PDA

View Full Version : Non TTL flash settings - how do you know?



CaliGal
09-27-2008, 09:06 AM
I'm just getting into using studio type strobes and off camera flash (ya I know all about strobist.com and other resources one can search for online).

Short of using some kind of meter to measure the intensity of flash(es) you are producing, how does one know what settings to use (in full manual)? I can guess and probably get pretty close - or experiment to find what works is always an option too...I just don't want to make a lot of big mistakes, especially if I start getting in "model volunteers" to help me learn this stuff.

The variables are so many - light intensity, shutter speed, aperture, ISO, distance - it all seems like a bit of a guess.

If a flash meter is absolutely necessary, what's the very least expensive option to start out with?

D Thompson
09-27-2008, 09:53 AM
Without a meter you are basically just trying settings until you get something you like. In a studio situation you control the light. As far as the settings you usually want your ISO to the lowest (100). I usually go for a shutter of 1/80-1/125th at f9-f10. Usually my main light is metered for f8 and the fill at f5.6 which combined will come in around f9-f10 or so. Distance of the flash/strobe to subject will have an effect. Move it closer and you need to dial the power of the flash/strobe down a bit to compensate and keep the same settings. As long as you keep the flash/strobe the same distance from the subject you should get the same result if you move the flash to a different spot.

I'd highly recommend getting a light meter. This one is one of the least expensive that works very well that I've found.

http://www.bhphotovideo.com/c/product/368226-REG/Sekonic_401309_L_308S_Flashmate_Light_Meter.html

Hope this helps some.

AlexMonro
09-28-2008, 06:10 AM
This is what the guide number quoted for the flash is for. It's a measure of the light intensity of the flash, and is usually quoted in terms of a distance, in feet or metres, at a given ISO. To calculate the aperture to use, divide the guide number by the distance from the camera to the subject, this gives you the f/number at the rated ISO.

If you want to use off camera flash, you need to add the distance from the flash to the subject and from the subject to camera and divide by two, and divide that into the guide number. To use a different ISO, add or subtract an f/stop for each doubling or halving of the ISO.

Assuming you're not trying to fill in with ambient light, i.e. the ambient light is very dim, shutter speed is irrelevant as long as it's slower than the sync speed.

If you do want to fill in ambient lighting, or use multiple flashes, get a meter.

CaliGal
09-28-2008, 06:34 AM
Thanks for the reply. In the reading I've been doing, there seem to be two schools of thought on metering.
1. Use on for "correct" results on your first try.
2. Don't. You can accomplish the same thing with your in camera metering, histograms, and "chimping". (Alternative to this is to shoot tethered - or maybe use the HDMI out on my A700 to review shots?)

I thought I's at least try it both ways to see what works best for me.... especially since I may be using anywhere from 1-6 flashes at any given time. time to check out the meter you've noted, and maybe some other "used" ones, as long as they do flash metering.

D Thompson
09-28-2008, 10:35 AM
Thanks for the reply. In the reading I've been doing, there seem to be two schools of thought on metering.
1. Use on for "correct" results on your first try.
2. Don't. You can accomplish the same thing with your in camera metering, histograms, and "chimping". (Alternative to this is to shoot tethered - or maybe use the HDMI out on my A700 to review shots?)

I thought I's at least try it both ways to see what works best for me.... especially since I may be using anywhere from 1-6 flashes at any given time. time to check out the meter you've noted, and maybe some other "used" ones, as long as they do flash metering.

If you're going to be using that many flashes I wouldn't even consider the chimping method. There may be cheaper meters and you may find one used somewhere. That one works well for me. Good luck in whichever method you decide to use.

Rhys
09-28-2008, 05:15 PM
With studio flashes, the strobe power is given in WS - Watt Seconds. With pocket flashes they're given as Guide Numbers. There is no conversion between the two - they're utterly different measures.

You do need a flash meter. Oddly enough I have an old flash meter that I might be willing to part with for the right amount of money.

If it's a mix of flash types then without a meter the computation will be horrendous. If you mix automatic and manual flashes then even metering might not be all that accurate.