New to strobes, film ended up blank

[Gary L. Quay]

Hi all,
I was working with a model a couple weeks ago. I had originally intended to use my old movie floods, but my friendly salesman at Citizen's Photo asked my if I had an oven thermometer handy to see when she'd be cooked. So, I bought a strobe unit. I've always used natural light, but since I was using slower film indoors, I needed lots of light. I bought a Speedotron 2401 with two 102 heads. I bounced them off of umbrellas. I metered at the subject. The previous night I used a two boxes ofPolaroid B&W (3000 asa) on my hasselblad getting the exposure right, and did the division to arrive at the exposure for each of my films: Efke R25, Efke R50, Efke R100, Bergger 200, Tmax 400, and for 4x5: Arista 100, Ilford 125, and Efke PL50. The reason I used so many films is I'm trying to recreate the look of 1920's glamour photography, and I wanted to see which one had the best look for the job. All of the 4x5 was blank, even after pushing two stops. I got usable images out of the Tmax, and the Bergger after pushing. I got nothing useful out of the Efke roll film, even after pushing. I even calculated bellows factor for the 4x5.

A few things come to mind. 1) my math sucks. 2)My meter, a Polaris, has always metered properly for my Vivitar flashes, but I've never used it with strobes units. 3)I've used flash mostly with color films, not B&W. Assuming that the meter will read it at 18% gray, I have to adjust, but I thought I had worked it out with the Polaroid.

Any help would be greatly appreciated.

Thanks!
--Gary

[JW Dewdney]

IT seems to me that it could be any of a dozen (or more) things, Gary. If you're able to get successful results NOW - it's probably not your shutter or cable. But I can think of any number of scenarios that would do this (not pulling darkslides, having residual fixer in your dev tank, problem with the speedo, etc etc etc...). You'll have to do a little bit of detective work, unfortunately. If you can tell any of us exactly what you've proven DOES function properly, we can try to narrow it down... but without knowing specifics... well, it's kinda hard.

Jonathan

[Ole Tjugen]

Could the shutter sync be off?

You haven't put the little switch to "M", by any chance?

If not that, you could try a "manual sync": Open shutter, trigger strobes, close shutter. My first LF lens had no flash contact (broken off the shutter), but I still managed this:

[Helen Bach]

What exposure did you arrive at for the Polaroid, and what did you calculate for the various films?

Best,
Helen

[steve simmons]

Too many variables and not enough info as JW said but here are some suggestions.

Use a Polaroid film with a speed of 100. It will make the math easier.

Narrow your choices of films/

The films in the 20s may have been primarily orthochromatic in color response in which case nothing you used would match


steve simmons

[Nick_3536]

If the film is totally blank I'd lean away from math/metering issues and towards some other failure. Flash sync or you processed the wrong film?

[Helen Bach]

Were you using the roll film in a roll film back on the 4x5, or in your Hasselblad - ie did the failure happen with two different cameras, one of which had already worked with your setup?

Best,
Helen

[Mike Davis]

Do you remember the exposures that you used for the 25, 50, and 100 speed films? What is the power rating of the flash units?

One thing to remember with flash units is that you can't just keep decreasing(increasing) the shutter speed in a linear fashion to improve exposure. The flash is only there for a short time. In other words going from 1/125 to 1/60 won't get you another stop.

[Robert Oliver]

I would bet on the flash sync switch first (it should be on X, not M).

but then again, I would think it would be difficult to arrive at a correct exposure using a 3000 iso polaroid film to try to figure out exposure for 25 iso film. your dealing with a test film that is 7 stops different than one of the films you are using. I've never tried it, but I would guess you would have to power the strobe down as much as possible and still shoot at f90 to come anywhere near the correct exposure for iso 3000 film. depending on how far away your strobes are, you might even after to use ND filters to reduce output from your lights. the speedo packs are extremely efficient and powerful. (and fun to carry long distances) . If your at f90 with the 3000 iso, then your exposure for 25 iso should have been f8. you would want your polaroid film to match your intended film so you could also check your depth of field.

Get 100 speed polaroid and shoot 100 speed film. You have too many variables going on at once for even the most experienced studio shooter. remember the KISS rule. Keep it simple stupid (not that i'm calling you stupid, it's what my high school photo teacher taught us). with a flash meter that's anywhere near accurate, you shouldn't have to push film at all.

was the film blank or completely over exposed. if it's clear check the switch on the lens.

you could also test your flash meter by using manual guide number calcualations. The problem is coming up with accurate guide numbers for a given powerpack/head/box combination.

[Nick_3536]

What is the power rating of the flash units?
.

He mentioned a 2401 with two 102 heads. So depending on how he plugged in the heads it's either 200ws or 1200ws per head. So some combination in between. Even at 200ws he should have gotten some exposure.