Using Flash!

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Hi
Ive had very mixed results with flash, over exposure, under exposure...it seems I'm not compatable with it???
Can anyone offer some advice on using flash effectively? Good books? etc!!

I want to branch into portrait stuff but not until I can get consistant results.

TIA
Andy
 
what settings are you using the flash on Andy?
 
hmmm me too..ive barely scratched the surface of the flash, maybe Steve can come up with something, he uused to own the very same unit
 
Cheers
Can I just add that Matt's Avatar is a self portrait! ;)
I Like the head Idea, but I have kids, and they are free!! :) I could do with a book which takes me through the various stages. I dont fully understand flash photography so need it explaining, otherwise practicing without understanding would be like a virgin having sex with my wife, no real Idea and absolutly no feedback!!! ;)
 
thanks Andy...
 
I thought this thread was going to turn into another educational one.... looks like its the blind leading the blind on flash use :)

I'm still on the learning curve too. When I use the 580EX flash (as the only light source) I put the camera on manual and set it so it cannot take a picture in available light - usually 100 iso 1/250th and f8. Then I just let the flash decide how much light to push out for the right exposure. It seems to get it right most of the time. Only flaw with that plan is the flash really pumps out some power if you shoot a bigger area, so to stop getting moaned at for blinding people I up the iso a bit and maybe open the aperture a touch.

For some reason the 20D seem to under expose with flash so I usually have flash compensation set to + 2/3.

Getting fill flash right seems to be more of an art and one I have yet to tackle.

Been playing with the strobe mode.... manual settings...pure guesswork....check histogram/adjust/try again. Bit unpleasant to work with though :confused:

/waits for flash expert.....
 
I've always thought that the best way to sucessful AND consistant flash is to take complete control away from the software and run the show yourself.

People tend to think that using flash is complicated and that we need the camera and the head to work out all the questions and the answers for us. It's really pretty simple when you take a step back and look at it again.

The only difference between flash and existing light work is that we can't measure the light from the flash and then set the camera. Well you can if you have time to wave a meter around but most people dont. We can control the output though so setting up our exposure is not all that different.

Give it a go. Set the camera (on a tripod if you have one) with the flash on so you have a fixed distance to an object. Have the shutter set to the flash sync speed and the flash to full power.

Now adjust the aperture untill you have an exposure you're happy with. You've now got a base to work from....;

a full power flash burst to a subject at x distance, with x ISO needs an f stop of x.

If your subject is nearer, you need less light, further away and you need more. Without going to far into the theory, light works on the inverse square law, which means if the subject distance doubles you need four times as much light to maintain the same level of illumination. All that means in english is that you need to expriment with distance a little and you'll very soon be quite instinctive. If the subject moves from 5ft to 10ft away, you need to open the aperture by two stops.

Once you've got a base figure to work from, you have three ways to control the flash. The flash output power, the ISO and the aperture. Since all you need to do is raise or lower the one of these depending on distance, you can chose the one that most fits with your needs at the time. For instance if you need DoF control, then flash power or ISO are the better options etc etc.

This is really all very easy to get to grips with and once you start to use it becomes natural very quickly.

The other thing that comes into the equation when you are using fill in flash is the shutter speed. When you are using 100% flash illumination the flash duration is far faster than your fastest shutter speed but when you have ambient light too, the shutter allows you to control this without any effect on the flash.

Anyway, enough waffle from me. :whistle2:
 
Gonna re read that when i have less alcohol in my system, but it seems to make some sense. I'm sure some stupid questions will arrise in a sober state!

love the sig BTW quite apt ;)
 
Gonna re read that when i have less alcohol in my system
Click to expand...

Me too. I doubt it's gonna make any sense tomorrow. :D
 
Guys, this is a huge subject, but you shouldn't really be having major problems with a modern DSLR and a dedicated flashgun. The first thing to understand is that there is a maximum shutter speed you can use, which in the case of the 350D is 1/200th second , and with the 20D, 1/250th second. YOU CAN ALSO USER ANY SLOWER SHUTTER SPEED.

