which in-camera metering for flash

Janice

Janice

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Janice
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If you are shooting a subject in a studio with a white background which is lit by flash... what in-camera metering mode should you use?
I would measure the flash by a handheld meter, but would I use the spot metering of the camera to expose for the skin on the face?


If I use matrix it will take into account all the bright white background too and underexpose the shot wont it?
 
Not sure the in camera metering really works in the studio unless using continuous lighting but I might be wrong. Because the flash isn't on when the camera meters it would give you a duff reading and studio flash doesn't use a pre-flash to help with metering like your on camera flash does.

I do stand to be corrected though as this is only theory.
 
What kind of flash is being used?

If it's say, ETTL, then the camera meters when the flash pre-fires in which case spot or partial to take a reading from the skin using FEL might be best.

If you're using studio flash kit of some sort then spot or partial again with lots of checking the histogram and ajusting the output assuming you don't have a flash meter.
 
What pxl8 said. The camera fires a pre flash for the purpose of metering. It's so brief and rapid you'll struggle to see it - but it does.

I'd use spot metering (or FEL) to meter for the face and adjust the output of the bg flash accordingly.
 
If you are using studio flash then use a flash meter to determine the exposure and set your camera to manual and set accordingly, usually 1/60th at f?
 
Gary Bagshawe said:
and set your camera to manual and set accordingly, usually 1/60th at f?
Click to expand...

I appreciate what you are saying........but surely it must matter which mode the camera is in.....doesnt it?
 
Janice, are you using the camera or a separate flash meter to calculate the correct exposure?
 
pxl8 said:
Janice, are you using the camera or a separate flash meter to calculate the correct exposure?
Click to expand...

Well, I will be using a flash meter to get the exposure of the white background that will be lit by a studio flash behind the subject.........but as my conservatory is so light I dont actually need any more lights at the front so I thought I would meter from the camera for the subject?


If I put a sigma flash on the camera to brighten up the face....then what metering system would I use in the camera?

Im really sorry guys,,, I know I keep asking these inane questions... but the whole thing is doing my head in.
If i had a black room Id probably be ok. Id work out which lights go where and what power.... meter with the handheld and just snap away.

however I just have so many options in my head as to what to put where, that I cant get it sorted.
I can actually take shots out there with no lighting at all except natural...so you can see my dilema. :shrug:
 
Ok, I understand what you're trying to do now. I'm not sure how well it's going to work mixing TTL flash with manual but you could try the following.

Shoot in manual mode using the flash meter settings and let the Sigma worry about its exposure, tweak the FEC as necessary.

But I suspect there might be problems because the flashes aren't in sync so the Sigma might see the background flash or it might not. It would be a lot simpler to use a 2nd studio head for a bit of fill on the face and adjust its power accordingly.
 
I could use the sigma off camera wirelessly on manual.

I STILL cant take in that as the camera takes a picture... the metering mode it is in doesnt make any difference. spot, evaluative or whatever.

I think i will have to do a test to prove it to myself! Its the only way I can get it into my thick head!:shrug: :bang:
 
It's a little complicated but the flash metering kind of does it's own thing which makes it tricky to use in situations like this. Another problem you might have is if the flash head is firing as a slave rather than by cord. The pre-flash from the Sigma will trigger it too early.

Using the Sigma off camera in manual mode and adjusting the power is a good way to go tho :thumbs:
 
Thanks for your patience Pxl8!
I cant rest until I fully understand things... I cant just do them blindly!!:thumbs:
 
Janice I think you'd be better off doing it the other way around. Meter from the skin using your flash meter first if you're not using any lights. No point trying to use the camera to do it if you already have the meter out if you ask me. Then use the meter to set the flash level for the BG.

Can't really see the point in shooting in A mode if you've got the meter already, use the meter and shoot in M.
 
pxl8 said:
It's a little complicated but the flash metering kind of does it's own thing which makes it tricky to use in situations like this. Another problem you might have is if the flash head is firing as a slave rather than by cord. The pre-flash from the Sigma will trigger it too early.

Using the Sigma off camera in manual mode and adjusting the power is a good way to go tho :thumbs:
Click to expand...


When you say off camera..... do you mean as a slave..... or manual but joined by a lead? i have been using it as a slave but it needs the onboard flash to trigger it which is a pain, so I have to turn that down and diffuse it.
 
Oh dear, it's all getting a bit confusing ;)

Let's start with the basics - what flash gear have you got?
 
Im sorry! i cant believe that everyone else can get pictures with nice white backgrounds and well exposed subjects... and I cant. I'm not thick really! :|

I have a Canon 30d... sigma 500 dg super... and a studio light 180w with a power knob that goes from 1 down to 1/4 with a light stand and white brolly.

