Two New Toys ... and some Questions

[jtsmith]

Originally Posted by R_Fredrick_Smith

It also depends very much on the shutter speed. Dean Collins went into great details about this years ago with his Chromazones series. Essentially you can alter the color not only by the gels you use, but by the shutter. So in this case, we light the model with a flash, use an fstop needed for that and then vary the shutter speed to get the background color lighter or darker.

Cheers,
rfs

I am sorry but I can't let this statement confuse people. Unless the background light that has a gel is a continues light, as in tungsten or natural light, changing the shutter speed on a strobe with a gel is not going to control if it's lighter or darker.

JT

[eoym]

Originally Posted by Steve_Buchanan

Ok, I'll wade in here...
3. Shutter speed WILL make some difference if your exposure even when using strobes when at the high end of the sync speed. Alien Bees have a relatively long flash duration so adjusting your sync from say 125 to 200 will show a noticable effect. It won't be the 2/3 stop that it would be with continuous light but it will make a diff. Previous poster correct when dealing with lower shutter speeds. Going from 8 to 60 probably will have no noticable effect.

FWIW

Steve

Ok, I looked up the specs on an AB800 and found that the flash duration is 1/3200th of a second. Any shutter speed setting slower then that will have ZERO effect on the exposure this flash is providing.

Changing shutter speeds will ONLY effect how much ambient light records.
For the sake of agument, let's say there was no ambient light at all, completely dark studio, you could set your shutter speed at anything less the 1/3200th of a second and there would be NO difference in exposure. Hell, you could leave the shutter open and go take a lunch break!
:-)
The exposure was made, and completed, at 1/3200th of a second. And in a dark studio....there is no more, or no less, light left after that.....it's done.

[CatCynic]

Originally Posted by eoym

Ok, I looked up the specs on an AB800 and found that the flash duration is 1/3200th of a second. Any shutter speed setting slower then that will have ZERO effect on the exposure this flash is providing.

Changing shutter speeds will ONLY effect how much ambient light records.
For the sake of agument, let's say there was no ambient light at all, completely dark studio, you could set your shutter speed at anything less the 1/3200th of a second and there would be NO difference in exposure. Hell, you could leave the shutter open and go take a lunch break!
:-)
The exposure was made, and completed, at 1/3200th of a second. And in a dark studio....there is no more, or no less, light left after that.....it's done.

Not quite right! At any shutter speed SLOWER THAN THE SYNC SPEED, sure, no problem. If you are at 1/2000 second (faster than the sync speed of any camera I know) then you will see a difference - there will be a brightly lit bar on the image, and the rest will be black. The reason is that the sync speed of the camera is the fastest shutter speed at which the sensor (or film) is completely exposed. Anything faster, and the shutter curtains both move at the same time (the distance between them controls the shutter speed). The bright bar will be the portion of the sensor which was uncovered when the flash went off.

BTW: I have trouble believing that the ABs are 1/3200 second - that's extremely fast. I suspect that they are rather slower than that - more like 1/700-1/1500.

[eoym]

Originally Posted by CatCynic

Not quite right! At any shutter speed SLOWER THAN THE SYNC SPEED, sure, no problem. If you are at 1/2000 second (faster than the sync speed of any camera I know) then you will see a difference - there will be a brightly lit bar on the image, and the rest will be black. The reason is that the sync speed of the camera is the fastest shutter speed at which the sensor (or film) is completely exposed. Anything faster, and the shutter curtains both move at the same time (the distance between them controls the shutter speed). The bright bar will be the portion of the sensor which was uncovered when the flash went off.

BTW: I have trouble believing that the ABs are 1/3200 second - that's extremely fast. I suspect that they are rather slower than that - more like 1/700-1/1500.

I don't even know what to say in response to this.
What sense does it make to explain what would happen at synch speeds of 1/2000 second? I'm pretty sure that Lee was looking to achieve something other then a "brightly lit bar on the image". Most likely he was looking to expose the entire frame.
I'm also pretty sure that Lee understands flash synch and I didn't feel it necessary to point that out to him.

