Flash and Shutter speed

Blasted

Blasted

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I have bit of a basic flash question that I can’t seem to get my head around.

I have a Canon 450d and a 430 EX II speedlight.

I have a scenario that I’m soon going to be faced with. I have been asked to take a few pictures at a reception in the afternoon and then in the bar later in the evening, both indoors and I’m assuming the lighting to be not too good in the afternoon and poor in the evening, hence the need for flash.

Now I think I understand a few of the basic issues. If I want to shoot indoors with low light I need to lengthen the exposure to get more light in. By lengthening the exposure without a tripod I could introduce camera shake. I can combat this by increasing the shutter speed though using a small aperture, in this case I would be using either a 17-55 f2.8 or a 50mm f1.8. I could also increase the ISO, but that introduces noise at high levels. I also have a flash diffuser and am aware of bouncing light of ceilings ect to diffuse light and give direction. I have been under the impression people should be shot at 1/60 as a absolute minimum, ideally 1/125 minimum.

What I don’t understand is that when I drop my camera into AV mode for example, I take a picture, the flash fires but the shutter speed is still acting as though the flash isn’t there and exposing for a darker room. I thought the flash would make the shutter speed faster? I have just plugged it in and its running in ETTL.

If you were to be shooting these scenarios what settings would you use?

I’m not quick enough to use manual in this sort of situation so thought AV would be the best, using something like F5.6 or 8 to get people faces nice and focused front to back.

Opinions greatly received?
 
If I understand correctly, AV mode wont set the shutter higher with flash, it simply adjusts the flash output to gain the correct exposure instead. To get a higher shutter, you need manual mode. Set it 1/125 or whatever which whatever aperture and the flash will determine what power it needs to expose correctly. You wont need to change settings once you have your shutter speed and aperture set as the flash will do all the work.
 
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Shooting indoors in a party/pub/bar type setting I have used manual, set your shutter speed for background exposure and the flash will take care of the subjects. This set on flickr is the first time I used flash in this type of situation, I was lucky as it had a low white ceiling and bounced the flash for most of the shots if not all.
 
foggy4ever said:
set your shutter speed for background exposure and the flash will take care of the subjects.
Click to expand...

But wouldn't that still result in a slow shutter speed and introduce shake?

If its a dark room and you expose for the background you would need to set your flash to second curtain synch to expose for the subject as well wouldn't you?

I need to ensure that my shutter speed remains quick enough to freeze people with out blowing them out.

So should I go into manual and set my shutter speed to say 1/160 then use the iso and aperture to get the right exposure, the flash will take care of its self?
 
I know this may sound untechnical, but for shooting things like parties etc with an on camera flash unit, I found that putting the camera into full auto mode (the green square on Canon) gives quite good results.

You can at least use it to make sure you get some keepers, then play with manual Av/Tv as you want to. I've now found that using wide aperture lenses, and winding up the ISO (to around 800) tends to work for Av, but I'm not sure how your body handles high ISO, but a well exposed image should keep noise to a minimum.

Go and practice in your lounge or whatever to see how you get on.

Steve
 
If the venue has a normalish height white ceiling, this is easy.

The flash is your main light source, pointed straight up at the ceiling and then the diffuser (what is it?) will provide a direct fill-in component that works really well to lift faces and put a sparkle in the eyes. It's also good for getting some light under big wedding hats.

You then want to balance the flash with the ambient background light. Now you can make this as easy or hard as you want (use any mode you like) but given what you've said here the easiest is to use P. It will do the balance automatically but will not allow the shutter speed to drop below 1/60sec with flash. You then adjust the flash/ambient balance by adjusting the flash exposure with +/- compensation on the gun, and the ambient with +/- compensation on the camera. Exposure sorted :thumbs: (Edit: there is also an option in custom functions to stop the shutter speed dropping below 1/60sec in Av mode, if you prefer.)

Things to watch - depending on the ambient light level, adjust ISO to keep the shutter speed in the right zone. For normal social stuff, running down to 1/60sec should be okay. Don't worry about camera shake - use the 17-55 with IS. Push the ISO if you have to (all noise reduction enabled) and it will be fine - under-exposure is the real enemy with noise.

If you have to use low f/numbers like f/2.8, be careful with focus as depth of field will be shallow. With groups of people, try to keep them all the same distance from the camera. Focus on the eyes.

If the ceiling is white, colour should be fine on either AWB or flash setting. The final tweak would be to gel the flash to match the ambient and then do a custom white balance. If the light is normal tungsten, if all else fails use the yellow/orange wrapper from a box of Quality Street - works quite well ;)
 
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Blasted said:
But wouldn't that still result in a slow shutter speed and introduce shake?

If its a dark room and you expose for the background you would need to set your flash to second curtain synch to expose for the subject as well wouldn't you?

I need to ensure that my shutter speed remains quick enough to freeze people with out blowing them out.

So should I go into manual and set my shutter speed to say 1/160 then use the iso and aperture to get the right exposure, the flash will take care of its self?
Click to expand...

It's the flash which freezes the action, not the shutter speed
 
Thanks,

Its a sto-fen diffuser that sits over the flash.

I want to be shooting in RAW so will have a bit of flexability with the white balance, I will have to check if P allows RAW though.

Whilst the lens is capable of f2.8 its been remarked that its better stopped down at f4, so either F4 or 5.6, I think will be a sufficient depth of field.
 
Blasted said:
Thanks,

Its a sto-fen diffuser that sits over the flash.

I want to be shooting in RAW so will have a bit of flexability with the white balance, I will have to check if P allows RAW though.

Whilst the lens is capable of f2.8 its been remarked that its better stopped down at f4, so either F4 or 5.6, I think will be a sufficient depth of field.
Click to expand...

Shooting Raw won't help the flash/ambient colour balance. The gel is to get the two a bit closer, so the background doesn't go orange. You can only adjust the overall colour in post processing, not the balance between flash and ambient.

Stofen is good for this kind of thing. If you want to gel the flash, a cellophane sweet wrapper slides under it nicely.
 
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Be careful using a stofen (or any flash diffuser) without knowing why you are using it. If you don't know why you'll sometimes get better results, sometimes worse results but always be draining your flash batteries more!

And i say that as someone who would use a stofen.
 
Thanks guys,

I think I get what's going off now.

I'm at home and pulled the curtains, still lightish though. Chucked a lens cap on the bed and have sat doing the same shot with different settings.

In P mode with no flash, if I let the camera work out the settings I get 2.5 seconds, iso 800 and f2.8. Now there is no way I would shoot like that freehand.

Now if i drop into manual and set the shutter at 160th I can set any aperture I want, the images all come out the same, so I'm assuming the flash is calculating the light output for me.

Ive also had a play with dropping the flash exposure a notch and seeing what that does.

So is a F4 and 1/160th a good area to be in?
 
Go into the menus on your 450D go to the right hand yellow spanner symbol where you will see "Custom Functions (C. Fn)", press SET and move to number 2 in the numbered row at the bottom. Here you have the choice of setting either Auto or 1/200 sec shutter speed when using your flash in AV mode.

A read of the instruction manual with your camera would perhaps help you understand some of the deeper functions available. This is where you'll find things like mirror pre-release and other not often used functions.
 
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Blasted said:
Foggy4ever,

Nice exposures.
Click to expand...

Thanks

Just got back in from work.

Looks like you have got plenty of good advise. All I can say is every situation is different and it's a case of trial and error, I spent about 5 minutes playing with settings and got pretty much what I wanted as the lighting hardly changed through out the night.

Good luck and hope you post the results.
 
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