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Other than flash sync speed compatibilities, is there an impact on the image taken with a leaf shutter as opposed to focal plane shutter?
Since the middle of the image is exposed ever so slightly more than the edges, does that impact luminosity in the image? Would it cause a bloom effect?
Or is it so subtle that it takes a pixel peeper to see it?
Thanks!
My understanding is that depending on the aperture and shutter speed combination, there can be some vignetting. The usual explanation is that for wide open apertures and high shutter speeds (where the shutter is partially open for a greater percentage of the exposure and isn't masked by the aperture blades) the shutter blades act as a second aperture, darkening the edges. Perhaps this is the reason that most leaf shutters top out at about 1/500? I don't recall ever seeing obvious vignetting with the medium format and large format cameras I used back in my film days, but maybe I wasn't looking.
There can be visible differences between a leaf shutter and a focal plane shutter when the slit of the focal plane shutter is small compared to the picture and something in the scene is moving fast.
Basically, motion blur at short shutter speeds will look different. Imagine a car zipping thru the frame horizontally, and a focal plane shutter traveling vertically. The car will look a little skewed, since the top and bottom are imaged at different times. With a leaf shutter, everything is exposed at the same time, so the subject will just be blurred in the direction of motion. Note that this blurring will happen with the focal plane shutter too, since the exposure time is the same. Both will be equally blurred, but the focal plane shutter picture will also show the car skewed.
Flashing, like florescent lights and some LED lights, will look different too. With a focal plane shutter you sometimes get bands of light and dark since different parts of the image were exposed when the lamp was bright and when dark. With a leaf shutter, the entire image will be too light or too dark, assuming you set the exposure for the average illumination.
There is NOT vignetting based on the center having a slightly longer exposure!
Leaf shutters are positioned very near the aperture of the lens, such that inefficiencies created by non-instantaneous opening and closing cause aperture weirdness, not vignetting.
So you get a little bit of f4 mixed in with your f2.8. And half as much f5.6. and so on. May be slightly significant wide open at max shutter speed, but mostly entirely invisible.
One important characteristic of leaf shutters not yet mentioned is that they contribute less shake. The first curtain strike of a focal plane shutter is especially a problem on larger formats. The Pentax 67 is legendary for the hit it delivers.
A lot of leaf shutters are optimistic about their top speeds. Mamiya eventually acknowledged that their Seiko shutters weren't really making the claimed 1/500th and started using an out-of-pattern 1/400th as their top speed. So it's not unusual to find a shutter that's accurate at most speeds but overexposes at its top speed.
