Aaton LTR speed presets accuracy (is there really only ONE crystal speed)

[Aapo Lettinen]

Hi you all!

I made a crystal stabilized stroboscope light to easily test the accuracy of my cameras and for checking how well my different crystal sync designs work.

To test how well the strobo light works in first real world situation, I tested it on my Aaton LTR7.  The main reason for this was to determine if the camera has 24 or 25fps crystal speed because the crystal fps of it is not marked anywhere. From the previous owner's use I guessed it could be set to 25 and it definitely was 25fps accurately when I tested it.

But when I tested the other fps's of the camera they were not very accurate at all, I did not measure the difference but the 12fps and 16fps presets were maybe close to half a fps overspeed.

Is there only one crystal speed on the LTR's and all the other speeds are non-crystal RC oscillator generated with not very accurate results on them?  From the strobo test it surely looked like they would be not crystal because they were so much off whereas the 25fps was very accurate like it should be.

BTW if someone needs a crystal stabilized stroboscope light for testing movie cameras, I am manufacturing them and they are relatively affordable and very easy to use. Just DM me if needing one.

The best method I found was to shine the strobo through the viewfinder optics and look how it reflects from the mirror: extremely easy to see if it hits the mirror at exact sync OR if it is off, how much off it is (calculating how many seconds it takes for the camera to overrun or underrun the strobo exactly one frame. you can even see if it is over or under speed by inspecting the apparent rotation direction of the shutter under the strobo light)