newbie question about use of a softbox for a speedlite

I just recently took delivery of a Lastolite Ezybox 24x24 softbox for my 600EX-RT (and am using an STE-3 on my 5DM2 to trigger it).
Does it make sense to use ETTL mode on the flash? I'm assuming no because the sensor on the flash head is obstructed by the two diffusion panels.
I suppose the correct way to do it is to use manual flash power (controlled via the STE-3) and adjust my camera settings by using the readings from my Sekonic light meter.

As far as I know, ETTL doesn't rely on the sensor on the flash. TTL stands for Through-The-Lens, after all.

If you're in control of the lighting, and you have time to make adjustments, then use manual mode for both the camera and the flash power. ETTL will adjust flash power based on the contents of the image, and for most studio-style setups you DON'T want this to happen.

For example: You have a model with pale skin and long, full, black hair. You get everything set up so that it's properly exposed when her hair is in a ponytail behind her head. But, then when she lets her hair down and it sweeps around to the sides and front of her face, the camera and ETTL will think "wow, look at all that dark stuff in the image, better boost flash power a little bit."


I've never needed a light meter; I instead use a gray card/exposure target, the blinkies and the histogram. Many people swear by light meters, but after a bit of experience with my gear and tools, I can get my desired exposure with only one or two test shots.

If you're experienced with your light meter, then by all means use it. Just remember that if your subject is far away from the background, the single main-light flash will affect the subject but not the background, or it'll affect the background to a much lesser extent than the subject. Expose with camera settings for the background, expose the subject with the flash.

Do you plan to use the softbox indoors (studio) or outdoors? Will you use only one light source? If it is outdoors, then one source of light is often sufficient (you use it to bring up shadows and/or add catch lights in the model's eyes), and ETTL is the way to go. If it is indoors, one source of light is usually insufficient - you can get away with a reflector doing the fill-in light job, but still will want at least one more flash for the background. With more than one source of light, ETTL is no longer very useful, and it is more convenient to stick to manual flash controls.

Ettl uses the cameras meter to determine the flash output that is needed. So using a flash in a softbox doesn't effect ettl.

Now if you're flash to subject distance is consistent then it makes no sense to use ettl. Manual is a far better option.

If your flash to subject distance is constantly changing then ettl is a beer bet.

coeng wrote in post #17426958
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I suppose the correct way to do it is to use manual flash power (controlled via the STE-3) and adjust my camera settings by using the readings from my Sekonic light meter.

This. ETTL is a PITA and it's unreliable. There are some situations in which it comes in handy, like events or fast shooting where you can't use the lightmeter and can afford the exposure to be a wee bit off. For studio situations, it's manual flash and lightmeter all the way.

I did some testing with softboxes, in cooperation with one of the POTN moderators, testing four models of Canon bodies and multiple flash units, from both Canon and Metz.

We could not find CONSISTENT behavior of ETTL flash in softbox across the various combinations tried...it varied with Canon body model, Canon flash model, Metz flash model. Some combinations overexposed, some combinations underexposed. We tried with heads pointed forward vs. heads pointed to bounce. While we could get ETTL flash to work properly in straight ahead or bounce positions without softbox, something unpredictable would occur when we mounted small softboxes...and we both used the SAME softboxes for the tests! We tried with different lenses. We tried to figure out what variable might account for what behavior...we quit trying, out of frustration with finding no correlation.

And then I did some testing of four brands of ETTL extension cables (two of them different model Canon brand cables) all of which were new, not used. And where the ETTL flash would work somewhat dependably when directly mounted to the camera hotshoe, when you mounted the flash in any of the extension cable shoes the ETTL would be very unpredictable...often times there would be full power overexposure even though the flash ready indication in the viewfinder showed that the camera recognized an ETTL flash connected. A very common complaint among ETTL flash users. Even with tripod mounting and no motion of the rig at all to account for any bad contact connection, one might find one full power overexposed flash out of 5 ETTL shots.

To be honest, I can't get ETTL to work reliably even without softboxes, even on-camera.

++1

Wilt, I apologise, as I should have been more clear and expounded.

When I speak of unreliability it's not about the capabilities of the flash unit: I'm talking about exposure. Because ETTL relies on TTL metering, the flash output can vary –some times by a lot– if your metered zone moves in the frame. Say, you've a white dog against a black wall and have had the camera meter for the dog: all is well, ETTL is ready, then the dog moves and the camera meters part of the wall, ETTL says 'oh! New meter values, more oomph is needed!', pop... the dog is blown out. Whereas when you're using manual and/or a lightmeter, it doesn't matter what the camera or the flash 'think', the ouput will always be the one you choose: if the dog gets blown out or made black it's the photographer's fault (or intention), not the equipment's.

If both camera and subject are locked, ETTL won't have this problem –of course, if neither are moving, why use ETTL at all anyway?

If I want dependability/reliable exposure with flash, I put my Metz flash in photosensor Auto, and NOT use ETTL!

Wilt wrote in post #17427194
If I want dependability/reliable exposure with flash, I put my Metz flash in photosensor Auto, and NOT use ETTL!

I'll make sure to remember that when I get another Metz to replace the 58 AF-2 that died. I only use ETTL for macro, for everything else it's manual.

I've tried to use ETTL for events a couple of times and it was a complete disaster.

Thing is, I don't think Canon flashes have photosensor auto mode –however, I've never touched a 600EX.

pulsar123 wrote in post #17427103
Do you plan to use the softbox indoors (studio) or outdoors? Will you use only one light source? If it is outdoors, then one source of light is often sufficient (you use it to bring up shadows and/or add catch lights in the model's eyes), and ETTL is the way to go. If it is indoors, one source of light is usually insufficient - you can get away with a reflector doing the fill-in light job, but still will want at least one more flash for the background. With more than one source of light, ETTL is no longer very useful, and it is more convenient to stick to manual flash controls.

Mostly indoors and other than the ambient daylight or ceiling lights it will be my only light source.

gremlin75 wrote in post #17427126
Ettl uses the cameras meter to determine the flash output that is needed. So using a flash in a softbox doesn't effect ettl.

Now if you're flash to subject distance is consistent then it makes no sense to use ettl. Manual is a far better option.

If your flash to subject distance is constantly changing then ettl is a beer bet.

Makes sense, thanks. But what is the light sensor on the flash head for then?

coeng wrote in post #17427305
Makes sense, thanks. But what is the light sensor on the flash head for then?

It's an IR receiver, for Canon transmitters that used an IR signal instead of a radio signal such as the older ST-E2.

Canon FINALLY got with the program and changed from IR to radio. The ST-E3 uses two-way radio instead of IR, so you won't be needing that IR sensor on the flash.

I think the red panel on the front of the flash also houses the IR-based autofocus assist beam, which you won't be using in the scenario you're describing. It's really only for on-camera hotshoe flash use, in lighting that is too dim for standard autofocus.

On the Flash head or Flash body?

If the latter, ?the little round recessed 3mm window, the 580Ex II had it as well. The 'External Metering Sensor'.

For the 600Ex-RT see pages 36 & 37 - nothing to do with TTL nor ETTL - and no use in softboxes. It can work OK with reflective umbrellas.

Alveric wrote in post #17427211
Thing is, I don't think Canon flashes have photosensor auto mode –however, I've never touched a 600EX.

Yes, Canon does have a photosensor in the flash, and you use it in External mode...thing is, Canon's photosensor mode is notoriously known since its introduction on the 580EXII as UNDERexposing by -2EV, and the 600EX continues this tradition of bad flash from Canon engineers !