The effect is indeed rather the opposite as what has been said before. Shutter efficiency issues at small apertures lead to too long speeds and overexposure. Not to too short speeds and underexposure.
The effect is real, and you should allow for it at (usually) the top speed of the shutter, 1/500.
It is, by the way, why the big Mamiyas have a 1/400 top speed marking instead of 1/500.
And that is about the size of the effect too. A bit more perhaps: upto just under 1/2 stop overexposure at 1/500, depending on the aperture used, of course.
A focal plane shutter, by the way, also suffers shutter efficiency problems, though not aperture dependent, but depending on speed and distance to film.
I remember the subject being discussed in magazines and books back in the 70's, when there were quite a few leaf shutter lenses in use as a percentage of the market. It wasn't an issue with strobe light, for obvious reasons, but with ambient light, high shutter speeds caused an uneven exposure at the edges of the frame compared to the center. There was only so much tweaking that could be done to compensate, as pushing the exposure at the periphery of the frame tended to overexpose the center. The effect also caused some unique funky looks to stop motion shots that had no parallel in the focal plane shutter world.
I think this is the reason some companies limited top speed to 1/400 sec, as even with modern shutters having fast opening and closing times, the problem would begin to appear at 1/500 sec unless the lens was stopped down pretty far. It's been a long time since then, but I could swear that there were some charts from Hasselblad Paillard back in the 70's that mapped out problem shutter/aperture combinations. Then again, there was a soft-cover magazine sized book about a half inch thick titled "Medium Format Cameras" or something close that I recall tackled the subject. Maybe someone here still has that book, and can let us know if I'm thinking about the right book....
The effect is indeed rather the opposite as what has been said before. Shutter efficiency issues at small apertures lead to too long speeds and overexposure. Not to too short speeds and underexposure...
isnt the optical aberrations going to be a greater issue than shutter efficiency at wide open apertures given that lens correction is optimised for f16/f22?
Which makes me think of the mounting of packard shutters in camera.
If a 5 inch packard was mounted in camera and fired at 1/15 sec., would there be a difference in exposure if you used a lens with a 5 inch diameter glass or a lens with a 2 inch diameter glass at the same f stop? I suppose there has to be.
"There are a great many things I am in doubt about at the moment, and I should consider myself favoured if you would kindly enlighten me. Signed, Doubtful, off to Canada." (BJP 1914).
Ok, I found an eBook that talks about it. Page 8 & 9, and it actually gives a table. Though I'm not sure what the left-most column means. It says "When the lens is closed down by (stops):......" Does that mean closed down from maximum aperture? Kind of a weird way to word it, eh?
Thanks to those who attempted to answer my question instead of just dismissing it as fretting over particulars.
#4 in this thread, "And by shutter efficiency I'm talking about the phenomenon that a small aperture get's a more "perfect" shutter cycle than a large aperture, which is particularly a problem at high speeds where the time it takes to open & close is a higher % of the total shutter time."
I think the convention is : a large stop is a lower number, not higher IE:2.8= a large stop & 16= a small stop. that's why it called "stopping down"
This depends on whether you're looking at the f number or into the lens
A motorcyclist is the only one who understands why a dog rides with it's head out the window.
"I had an idea once, it died of loneliness"--George
I'm not trying to be pedantic, I just want to know.
Seriously, I was just answering your question when I said 'ignore it' as that is the guideline many follow with negative film where a slight overexposure is inconsequential
are there any steadfast guidelines that one can go by?
I, like you, am also curious, and if I wanted to quantify the effects I'd break it down into two possible paths of discovery.
One path would be an emperic method. For example, you could plot exposure at the film plane vs aperture for a number of apertures and quantify the deviation from a straight line by using a curve fit and then making an equation that would solve your variable based on the curve.
The other way would be to do an a priori calculation. In which case you would need to know the size and shape and velocity of the shutter blades, and some complex math to associate bizzare aperture shapes with their light passing capacity etc.
Realize that in both cases results would apply only to the system tested or mathematically evaluated because shutter shape and velocity is not standardized.
Originally Posted by ic-racer
I'd just ignore it and worry about something else
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