Can you measure ambient light with your camera?

dubcat

dubcat

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Hi, I am working my way through Strobist's Lighting 101 and am currently on the page about balancing ambient light (http://strobist.blogspot.com/2006/03/lighting-101-balancing-flash-and.html).

David talks about ambient light generally being about 1/60th at f/4 at ASA 400. Rather than working with this rule of thumb can you not simply use your camera by setting ASA 400 at 1/60th in Av mode and seeing what the camera recommends for aperture when you half press the shutter release? It may well come back with f/4 as David says but if it is lighter or darker in the room you are in then the camera will tell you right?

Would you need to focus on a grey card to use the camerea as a light meter in this way? Seems a lot cheaper than buying a light meter.

Or am i getting this all wrong?

Cheers,
Dub
 
I think you're getting it right, but your Av settings are a bit adrift - you set the f/number and the camera does the shutter speed to match the ambient.

That's all there is to it in theory, but of course you might want to adjust the flash/ambient balance that the camera then makes. That's easy enough too, by various means.
 
Ah i got my Tv and Av mixed up :) So why is David Strobist using that rule of thumb guide when he has a light meter in his camera?

By the way - do you need to have a grey card to use it in this way or can you just meter off anything in the scene?
 
dubcat said:
Ah i got my Tv and Av mixed up :) So why is David Strobist using that rule of thumb guide when he has a light meter in his camera?

By the way - do you need to have a grey card to use it in this way or can you just meter off anything in the scene?
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he's not, you misread ;)

erm meter off anything grey, best solution is to take a test shot on digi tbh, then dial it down how much you want in manual test shot again, then build up the flash

remember test shots are free

as you get more used to it you skip stages and take less tests ;)
 
Ambient exposure cannot be measured in the way you suggest. Perhaps he's in a consistent environment and knows that in the location he's in the ambient is measured at the exposure suggested.

When using flash the camera is best used in M. To set the ambient exposure of a general scene, dial the required Av and ISO and adjust the SS till the meter is in the centre. If your SS is more than the sync speed you need to use a smaller aperture (larger fstop number)

Once you dial that in, your flash should light your subject and you will generally get a nicely exposed background.

To increase/decrease the background exposure, the SS controls that. Av is controlled by the flash power (you can use a meter to measure this if your flash is in Manual). If the flash is in ETTL, the Av controls the power of the flash.
 
EOS_JD said:
Ambient exposure cannot be measured in the way you suggest. Perhaps he's in a consistent environment and knows that in the location he's in the ambient is measured at the exposure suggested.

When using flash the camera is best used in M. To set the ambient exposure of a general scene, dial the required Av and ISO and adjust the SS till the meter is in the centre. If your SS is more than the sync speed you need to use a smaller aperture (larger fstop number)

Once you dial that in, your flash should light your subject and you will generally get a nicely exposed background.

To increase/decrease the background exposure, the SS controls that. Av is controlled by the flash power (you can use a meter to measure this if your flash is in Manual). If the flash is in ETTL, the Av controls the power of the flash.
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Yeah, he's just talking about what the light level might be in the average room.

That's one way of doing it, but I hardly ever use Manual. The main benefit of manual is that it locks the settings, but in a typical indoor situation I find the ambient light varies quite a lot around the room and using Av the camera will track that automatically, whereas in manual you have to reset it each time, or at least double check.

I do it like this, specifically with Canon - other brands may operate differently. Set Av and f/number, flash on E-TTL, check that the shutter speed isn't too long for hopeless ambient blur, adjust if necessary, and shoot.

See what it looks like. It's usually pretty good TBH, but if the flash is too bright, turn it down with minus compensation on the gun. If the background is too dark, add plus compensation on the camera. And vice versa.

If there's time to get things just right, I will gel the flash to match the ambient colour and adjust white balance, maybe use bounce/fill or a diffuser of some sort, but the method of exposure setting remains the same.

At the end of the day though it's just a method of working. Whichever way works for you, the end result should be the same.
 
HoppyUK said:
Yeah, he's just talking about what the light level might be in the average room.

That's one way of doing it, but I hardly ever use Manual. The main benefit of manual is that it locks the settings, but in a typical indoor situation I find the ambient light varies quite a lot around the room and using Av the camera will track that automatically, whereas in manual you have to reset it each time, or at least double check.

I do it like this, specifically with Canon - other brands may operate differently. Set Av and f/number, flash on E-TTL, check that the shutter speed isn't too long for hopeless ambient blur, adjust if necessary, and shoot.

See what it looks like. It's usually pretty good TBH, but if the flash is too bright, turn it down with minus compensation on the gun. If the background is too dark, add plus compensation on the camera. And vice versa.

If there's time to get things just right, I will gel the flash to match the ambient colour and adjust white balance, maybe use bounce/fill or a diffuser of some sort, but the method of exposure setting remains the same.

At the end of the day though it's just a method of working. Whichever way works for you, the end result should be the same.
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Why is it, that when you reply to a thread it is like a chapter from "Gone with the wind" ? :lol:
 
classcams said:
Why is it, that when you reply to a thread it is like a chapter from "Gone with the wind" ? :lol:
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I'm trying to be helpful. What's your motivation?
 
Thanks for the great replies guys. I'm a lot more clear on the subject now.
Dub
(hoppy please ignore the gone with the wind comment - any less and i wouldn't have understood what you meant)
 
Why is it, that when you reply to a thread it is like a chapter from "Gone with the wind"


I think that is rather rude of you. I read all "Hoppy "anwers & they are terrific, detailed & written in a way that i can learn . I actually look for his name in the threads because I know I will be educated a little more. Keep it coming Hoppy , I love it . regards colin.
 
dubcat said:
Thanks for the great replies guys. I'm a lot more clear on the subject now.
Dub
(hoppy please ignore the gone with the wind comment - any less and i wouldn't have understood what you meant)
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coljun said:
Why is it, that when you reply to a thread it is like a chapter from "Gone with the wind"

I think that is rather rude of you. I read all "Hoppy "anwers & they are terrific, detailed & written in a way that i can learn . I actually look for his name in the threads because I know I will be educated a little more. Keep it coming Hoppy , I love it . regards colin.
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Cheers guys :)

I really don't mind Classcams. He adds a bit of colour and you never know he might be right one of these days.
 
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