Shutter Efficiency w/ Leaf Shutters & Higher Speeds...

[holmburgers]

Hi everyone,

So I'm looking for a practical way to determine the effect & degree of shutter efficiency at high speeds and small apertures.

Or, rather than determine it myself, are there any steadfast guidelines that one can go by?

I read the Leslie Stroebel book and she (he?) has an elaborate method to test this using neutral density filters. I don't have any and I'm not gonna go buy any just to test this, nor do I wanna go thru a lot of film to figure it out (I know, I'm lazy and cheap! )

I have electronic readouts of my shutter speeds, so that variable can be eliminated, but if anyone has done some tests themselves & would like to share, I'd love to know.

For what it's worth I have a Synchro-Compur in a Schenider 180mm/315 Symmar (convertible type, the golden oldy)

[RalphLambrecht]

How do you have electronic readouts for large-format shutter speeds, and what else do you need to determine shutter efficiency? I'm failing to understand the problem.

[Ian Grant]

High shutter speeds and small apertures don't really go together in practice.

I live in a region where once the sun comes up it's almost maximum readings in my light meters all day, and even a 400 ISO film at 400 EI doesn't allow maximum speed and smallest aperture, and that's why Strebel has to use ND filters.

It might surprise you that I do use 400 ISO films , actually HP5 @ 200 EI because I need to work hand held and stop down well, but the fast shutter speed/small apereture is never an issue.

Ian

[holmburgers]

Well, I sent it to Paul Ebel and he told me the actual shutter speeds (from an electronic tester). I don't own one.

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.

[holmburgers]

Ian,

Stroebel doesn't use ND filters for the purpose of exposure, but for the purpose of testing this phenomenon.

And regardless of the fact that yes, I'll probably never need to use f/22 and 1/200th, I'd like to know at what point this becomes an issue.

But you're probably right that I won't run into any problems.

However, at what shutter speed would one theoretically need to start thinking about shutter efficiency?

[Ian Grant]

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.

It's theory rather than reality, when you've been using a wide variety of camera's and lenses for years you'll realise eventually

Ian

[holmburgers]

Alright, I'll take your word for it.

But when my million dollar picture is ruined because of shutter efficiency, I'M COMING AFTER YOU! just kiddin'

[RalphLambrecht]

Well, I sent it to Paul Ebel and he told me the actual shutter speeds (from an electronic tester). I don't own one.

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.

The issue is simply due to geometry. As the shutter opens, a small aperture is quickly revealed, while a larger aperture needs to wait until the shutter has fully opened. This can lead to underexposure with large apertures and fast shutter speeds, because the shutter delay becomes a significant portion of the the entire exposure time. Opening and closing the shutter usually takes 2-3 ms each. However, in practise it is rarely a problem, because large apertures and fast shutter speeds are not the norm with large-format photography, and some of the delay is taking into account by the maker of the shutter by adjusting the timing and assuming medium apertures.

If you still want to test, use your friend's shutter tester at max shutter speed and different aperture settings.

[ic-racer]

However, at what shutter speed would one theoretically need to start thinking about shutter efficiency?

I'd just ignore it and worry about something else

[holmburgers]

Thanks for the reply.

I'm familiar with the mechanics of it, but I've heard that manufacturers calibrate for large apertures, so that at small apertures and high speeds you actually overexpose.

Either way, Paul Ebel is a repair guy & I don't think that a shutter tester would tell me what I need to know (but it seems like I don't actually need to know this)

Though!.... I'd still like to.

Knowing that it takes 2-3 milliseconds might help me in calculating the degree to which it might be a problem.