery) flash lights.

    The shutter speed is usually determined by the desired amount of ambient light in the scene. The longer the shutter speed the more weight is on ambient light, as long as the flash energy stays the same.

  5. #5

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    Sep 2002
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    Thanks, all.

  6. #6

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    Sep 2002
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    One of the problems with a leaf shutter is acceleration and deacceleration of the shutter blades. Obviously, the shutter cannot open or close instantaneously because it has mass. If you look at a graph of a leaf shutter opening and closing, it ramps open (slopes up) had a flat open period, and then ramps down to close.

    The exposure period is the total time from the beginning of the edge of the ramp until the trailing edge of the closing ramp. Lenses with leaf shutters have a built in delay (for electronic flash - X-sync) to time the flash to compensate somewhat for the shutter not being completely open when the flash is triggered.

    Here's the problem. The faster the shutter speed you are using with a flash, the greater the exposure problem as leaf shutters are notorious for being inaccurate as they near the peak shutter speeds. Also, the larger the shutter, the greater the problem because of greater mass, etc.

    My advice is to expose at 1/60th second or less using an electronic flash with a leaf shutter because you actually control the light reaching the film with the aperature setting (in most cases) - and the shutters are far more accurate in speed at lower shutter speed settings.

    If you use fast shutter speeds 1/125, 1/250, 1/500, you may find yourself using a larger f/stop or higher flash power setting to compensate for under exposure caused by the shutter open/close cycle.

  7. #7

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    Sep 2002
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    Steve, I think you're confused about the way that leaf shutters sync. The sync is achieved by a switch that closes the circuit across the PC connection, and is physically tripped by the blade mechanism as the shutter reaches the fully open position. Thus the time required for the shutter to open has no relevance - only the time it stays fully open matters. There is certainly no need to restrict yourself to 1/60th or slower.

  8. #8

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    Sep 2002
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    The truth is that most shutters are not able to have the optimum synchronization on the whole scale of their shutter speeds. At both ends of the scale they are deficient, more or less. If well synchronized at the slow end they will lack light at the highest speeds and vice versa. Only special shutters with a fully adjustable delay are synchronized at all shutter speeds (that is the original meaning of the expression "a fully synchronized" shutter).

  9. #9

    Join Date
    Sep 2002
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    With all deference to your Huw-ness, I will render the following on leaf shutter synchronization.

    First, I don't take camera equipment or watches apart as I seem to have a better talent for losing small parts than reassembling the item. So, I have not personally ever taken a large format shutter apart to see or test how it synchronizes - nor do I intend to for the above stated reason.

    Secondly, I can only go on what I was taught in photo school, the information in my photo books, and 35 years of experience.

    What Stroebel says about synchronization is as follows:

    "It is sometimes assumed that because of the short duration of the light from electronic flash tubes, none of the light can be cut off by the shutter and the guide number will remain constant at all exposures."

    "...makes it possible for the shutter blades to close soon enough to prevent some of the light from reaching the film. A test made with one type of electronic flash unit revealed that only 59% of the light was transmitted at 1/500 of a second compared to 1/100 of a second and slower speeds..."

    "Changing the exposure time setting from 1/30 second to 1/500 second reduces the light from a continuous source to approximately 1/17, but reduces the light from flash lamps to approximately 1/4."

    Lastly, all shutters (focal plane or leaf shutters) have a built-in synchronization delay. With a leaf shutter, it can be as long as 30 milliseconds. What the designers are trying to do is get the shutter to the fully open portion of the total shutter open/close cycle before the flash is triggered as you stated. This requires a delay.

    My point being that unless the shutter has a continuously variable delay (most that I know of don't do that), you are better off to use slower shutter speeds with an electronic flash. Or, you will need to do testing to see the change in exposure caused by the faster shutter speed.

    Heck, I could be wrong, Leslie Stroebel could be wrong, the Langford Manual of Photography could be wrong - but...

    This has been borne out in my own inadvertant (OK- mistake) electronic flash exposures. When the shutter was set at 1/250 with the correct f/stop, the transparency appeared about 1/4 stop under exposed. When I changed the shutter speed to 1/15 second with the same f/stop of the same subject it was correctly exposed.

    However, as someone once said, "your mileage may vary with usage..."


  10. #10

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    Sep 2002
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    As I said earlier when a flash is working at high power output its discharge time can be longer than the faster speeds on a leaf shutter. Thus the shutter begins to close before the end of the flash. This appears to be what Stroebel is talking about, and is probably what you have experienced. However, for virtually anything other than full power output most flashes have much shorter durations that the fastest speed of typical leaf shutters, and will be unaffected.

    I reiterate, for electronic flash the sync is triggered by the shutter blade mechanism reaching the fully open position. In other words, the delay you refer to is not something independent of the shutter blades, but is actually part of the same system. This is a direct mechanical linkage and provided the shutter is not faulty there is no way that it can fire the flash before this point. For M-sync it is a different matter. Here the flash is triggered at the beginning of the opening phase and the time to open may indeed have a bearing.

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