Set the flash mode on TTL (ETTL in the case of Canon). There are two basic ways to use the flash...

1. As the main or sole source of illumination...

A dark or dimly lit room for example. In this scenario the flash will fire probably at 1/60 sec or faster- the light hits the subject, bounces back into the lens and the camera processor quenches the flash when it deems exposure is correct. This produces the typical night out shots we see where the group in the foreground are illuminated by flash, but the room behind them is dark. This is the drawback of flash - it can only correctly illuminate within a very narrow plane from the camera. Obviously if the flash continued outputting sufficient light to light the background then the group in the foreground would be over-flashed.

2. As Fill Flash...

With this method, the flash is balanced with the prevailing light, be it, available light indoors, or outside in bright sunshine. If we now take our group again, this time we'll take a meter reading for the natural room light. Lets's say it's 1/25th with the lens wide open. If we use Shutter Priority (TV) and set a shutter speed of 1/25th, then the flash will balance it's output to the room lighting. The foreground figures will be nicley lit, but you'll see more of the room behind captured by the prevailing ambient light.

Again, outside in daylight, lets say you get an ambient reading of 1/125th at f8. Setting a shutter speed of 1/125th in TV (SP) mode will produce a properly exposed natural light shot with the main subject just lit sufficiently by the flash to brighten it up.

Generally speaking, keep your apertures on the largish side. Using small apertures just forces the flash to output more light, uses more power, and regardless of how powerful it is it will soon reach it's limits with small apertures.

Hope that helps a little chaps. It would be a lot easier to explain it all round the table at the pub. :beer:
 
:laugh1:

It makes your 'ead hurt don't it!
 
Yep!
Down the pub at this point seems a very reasonable suggestion.
 
just as a matter of interest I've always set flash exposure compensation on the flash unit.

There's a flash exposure control facility on the 20D, does it/can it control an external unit as well?

I would RTFM but I can't find it :embarasse
 
dod said:
just as a matter of interest I've always set flash exposure compensation on the flash unit.

There's a flash exposure control facility on the 20D, does it/can it control an external unit as well?
Click to expand...

If you set exposure compensation in the camera, then it will have an effect on the ambient light exposure, and possibly the flash too, in fact it's highly likely (given the communication between camera and flash these days) that it would just reduce the camera exposure and the flash exposure by equal amounts so you don't wanna be doing that, particularly for fill flash where the whole idea is to balance the flash with the available light. Setting the exposure compensation on the flash gun allows you to adjust the output of the flash as necessary to balance it with the prevailing natural light. In short - keep setting it on the flashgun. :)
I would RTFM but I can't find it :embarasse
Click to expand...

LOL. You'd probably be none the wiser when you'd struggled with the dodgy Japanese/English interpretations you still get in some of these manuals. :confused:
 
Actually as long as the flash is set on TTL (Thru The Lens) exposure, and you're using either the fastest shutter sync speed or a slower one, then it matters not whether you're in AP, SP or Manual Mode on the camera - the level of integration with guns like the 430EX and 580EX should give you either an ideal exposure, or put you pretty close to it, so that only small amounts of compensation are required.

Providing you're shooting at moderate distances and not using too small an aperture you shouldn't have any problems.

I went to see Stevie Wonder at the NEC one time and people were whacking away with flash on tiny little compacts right from the back of the hall with no chance of the flash reaching further than three or four rows in front of them!

With a gun such as the 580EX used on full power and the camera at full aperture, you'd probably just be able to pick Stevie out on stage. :snap1:
 
Your head still a little fuzzy CT? ;)
dod said:
There's a flash exposure control facility on the 20D
Click to expand...

The flash compensation should only effect the flash output and not the camera settings at all. It will certainly work with a canon unit and the better dedicated makes like metz, quantum, sigma and the like. :)
 
dazzajl said:
Your head still a little fuzzy CT? ;)
Click to expand...

LOL. I misread Doddy's post actually, I thought he was talking about 'normal' camera exposure compensation. :nut:
 
you had me even more confused CT :dizzy:
 
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