Flash Confusion!!!!!!!!!!!!!!!!!!!!!!

[flyingdogguitar]

Hi everyone,
Have recently purchased a EOS 10D, and I'm very impressed with the results thus far. I've purchased some basic studio flash heads, soft boxes, reflectors etc. I've been connecting the sync cord into the camera, and then into the master-flash unit(Off-camera). Will the camera calculate the correct exposure, and can some kind person explain to me the difference between E-TTL and TTL metering. Or do I need to have the camera set to manual and experiment with various camera exposures. I've just purchased a flash-meter off of ebay, can anyone explain an easy way of using the meter for correct portrait exposures?

Looking forward in anticpation

David Carey

[robertwgross]

You are probably going to have to shoot with manual exposure. The Canon cameras like this do E-TTL as their primary flash mode.

In a typical film camera, TTL (through the lens) metering works like this. When the shutter is pushed and the mirror flies, light comes through the lens and is reflected off the film surface onto a sensor. The sensor tells the exposure computer how much light it saw, so the shutter or aperture can be started, stopped, opened, or closed to get the exposure correct.

In a typical digital camera, you don't have any film surface, so you can't do it the same way. Instead, an Evaluative-TTL process involves a preliminary flash of low intensity, and a sensor reads the light reflected off the subject. Then a scant fraction of a second later, the real flash is fired with the calculated aperture or shutter settings applied.

---Bob Gross---

[scottbergerphoto]

Since you are using studio flash heads, I assume you are using a PC cord or wireless trigger. The only information exchanged between the camera and the lights in that situation is the camera telling the lights to fire. That's it. You have to adjust the lights and camera with a flash meter like the Sekonic L358. The only way to get ETTL is with a flash unit dedicated to Canon ETTL sitting on the hot shoe, on an Off the Shoe Cord 2, or controlled by an STE2 sitting in the hot shoe.
There is no TTL in Canon digital cameras. In TTL the flash metering takes place with the shutter open by readings of reflected light off of the film plane. In ETTL, a pre flash fires before the shutter opens, and the camera sets the flash output based on the light reflected back from the preflash. Once the main flash fires with the shutter open, there is no feedback.
For more information go to: www.photonotes.org/articles/eos-flash
regards,
Scott

[DaveG]

Hi everyone,
Have recently purchased a EOS 10D, and I'm very impressed with the results thus far. I've purchased some basic studio flash heads, soft boxes, reflectors etc. I've been connecting the sync cord into the camera, and then into the master-flash unit(Off-camera). Will the camera calculate the correct exposure, and can some kind person explain to me the difference between E-TTL and TTL metering. Or do I need to have the camera set to manual and experiment with various camera exposures. I've just purchased a flash-meter off of ebay, can anyone explain an easy way of using the meter for correct portrait exposures?

Looking forward in anticpation

David Carey

The first thing is to understand that studio strobe lights are completely manual
and as stupid as a brick. But they are highly controllable and very consistent,
flash pop after flash pop. But you have to measure them and measure them in a
very specific way.

E-TTL is Canon’s special automatic flash system. It doesn’t work at all but we
kid ourselves that it does. Even Canon recognizes - at least quietly - that it sucks;
resulting in the “can’t be any worse” E-TTL II system in the MarkII.

Anyway I digress and this is that about studio flashes:

With multiple flashes you can set up lighting ratios that will let you light the
subject in a professional looking way. I should say that I'm using light and flash
interchangeably. I'm also assuming that you are using umbrellas or softboxes on
the flash heads as well.

I hope that your flash meter is accurate, since it is an important tool to building a
lighting ratio. You'll need two lights in order to create a ratio, and don't be
intimidated by that term. What you are trying to do is to create light that does a
few things. First it has a direction and that will be your main light.

Set up your main (sometimes called a key) light about 45 degrees to one side of
your portrait subject. It can actually go anywhere, but this is the best placement
for basic portrait lighting. Take a meter reading of this light alone, and lets say
it's f8.

Now set up another light within 20 degrees of your camera position. This will be
the fill light. Either through the controls on this flash or by simply moving it
closer or farther away from the subject, adjust it so it’s quite one stop less than
the main. Measure this light alone as well, so that the main doesn't bias your
meter reading. Again as an example lets say f5.6 and a bit.

You have just created a 3:1 lighting ratio. I'm not going to explain ratios any
more than that, since we all think in stops anyway. But you have direction from
the main (and you should have your subject's body turned towards the main).
You also have shadow but you'll have detail in this shadow and that what the fill
has provided. There's no film or digital capture that won't handle a one stop
difference between the highlight and the shadow.

But you DO have to meter both of these flashes together to get you taking
exposure. If the main is f8, the fill f5.6 and a bit the combination will be f8 & a
half or thereabouts, so you shoot at that. If you were shooting colour neg film
you could shoot at f5.6, f8 or f 8 &1/2 and it would hardly matter, but with slide
film or digital capture the films/capture don’t have the latitude, and you will
overexpose and blow out the highlights if you don’t shoot at the combined flash
output.

Everything else in lighting is spice in the soup. You can add background lights
or hair lights or whatever. But lighting starts as a main and a fill. Always.

[chris.bailey]

Cant add much to what Dave said as its a nice outline.

A word of warning is that the Sync voltage may exceed that recommended by Canon (6v). There are reports of using studio lights plugged in diect causing the flash sync contacts to burn out. My bowens units have a sync voltage of 24v. Safe therefore to put something like a Wein Safe Sync between the camera and the sync cable.

Another point is that you can use up to 1/250 (for mine anyway) which enables you to open up the shutter a bit and get a bit of depth of field going.

Flash meters are hard to get used to and you need one setup for flash readings (white flat disc rather than a dome) so you can take readings on each lamp. I always read off the main light with the fill off, vice versa and then both with the flash meter pointing towards the camera. Expect to then play around by 1/2 a stop to get the desire effect spot on. After a shile you get a feel for it. I will then take some reading off the background. If the reading off the background is much less than 2 stops below then it will apear black, whatever colour it actually is, 2 stops above and it will be white (ish).

[DaveG]

Cant add much to what Dave said as its a nice outline.

Another point is that you can use up to 1/250 (for mine anyway) which enables you to open up the shutter a bit and get a bit of depth of field going.

Flash meters are hard to get used to and you need one setup for flash readings (white flat disc rather than a dome) so you can take readings on each lamp.

The synch speed of the 10D is 1/200 of a second so 1/250 will be off synch, at least on that camera.

You seem to suggest that fast synch shutterspeeds like 1/250 would be useful for what I'm infering to be fill flash. Outside on a bright day then you're completely right. But if I'm inside trying to do ambient light fill flash, then the shutterspeeds would be much slower.

More to the point I wouldn't use ambient light at all when I was using studio lighting. If the room is dark then the only ambient light is from the modeling lights and they will cause a colour cast. If there's enough natural ambient light in the room then that could mess up the lighting ratio since you've introduced more fill light. That light also comes from above and I may or may not want it striking the subject from that direction.

Mostly though in a controlled studio lighting situation I will use the controls on the strobes as well as their placement to control the depth of field without any attempt to use the ambient light. It's directional, it's precise and there's no colour cast.

I use the regular dome on my Minolta IVf flash meter. As long as I'm metering each flash individually the flat disk won't be any better than the dome. Now the flat disk won't hurt and is better when I HAVE to meter the strobes individually, but with them all on. I still try to use my hand as a flag to block the light from the meter no matter what disk/dome I'm using.