Best way to test wireless flash trigger's max sync speed?

[mweintraub]

I have a new trigger system that I like because I get to control the power on the Streaklight 360 bare bulb flashes, but I'm not sure if it can handle the faster sync speeds of medium format leaf shutter lenses. If these don't handle the higher speeds, I found that the Impact FlashSync 16 / SMDV FlashWave III system has been reviewed as being able to sync high on the Fuji X100 bodies, so that might be my go to if these other ones don't.

I was thinking of shooting a gray card in either inside at max speed, but I wonder if shooting outside would be better. Something where the background is a lot brighter so the gray card is shadowed and very underexposed by ambient.

Thoughts on which would give me better results?

 

[Luckless]

I have a new to me leaf shutter that I'm going to have to test for flash work here, so should be a useful thread for me to follow.

My key worries are:
- Flash trigger timing at very low speeds, as to whether or not the flash is still peaking within the 1/500th,
- Flash duration, whether or not the majority of the flash power is still going to fall within the shutter open time, or will some light be cut off before/after the shutter's cycle. (I need to double check the spec sheets for flash time duration.)

My plan to test with is going to be to rig up some kind of an adaptor out of an extension tube to project onto one of my digital cameras that I set in bulb mode. Aim that at a target where all the exposure is going to be from the flash, then when I trip the leaf shutter (while the digital is sitting open in bulb mode) I should be getting a fairly consistent exposure whether using 1s on the leaf shutter or 1/500th.

If I see an exposure drop at any speed, then I will have a little more work to do to try and figure out where the issue is. However if I'm getting the same flash exposure out of the 1/500th as I am out of the 1 second shutter speed on the leaf spring, then I know I'm good to go.

 

[mweintraub]

My plan to test with is going to be to rig up some kind of an adaptor out of an extension tube to project onto one of my digital cameras that I set in bulb mode. Aim that at a target where all the exposure is going to be from the flash, then when I trip the leaf shutter (while the digital is sitting open in bulb mode) I should be getting a fairly consistent exposure whether using 1s on the leaf shutter or 1/500th.

If I see an exposure drop at any speed, then I will have a little more work to do to try and figure out where the issue is. However if I'm getting the same flash exposure out of the 1/500th as I am out of the 1 second shutter speed on the leaf spring, then I know I'm good to go.

I'm thinking of doing the same with one of my lenses and a adapter too. Since the DSLR doesn't trigger the LS internally, I was thinking of using dental floss to pull the aperture thingy to trip it.

As fast as testing the sync, you could baseline with a wired cable.

 

[mweintraub]

My plan to test with is going to be to rig up some kind of an adaptor out of an extension tube to project onto one of my digital cameras that I set in bulb mode.

I got it to work. I had a hard time months ago to get a Mamiya L/S to work, but I have a Pentax 6x7 90mm L/S now and it has the little U/S switch that makes it work. This is what I did.

I have a Pentax 6x7 to Nikon F adapter so I used that with he 90mm. I switched the U/S switch to S and then cocked it. This allowed me to stop down the lens and close the L/S blades by moving the aperture bar on the back (Not sure what to call it.

- I took a piece of dental floss and "U-ed" it around the aperture bar on the back and mounted the adapter. Because of the direction of the twist, it engaged the aperture and L/S blades.
- Then mount the adapter on the body. At this point, the viewfinder is black because the L/S blades are blocking all light.
- Attach PC Sync cable to flash transmitter
- Attach shutter release plunger to lens (needed to trigger L/S on lens)
- Set camera to 1s shutter speed
- Set L/S speed to 1/30s
- Set flash power
- Press camera shutter, then press plunger to trigger L/S in lens. SUCCESS!

- Cock lens L/S
- Change lens speed to 1/500s
- Repeat = SUCCESS!

It's out of focus, but the brightness is the same between the 1/30s and 1/500s speeds, so there is no loss of light with the triggers I have. Awesome.

 

[Luckless]

Very awesome. Did you test it at the highest and lowest setting of the flash? Shouldn't matter, but always better to benchmark tools when you have a chance than get surprised in the field when you're relying on it.

I still need to rig a test up for mine sometime in the next week or so, but luckily the TLR lens I have puts all the controls right there on the front, so at least I don't have to rig anything up with regards to that.

 

[mweintraub]

I did not. Good idea because of flash duration. I was more curious than wanting to do a full test. I was sitting on the floor and wanted to get up.