Off Camera Flash...

[BuS_RiDeR]

Picked up this little tidbit from my local camera club's Facebook group.... To help figure out what Aperture to use when using OCF. (Your shutter will be set to your camera's sync speed.)

I thought I'd share... and I have a question...

f = G ÷ d
d = G ÷ f stop

f = aperture
d = distance from flash to subject
G= flash’s Guide Number

My question... What if you are using 2 flashes? Do you divide the result by 2??? Average it out to compensate for different flash to subject ratios???

 

[tirediron]

My question... What if you are using 2 flashes?

Buy a flash meter!



You can, with some experience estimate exposure for multiple flashes, but if you're into that level of lighting, you really should treat yourself to the single most useful tool in the lighting arsenal.

 

[camz]

In theory if you add one flash to the already existing flash you will add an extra stop. Considering that its triggering with the same output power at the same exact location. I do that to save on battery where I have two flashes mounted on a lightstick where I dial them both at half power.

So as far as the power with two flashes is concern, yes I divide by two to equal the same exposure of one flash. If you're doubling the flash where a single flash is equal to the right exposure, you'll have to multiply the flash power by two.

 

[tirediron]

In theory if you add one flash to the already existing flash you will add an extra stop....

True, but in most cases you're not going to use two flashes in the same location.

 

[camz]

In theory if you add one flash to the already existing flash you will add an extra stop....

True, but in most cases you're not going to use two flashes in the same location.

From what I've seen with other photographer's shooting style probably not. I do use this alot during reception for my main light.

 

[BuS_RiDeR]

Buy a flash meter!

No can do... I am out of work and living on medical disability insurance. I am saving my pennies for a meter... But I want a macro lens or extension tubes before that...

I am not too proud to accept donations though.

You can, with some experience estimate exposure for multiple flashes, but if you're into that level of lighting, you really should treat yourself to the single most useful tool in the lighting arsenal.

Thanks for the input... But part of my medical issues involve memory problems... Therefor, I prefer not to put too much faith in experience... Especially new experiences. I have less problems with stuff I already know... At least it seems that way.

My background/history.... The Liptonian Institute - Mark, Linda, and Sam: A cancer survivor's story/diary. Last updated October 7th, 2011

 

[BuS_RiDeR]

Thanks for your input as well Camz.

 

[IgsEMT]

buy a grey-card, they have some with instructions on metering, zone system and white balance. Read those and use it for metering. Average 8x10to 8.5-11 card would cost no more then $10.
Here's the one I have Delta 1 Gray Card 8x10" (1) 22030 B&H Photo Video
I took it, scanned the back and printed it smaller 2 copied. Then cut the card into 2 while taping the printed material on the back.
One card is in the camera back and I use it on-location and second one in-studio.

 

[tirediron]

No can do... I am out of work and living on medical disability insurance. I am saving my pennies for a meter... But I want a macro lens or extension tubes before that...

Check out eBay and Craig's List for used, analogue meters. They come up fairly often, and even high-end meters (Luna-Pro F, and similar) can be had very cheaply. They might not look as sexy as a brand-new Sekonic 700-series, but they will work just fine!

IgsEMT's idea of using a grey card is a good one; not quite as flexible as having a meter, but will get you into the ball-park a lot more quickly.

 

[bazooka]

Or you could just take a shot and look at it on the histogram. That's what I do and it works well, combined with RAW processing to compensate for some error.

 

[Village Idiot]

You can find old used meters that don't cost $300. The problem is without memorizing experience or having a device to meter, it becomes almost purely trial and error. If you're using two flashes in different positions, they could end up far enough apart that they don't affect the exposure of each othe,r or they could be close enough to overlap where they do affect the exposure of each other, or they could be close enough together to cause the overall light to go up by one stop.

You also have to deal with zoom in your equation if you're using speedlights with zoom head heads.

 

[BuS_RiDeR]

Or you could just take a shot and look at it on the histogram. That's what I do and it works well, combined with RAW processing to compensate for some error.

This is a thought... But I don't understand how to read the histogram.

 

[BuS_RiDeR]

buy a grey-card...

I can probably swing 6$.

 

[BuS_RiDeR]

Check out eBay and Craig's List for used...

I agree this is a good idea. However, the government pays me under $800 a month... Toss in my mortgage payments, car payments, groceries, taxes and all that good stuff... And well... I am saving my pennies (literally) but it will take a while.

 

[BuS_RiDeR]

Thanks for the input guys/girls.

Looks like trial and error it is; at least until I can afford a meter...