The sigma can work wirelessly from the camera but only when it is triggered by the onboard flash. If it is wireless that is slave mode, right?
If it is in just ordinary manual mode it can be put on an off-camera lead with a hotshoe on either end and that way I wont need the onboard to set it off.

If I meter the background while using the studio flash which is facing it... then I meter the subject with the front light on and the background light off, and set the camera for the subject.... wont some of the front light shine past the subject onto the background which you didnt meter for as the front one wasnt on when you metered the background?
 
Slave mode and wireless can be two different things. Wirelessly, it uses a series of pulese from the onboard flash which act as a signal telling it how powerful to flash. They can also be used as a slave where they require only one flash, much in the same way as your studio light (assuming that it's flash and not continuous) which sets them off but you have to set the power manually yourself.
 
Janice said:
If I meter the background while using the studio flash which is facing it... then I meter the subject with the front light on and the background light off, and set the camera for the subject.... wont some of the front light shine past the subject onto the background which you didnt meter for as the front one wasnt on when you metered the background?
Click to expand...

You might get some light spillage depending on how the light is set up, zoom, softbox fitted maybe and distance. But you're blowing the background out anyway aren't you so a little extra light should make that much difference I wouldn't have thought. If you find it does just turn the background one down a touch.
 
It all sounds so easy... and I understand the theory perfectly.
When I put it into practice I get completely blown out white shots (subject too) underexposed grey shots.... I stood in that conservatory tonight and took about 80 shots.... about 1 looked ok.
 
Ok. Here's how I'd start with that setup.

Sigma says the 500DG will slave from other flash equipment in manual mode so I would hook the 180w head up to the camera via a lead and let the sigma fire as a manual slave. This gets rid of the ETTL metering and sync problems.

Use the Sigma to light your subject - bounced, diffused, whatever. Put in manual mode and take a reading from the face - that will give you the f-stop you need for the subject exposure. Increase or decrease the power on the sigma to get the f-stop you need.

Once you're happy with that take a reading from the background and adjust the power so it's 1.5 to 2 stops brighter than the subject. Then you're good to go.

If the sigma is bounced/diffused then you don't need to worry about spill onto the background as the shadows will be nice and soft and the 180w will be burning it out anyway.

If the 180w works as a slave you could swap the set up and run the 180w as a slave from the Sigma - hook the sigma up to the camera via a lead instead of the 180w. But the important thing is to make sure the sigma is in manual mode not Auto as you want to have full control of the output from both flash units.

Hope that all makes sense.
 
If you're using a semi-auto mode like Aperture or Shutter it could be fooling your metering. Try setting one light up at a time, say the subject light, meter for it with the light meter and set your camera with those figures in manual mode. Then add the BG light, as long as that doesn't fall on the subject your subject should still be perfectly exposed and the background will do whatever until you get the power how you want it.

I would try using your sigma as a slave instead of wirelessly because it could be the in camera metering adjusting the sigma's power each shot too. Think of it as another studio light. You would want the same power each time not a different one depending on how the camera is metering that time.
 
pxl8 said:
Sigma says the 500DG will slave from other flash equipment in manual mode so I would hook the 180w head up to the camera via a lead and let the sigma fire as a manual slave. This gets rid of the ETTL metering and sync problems.
Click to expand...
so the sigma would fire by the the 180w firing? I have been using it in manual slave mode all along..... but triggered by the onboard flash.

pxl8 said:
If the 180w works as a slave you could swap the set up and run the 180w as a slave from the Sigma - hook the sigma up to the camera via a lead instead of the 180w.
Click to expand...
sigma doesnt have a sync socket......so it would have to be an adapter from hot shoe to sync.

180w is triggered by another flash....so yes, either setup should work.

I am very grateful to you PXL8 for taking the time to explain. Once i get my sekonic flash meter I should find it easier. Like i said... I can see it in theory, but it doesnt bear out in the practical.
Waht about if there is a lot of ambient light.....all round including from the roof (although diffused). The same practice will work?
 
Ok, it's all sounding good. I think the problems you've had so far have been down to the sync problem from the on board flash triggering the others too early when the pre-flash fires. As a test you could try the Sigma on camera in manual mode and the 180w in slave mode. Then play with the manual power settings until it looks good on the LCD/histogram - should be more consistent that way.

Shooting with lots of daylight could be a problem. I would suggest taking a reading from the subject with the camera and then try and get the flash settings a good 3 stops higher if you can to minimize the effect the daylight will have.
 
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