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

[RalphLambrecht]

Doremus

I think your calculations are realistic. I think to remember that the shutter error can be as much as 2/3 stop at fast speeds and small apertures, but as Ian said above, that combination is unlikely due to film speeds and normal lighting situations. Your numbers are more 'real' world, and as you say, normal shutter speed variations are also within 1/3 stop. Sometimes they compensate, but unfortunately, in some cases (such as in cold weather conditions), they can also add to the problem.

By the way, these shutter issues are the reason that I advise against in-camera exposure series for film testing. Using a transmission step tablet is the best way to get an accurate exposure series.

 

[holmburgers]

Thanks everyone, some great links and good insights to boot.

 

[lxdude]

Oh, and by the way, why don't we keep personal tiffs between members hidden away in private messages.

And jpegs, too.

 

[jackd]

Why not test it?

It is pretty simple to put your lf lens on the front of a digital camera with cardboard and tape to test the amount of transmitted light directly. Digital cameras have very low reciprocity so you can just open the digital shutter, trip the leaf shutter, close the digital shutter and then change the fstop/shutter and try again. Just make sure to use a constant light source - in other words, don't do it on a day with many blowing clouds.

In my experience, shutter efficiency is completely masked by other factors such as shutter speed accuracy, metering accuracy, bellows extension, development accuracy etc.

It is not something I worry about.

 

[Pupfish]

FWIW, you can see and compare the shutter propagation time graphically, when a photocell tester running through your sound card port using a sound editor like Audacity.

After testing my Copal O's and 1's and Rapaxes shutter propagation time is not anything I'm overly concerned about-- even shooting a lot of transparency film.

Bigger deal is that all of my shutters run about 1/2 stop slow on 1/500 or 1/400.

 

[RalphLambrecht]

FWIW, you can see and compare the shutter propagation time graphically, when a photocell tester running through your sound card port using a sound editor like Audacity.

After testing my Copal O's and 1's and Rapaxes shutter propagation time is not anything I'm overly concerned about-- even shooting a lot of transparency film.

Bigger deal is that all of my shutters run about 1/2 stop slow on 1/500 or 1/400.

Could you post a sample graph? Sounds interesting.

 

[Pupfish]

No, sorry. I don't have time to set this up right now to write a tutorial, when so many on this topic already exist. (There are literally dozens of threads here and elsewhere in the archives).

 

[Bill Burk]

I like jackd's idea of using a digital camera to measure the shutter.

Now I have a use for that thing.

Yesterday I got busted in the mountains with it around my neck. "I thought you stood for something" Reed said as he stared perplexedly at me.

 

[RalphLambrecht]

No, sorry. I don't have time to set this up right now to write a tutorial, when so many on this topic already exist. (There are literally dozens of threads here and elsewhere in the archives).

I asked for a sample graph not a tutorial. Never mind, can you post a link to any of these threads? I couldn't find it.