Paul C. Buff, Inc. Technical Forum

So trying to wrap my head around this....Just got my new Einsteins and was doing some tests before taking them on location (we do kids dance studio photos) We have been using Speedotron black line for years so I am new the the Paul C Buff line of lights. Anyway I set up two einsteins with the 86 inch soft silver PLM umbrellas (I am very impressed with the quality of everthing). We usually shoot the speedtrons at F16 @200th metered about 10 feet away (canon 30d's) So set up the Einsteins the same and I shot a McBeth card and a couple of my assistants 5 year old and noticed they looked a little hot...backed the lights off to 11.5 and it looked right... Puzzled I set up the speedotrons (102s and a 2405 pack) and did the same test ...at F16 the matched the Einsteins at F11.5. (granted the speedotrons are pretty old and have been thru several thousand flash cycles) Took both tests into photoshop and compared numbers and the Einsteins @ F11.5 were pretty equal to the Speedos @ F16...
I don't get what is going on..both were metered the same...I thought light was light but this doesn't seem to be the case..All I can think is it has something to due with the duration of the two brands and how the meter (minolta) is reading it....???
Any advice/input would be appreciated. What is great about the Einsteins is that I can now go back to 1/250th and freeze the
jump shots again something I wasn't able to do with the speedos.

Thanks
Mark

Part of it could be the modifiers used. That was not really clear. I see you use PLM's, but not sure if those were in use before.

Part of it could be the flash duration. It is possible for long flash duration strobe pops to be truncated by the shutter speed. This will result in a lower than expect brightness in the image (this can even happen with flagship speedlights). With Einstein's shorter flash duration, it would not be truncated by the shutter. Not knowing all the specifics, all I can say is this is very plausible.

You can try shooting at 1/100 of a second and compare. With the longer exposure time, additional time is allowed for the slower flash to reach the sensor.

You haven't given enough info to really assess the situation.

First, were you using the same modifiers on both the Speedo and the Einsteins? You would have to use the same modifiers on both lights in order to make any valid comparison.

Also it sounds like you were using two Einsteins, but one Speedo head?

If you are a saying the Einsteins, when metered at f 11 +5/10 produced the same exposure as the Speedo when metered at f16, TECH is correct. 2400Ws Speedos produce very slow flash durations - on the order of 1/150 second t.1. So it's likely your shutter speed was faster than the Speedo flash duration, and that your flash meter was set to a longer exposure time than your camera?

In this situation, the Speedo would meter higher exposure than your camera actually receives, because your shutter closes before the Speedo has put out all its power.

Assuming you are indoors, I would suggest setting the camera and the meter at 1/60 second. Then repeat the test.

As for for stopping action on the jump shots, you are assuming the camera shutter speed determines the action stopping. This is incorrect . . . it's the flash duration that stops action. With the Einsteins fast flash duration, you will find the action stopping the same with a 1/60 shutter speed as it is at 1/250 shutter speed (unless you are outdoors with a huge amount of sunlight).

In brief, it is the Speedo's slow flash duration that is causing motion blur, regardless of shutter speed.

I could write page after page about this - this is a relationship a lot of photographers don't understand. Check out our web info at http://www.paulcbuff.com/sfe-sync.php and at http://www.paulcbuff.com/sfe.php for more info.