How do you know how much power to add to a flash in manual mode?

jonneymendoza

jonneymendoza

jonneymendoza

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Hi.

as the title states. How do you?

Do yo simply take a few test shots and guess or do you know a genuine way to calculate teh correct flash power to apply to a given scene to make sure the flash does not overexpose the subject or underexpose?

Thanks
 
it depends on too many variables, just try and remember that the shutter effects ambient light and the aperture effects flash light, its a little trial and error .
 
You can use a light meter if you must, but to be honest trial and error is quicker anyway. If you absolutely need to get the flash perfect from the get go then either shoot with headroom either way so that you know you have a workable setup when you get to post, or shoot with an ettl flash.
 
You can typically get the right flash exposure within 3 shots.

1. Guess what you expect it to be.
2. Tweak the flash power if the first shot is under/overexposed.
3. Tweak a bit more to get it perfect.

Done!
 
Ksanti said:
You can use a light meter if you must, but to be honest trial and error is quicker anyway.
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I've very little experience in this areaso this is a genuine question.... but how is trial and error quicker. Surely the point of a light meter is "pop, read the settings, put them into the camera".... or am I missing something here? :confused::confused:
 
I imagine they mean it from the point of view that you have to get the meter, go and test the lighting for the area, possibly take multiple readings to make sure it's correct, then go back and dial it in. In this time you could have fired off 2 or 3 shots.
 
If you use the Sekonic L-758DR and your triggers fire using 433 MHz, you can simply take an incident reading from your subject and press a button on your light meter and fire the strobe. You will get an instant reading for correct exposure. Yongnuo 622 Pocket wizards will work perfectly with this system.

A light meter should be one of the first purchases you make when you are a photographer using flashes. The workflow is rapid, the guess work is gone.. You nail exposure every time. Chimping is far more time consuming. The other benefit of having a meter is knowing the precise point of 18% grey. 2.5 stop above correct exposure is white, and 4 stops below is black. This will allow you to completely take control of the light in your image, and have detail in the shadows.
 
-|ScottFree|- said:
If you use the Sekonic L-758DR and your triggers fire using 433 MHz, you can simply take an incident reading from your subject and press a button on your light meter and fire the strobe. You will get an instant reading for correct exposure. Yongnuo 622 Pocket wizards will work perfectly with this system.

A light meter should be one of the first purchases you make when you are a photographer using flashes. The workflow is rapid, the guess work is gone.. You nail exposure every time. Chimping is far more time consuming. The other benefit of having a meter is knowing the precise point of 18% grey. 2.5 stop above correct exposure is white, and 4 stops below is black. This will allow you to completely take control of the light in your image, and have detail in the shadows.
Click to expand...

That cost same amount as a 600ex canon flash!
 
Trial and error is definitely by far the quicker option for on camera flash as you can immediately flick between settings between frames. For off camera flash there's less in it but tbh you can usually see in an image and in a histogram how much extra light you need so the most it's ever taken me is three frames to get the exposure exactly where I want it.
 
With my setup (7D, Yongnuo 622c + Yongnuo 565/568) I don't even have to leave the spot where I'm taking photos from because I can manually adjust flash output for three different groups from the in camera menu.

I can certainly see the point of a light meter and would like to own something like the one ScottFree mentioned but I would much rather spend that cash on more flashes, modifiers, lenses etc.
 
Why spend All that cash on a lightmeter...Silly, unless you be a Pro.
You be using Digital, so it cost you NOTHING to take three shots..One shot at 1/200 or 1/250 at f8 the other at f11 should give you what you want. If it is a bit darker then go down to 1/125 or 1/60 at same appertures. Easy Peasy..
 
RussD said:
Why spend All that cash on a lightmeter...Silly, unless you be a Pro.
You be using Digital, so it cost you NOTHING to take three shots..One shot at 1/200 or 1/250 at f8 the other at f11 should give you what you want. If it is a bit darker then go down to 1/125 or 1/60 at same appertures. Easy Peasy..
Click to expand...

It can cost time taking 3 shots and readjusting your flashes or camera each time
 
On my 430ex2, the power settings goes from 1/64, 1/32 .....1/1 being the highest.

So my question is, how do i get the relivent figure about with this formulae: GN / metres = aperture

say i know wroughly the distance between flash and subject, say 10m to keep it simple and apparture is f10. what is the formulae?

10/10(distance / apparture) = 1? and 1 being 1/1 to dial in my flash?

say if its f 10/5 = 0.5 im guessing 1/50 on my flash settings?

Also: just found out that some flashes have a build in light meter!

 
I think you will automatically get a feel for it after some practice, I am brand new to taking any photo's with a dslr and have just purchased a manual flash, even I can get the power right after just a couple of shots and very little practice, well no practice really, take shot, too dark, adjust flash, take another, nearly there, one more click of power and it's fine.
 
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