Testing lens shutter speeds

[Ian Grant]

Today I sat and recorded the shutter speeds of 3 lenses with quite different shutters.

I was surprised how accurate a program like Audacity is for these these test. (I also have Sound Forge which is better but not Free).

Mainly I've always used LF lenses at speeds of a 1/30th and lower, and my audio tests are remarkably accurate. I was quite surprised.

I've always thought Copal's are lazy shutters and the first to need attention, and have found all my Compurs are far more reliable even the 90 yera old on a 165mm Tessar

Here's a Copal starting at a second

A 1932 surprisingly accurate Compur

and a beast of an Acme 3

All shutters except the Copal run through all speed up to a 1/200th

The point is use Audacity or similar & read the speed off the timeline, it's free you have a PC or you wouldn't be reading this

All the LF lenses I have with me in Turkey (9) fall well between the examples and the shutters are accurate

Ian

 

[Fotoguy20d]

Thanks for sharing this method. I'd heard of using the microphone input and a simple optical circuit but this is much easier. I've had the thought that with a 30fps video camera and simple video editing software you could at least measure the slow speeds fairly accurately but again, your method is much simpler.

Dan

 

[Ian Grant]

I doubted what I'd read Dan

Then just tried it I'm more worried about slow speeds but these tests show my shutters are all well within spec.

Ian

Ian

 

[Chan Tran]

For slow speed like 1/30 it's quite easy.