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Shutter Speeds Inconsistent???

thefizz

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I have a shutter speed tester that I got from a guy on the large format forum some years ago and it works great when testing my RZ67 and Mamiya 7. I simply aim the lens at a strong light while holding the device behind the camera with the door open or film back detached. Most of the shutter speeds are pretty accurate with the 1/250 and 1/500 being about a third stop slow which I know to allow for when photographing.

Recently I got a Nikon FE2 and an FM2 and decided to test the shutter speeds. The readings are very inconsistent. For example, every time I test the 1/125 setting I get anywhere between roughly 1/60 to 1/125 which is a full stop difference.

Does anyone know why this is happening? Is the shutter tester not able to read the times on these 35mm cameras as well as it can on my medium format cameras? Shutter in the lens versus in the camera?
 
The light must be sufficiently bright. The shutter-speed tester that Thomas Tomosy was producing years ago has a BIAS knob for calibrating the tester to the light source. Are you putting the sensor in the middle of the curtain so that light will not hit it at an angle? Assuming the light is bright enough and your cal is correct and sensor is centred, perhaps both cameras are inconsistent. Can you try a third camera?
 
Perhaps the tester is designed for leaf shutters, not focal plane shutters.
 
To measure focal plane shutters, ideally two sensors are required, to measure both curtains. It is possible to use a single sensor & move it from right to left, or top to bottom, but that is a bit of a faff.

The OP has not described their shutter tester or provided any photos, so it could be sometimes he is measuring first curtain and other times second curtain? Just a thought.

There are many homebrew shutter testers out there, I'm not going to get into the debate of which is best or pass comment on any of them.

Will say that my own tester, look for the 'build a cheap shutter tester that works' in this section works perfectly with 35mm focal plane shutters. I started the post to help people build a cheap tester (that works).
 

Can you post some photos of this tester?
How many sensors does it have?
Are you holding the device in exactly the same place each time?
 
Matt is correct, I checked old correspondence with the guy who made it and it is indeed only suitable for leaf shutters.
 
thefizz said:
Matt is correct, I checked old correspondence with the guy who made it and it is indeed only suitable for leaf shutters.
Click to expand...

You might want to check out these threads about focal plane shutter testers:

Build a shutter tester for Focal Plane shutters - Cheap, Easy & it Works

Hello Everybody, #1 There are many home-brew shutter testers out there, some use audio to try to detect the speed, others use an Arduino and one sensor (so will not work correctly) and there are better ones that use two sensors. A problem seems to be a misunderstanding of how a focal plane...
www.photrio.com

Building A Professional Grade Shutter Tester

While gearing up to make a shutter tester in this thread (https://www.photrio.com/forum/threads/build-a-shutter-tester-for-focal-plane-shutters-cheap-easy-it-works.197756/page-5#post-2663014) I came across all the schematics, BOMs, Gerber files and STL files to make a professional grade shutter...
www.photrio.com
 
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