Also, how on earth would you know the flash duration of ABs? The specs from the manufacturer are wrong?....and you know better then they?

[Steve_Buchanan]

I don't have any technical experience with the Alien Bees but I do know through experience that changing your shutterspeed from 125 to 200 will have an effect. I did it yesterday. I use Bowens/Calumet strobes and they're not known for their short flash duration. Maybe it's just my strobes - but I would encourage everyone to just try it. Shoot your camera bag and see what happens.

[eoym]

Originally Posted by Steve_Buchanan

I don't have any technical experience with the Alien Bees but I do know through experience that changing your shutterspeed from 125 to 200 will have an effect. I did it yesterday. I use Bowens/Calumet strobes and they're not known for their short flash duration. Maybe it's just my strobes - but I would encourage everyone to just try it. Shoot your camera bag and see what happens.

I looked up the specs on a Bowens strobe, I just picked one of their lower priced units as I don't know which light you may have.
For the sake of this discussion the flash duration on a "Bowens Esprit Gemini AC/DC Monolight - 500" is 1/700th of a second @ full power.

So at any shutter speed less then that the amount of light that the flash puts out will be the same...and the exposure that the flash is providing will be the same.

If your seeing differences in exposure by changing shutter speed 1/125th to 1/200th then what you're seeing is the AMBIENT light affecting the exposure...the flash gave ALL of it's light at 1/700th.

In an absolutely dark studio, no ambient light whatsoever, there would be NO difference in exposure by changing shutter speed from 125th to 200th.
In fact, you'd see no difference by changing shutter speed from 1/700th (assuming you could synch at the speed) all the way down to as slow as you could go.

Try it out on your camera bag, as you suggested. Make sure there is no ambient light...make your studio as dark as possible. Now shoot your camera bag with one of your strobes and start out using the fastest synch speed your camer allows. And take photos with different (slower) shutter speeds ......go all the way down to a full second or two.
You'll see no difference, provided there is no ambient light.

[FotoTejas]

Dean and crew,

Thanks for all the input. I'll be in the studio again today setting up a "Christmas decorations" set for a bunch of family Christmas card shoots this week, so I'll play with all your suggestions.

I suppose it is common sense that I shouldn't have "cranked" the B-800s. Common sense isn't my strong suit!

Dean, yes, I do understand flash sync! LOL I've just never shot with gels. Maybe I'll start with just one of the lights, too. I was just trying to get good coverage on the BG.

Everyone have a good weekend.

[FotoTejas]

In case anyone is interested in the "Great Gel Experiment," the results are posted below.

My model scheduled for this morning flaked-out, with a typical college girl excuse. This time, her "ride and escort" stayed out too late last night and couldn't come to the shoot. She informed me of this fact with an email (not telephone, though she has my mobile number), approximately 45 minutes before the scheduled start of our shoot.

Luckily, the always-reliable Madera was able to substitute for me on short notice. Her posing is a bit wooden, but at least I know that I can count on her.

The main light was a B-1600, metered to f16 at Madera's cheek. It is set at camera-left (obviously), at about sixty degrees from the line of the shot. It is gridded at 20-degrees and fitted with barn doors, to keep its light completely off the background.

The background lights are two B-800s, fitted with the same "dark green" gel used in the initial post and aimed at the white wall of my studio. Each was set at identical power level for each shot, at the settings indicated in the sample shots.

[eoym]

Excellent Lee! Thanks for sharing this little experiment.
The only things is you didn't tell us what shutter speed you used!!??
;-)

Oh, and that Madera sure is a doll isn't she?

[FotoTejas]

Dean,

Yeah, Madera is a really solid gal.

Shutter speed was 1/125. My camera revolted when I tried to set it at 1/2000.

As an aside, the f5.6 is the closest to the actual color of the gel.