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Fill in flash with digital


DAVID LYDIATE 18 305
27 Jun 2006 5:38PM
I am currently reading "The Magic Lantern Guide" for the canon 350D

I understand that to apply fill in flash you under expose the flash from the exposure given by the camera.

How would fill in flash be applied to a scene if I was using 350D & 580 ex?

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croberts 16 2.2k 8 Ireland
27 Jun 2006 5:48PM
not sure about 350D, but with any of the canon models i use, theres an "auto reduction of fill flash" custom function, thats set to "enable" by default.

I have it turned off, as the flash works perfectly for fill, in AV mode especially, without any compensation, or reduction.

I find the 580ex almost always 1 stop under, in most situations, so its perfect for fill in, and i keep it +2/3rds the rest of the time.
JohnHawthorne 14 1.7k 5 Scotland
27 Jun 2006 6:01PM
I must admit this is something I don't know how to do (cos I haven't bothered to read the manual yet) except to stick it in manual and think about it.

With the camera in manual, meter for the highlights (usually the backlighting). With the flashgun in manual, choose a setting that will just about light the foreground. Check image and histogram and try a different flash power if it didn't work.

Unfortunately this way seems to work quite easily for me so there's little incentive for me to RTFM.
DAVID LYDIATE 18 305
27 Jun 2006 6:18PM
Thanks for that replies

I am now on pg 132 of The above mentioned guide and if anyone has the guide it would be good to hear from you, as well as anyone else of course who can help me understand.

Refering to the explanation for using AV mode it states "Using this mode lets you balance the flash with existing light and it allows you to control Depth of Field in the composition. By selecting the aperture, you are also able to influence the range of flash. The Aperture can be selected by turning the main dial and watching the flash's LCD panel until the desired range appears. The camera calculates the lighting conditions and automatically sets the correct flash shutter speed for the ambient light."

The para refers firstly to balancing flash with existing light, which indicates fill-in with the use of the word "balancing". It then goes onto say "The camera calculates the lighting conditionsand automatically sets the correct flash shutter speed for the ambient light"

From the quotes highlighted, should I assume that this is a form of auto fill-in without you having to phisically alter specific settings?

I will be using the Canon 580ex speedlite with this mode
croberts 16 2.2k 8 Ireland
27 Jun 2006 6:33PM

Quote:From the quotes highlighted, should I assume that this is a form of auto fill-in without you having to phisically alter specific settings?


yes, you'll find it works very well in AV mode. With almost no intervention. and as your book says, you'll see a flash coverage reading on the back of the flash, increasing and decreasing, as you adjust the aperture.

if your lens has a distance scale, you can tell straight away if the flash has enough power to light your subjects.

Dont forget, though, as with any reflective metering,
you'll need to turn the flash up if theres lots of very pale tones, and vice versa.


but, hey, why not go outside and play with it, and see. Then take a mental note of what works.
nikon5700ite 16 1.8k
27 Jun 2006 7:10PM
It may help you understand what the camera is doing if you remember to old rule that the aperture controls the flash and the shutter the ambient light Naturally there has to be the normal relationship between both for correct exposure by the ambient light.

There might be a small glitch that in bright light, if you first selected a large aperture[for less DoF], the camera might select a matching shutter speed higher than the camera sync's at and only part of the shot will be illuminated by the flash*. I would hope that a camera as clever as it appears to be would have a warning signal when that was likely.

The 'balancing' I assume to be the relative balance between ambient and flash light as suggested above. Some people are happy for the flash to be very obvious and being the 'main light source' whereas others prefer a softer result where the flash simply lightens the darker shadows, perhaps a 2 stop reduction of the flash power.

*You need to appreciate that with a focal plane shutter at higher speeds the second 'coverup blind' starts to cross the sensor/film before the first 'open-up blind' has reached the far side of the sensor. So during the very short duration of the flash only part of the sensor is exposed. This 'sync shutter speed' can be as low as 1/200 and the only way to use a faster shutter is when you have a flash unit which pulses to cover a 1/500 shutter.
Sorry if you already know all this Smile
DAVID LYDIATE 18 305
27 Jun 2006 10:03PM
Thanks once again for the replies.
DAVID LYDIATE 18 305
28 Jun 2006 2:19PM
Page 138 of the book discusses Wireless ETTL Flash,
As I said I will use the 580ex

On the subject of Wireless ETTL Flash it states "With The Wireless E-TTL Feature you can use up two 3 groups of speedlites 580exs, 550exs or 440exs for more natural lighting or emphasis.(The number of Flash groups is limited to 3, the number of actual flash units is unlimited). The master unit and the camera controle the exposure. A switch on the back of the foot of the 580EX and 550EX allows you to seslect whether the flash will be used as a slave unit."

In conclusion this sounds like a studio set up, whereby studio conventional flash units have been replaced by several flash units, or a combination of studio flash units are combined with on camera flash units.
eg hair light=f8
main light =f8
580 ex (fill light)=f4

The 580ex or many of them are placed like studio lights around the subject, a signal from the camera sets everything off when fired or perhaps one flash is left on the camera to send a signal to the rest?
Pete Plus
19 18.8k 97 England
28 Jun 2006 9:29PM
That's right, although the hair light may be better giving one stop more exposure than the main light ie f/11.

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