Flash + filter question

Robin Usagani · May 10, 2011

Scenario one:
1/200 sec shutter
f/4 aperture
ETTL flash

Second scenario:
1/200 sec shutter
f/1.4
.9ND filter (3 stops)
ETTL flash

Are both flash power about equal?

camz · May 10, 2011

That's tough to say as your flash is in ETTL, assuming that your flash output is equal yes in theory they should be about equally exposed.

Robin Usagani · May 10, 2011

Ok so the only difference between the 2 shots are the DOF? One photo doesnt look more flashy as the other? Thanks camz.

camz · May 10, 2011

Yeah you have DOF and vignette(fall off) difference shooting wide open. If we're talking about stops, yes I think in theory they are equal.

Whatcha shooting?

Derrel · May 10, 2011

What happens at longer flash-to-subject distances, when the three f/stop loss of light transmission from the Neutral Density filter effectively maxes out the flash's power potential? What if you wish to add + (plus) flash compensation...the three f/stop loss of effective flash power will eliminate that capability much earlier (at closer distances) than when no ND filtration is being used.

Robin Usagani · May 10, 2011

Just bought ND filter and step up ring. I want to start shooting wide open with flash (off or on camera). Plus I want to do some motion blur shot in the middle of the day which is not possible a lot of times.

Robin Usagani · May 10, 2011

Ok derrel, let me rephrase my question, lets say both flashes are 1/4 power. One photo wont look more flashy?

camz · May 10, 2011

Schwettylens said:
Just bought ND filter and step up ring. I want to start shooting wide open with flash (off or on camera). Plus I want to do some motion blur shot in the middle of the day which is not possible a lot of times.

If you have high speed sync you should be able to shoot wide open without the use of an ND filter(Off camera or on camera flash). The motion blur is a little tougher during the middle of the day - the 3 stops can make a big difference.