Shutter Speed Testing

DWThomas said:

Mayhaps it's my ancient electronics experience burping up, but I would take the width at the 50% mark as a shutter speed

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I concur. The delta t between the 50% amplitude points. For really fast speeds when the rise and fall times of the edges are comparable to the delta t this should still work to a first order approximation.

wombat2go said:

So next week I will take some time to set up to test the next Sekor lens a bit more rigorously.. I will take photos of my test setup and waveforms, check variation over aperture, and with jeff's permission, post the results in this thread.

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Don't worry about permission from me. I'm happy to see all the different discussions that are branching off on this subject. I'm enjoying it all, learning a lot, and getting some fresh ideas.

PeterB said:

I concur. The delta t between the 50% amplitude points. For really fast speeds when the rise and fall times of the edges are comparable to the delta t this should still work to a first order approximation.

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Most shutters have fixed blade or blind speeds.
Most shutter efficiencies vary with aperture of the lens.
If you have a spread sheet of times like in this thread, then you need to know the max and min aperture and the aperture of the test sequence.

The times can seem way off but may still be close to factory tolerances.

Most normal between the lens shutters have

No more than 50% efficiency wide open at shortest speed
About 90% efficiency at smallest aperture at same shortest speed

The big sin is fixing something that is not broke.

This may be of interest; is is an offer that I received about a year ago, from Vasile Florin (shuttertester@gmail.com) :




I am offering a new shutter tester at a special Christmas price of $99.99 USD
What you get:

- 1 shutter tester and EV tester capable of measuring speeds up to 1/8000th of a second and curtain speeds.

- A PDF English manual with detailed information on how to use the shutter tester (sent at the PayPal email address).

- 12 month warranty!

About the product:

- The shutter testers are built by me. Every shutter tester will be tested before shipping.

- Tests shutter speeds up to 1/8000.

- Tests curtain speeds up to 1/18000.

- Light source included.

- Cable sensor for cameras with bellows and TLR cameras included.

- Dual power (battery or power adapter). Needs a 9 volt battery (NOT included) or a 9V DC power adapter with a 2.1mm DC jack (Due to the different grid voltages and various plug types from all over the world the power adapter is NOT included!).

- Each connector has a different type of plug (Cable tester, curtain tester, light source and power adapter connector) to avoid accidents.

- The tester can measure speeds over 30 seconds.

- Has two sets of curtain speed photocells so you can test both vertical focal plane shutters and horizontal ones.

I should have made clear, in the above message, that I have no connection to the vendor, other than having bought the meter from him, as a gift for a friend.
I also ask the moderators to review my previous post, and I hope that I haven't crossed any lines of propriety.