Portable studio and an ETTL question

[OviV]

I setup a portable studio for Baseball Team and Individual pictures out at the park. It consists of a 10x10 white canopy with 3 walls and a backdrop. In the past I have used the on camera flash for fill and to get a spark on the eyes. This trows a shadow on the backdrop which I later clone out in PP. This year I decided to setup 2 of my alienbees clamped above and in front of the backdrop to get rid of the shadow. I thought the pre-flash fron the on-camera flash would fire my AB so I was sure I was going to have to shoot in Manual to avoid that. I did some testing and I was shocked to find out that I can shoot in TV mode.

Does the ETTL not fire a pre-flash in TV mode?
Are my lights recycling fast enough to fire again (I doubt it since I am using a Vagabond 150)?
Do the ABs ignore the pre-flash?

Here is a picture without the ABs. You can clearly see the shadow:
http://www.shareapicture.com/vsalbum/getpic.aspx?fld=/OviV/Photography&pic=noab.jpg&OV=0

Here is one with the ABs shot in Tv Mode. No shadow so obviously the lights are doing their thing:
http://www.shareapicture.com/vsalbum/getpic.aspx?fld=/OviV/Photography&pic=ab.jpg&OV=0

[PacAce]

No the ABs do not ignore the free flash. If you're not using the full charge of the strobe, it may be able to fire off two consecutive flashes in a row without a problem. But I've found that it's not always consistent. And it also depends on how far away you stand from the AB you stand with your flash. If you are right beside it, you'll have more successes than if you're several feet away from it and the slave trigger of the AB needs to rely on the flash bouncing off walls to fire.

[FlashZebra]

Why is Av mode important?

You seem to have a static setup that all you need to do is iron out the needed exposures from your various light placements, and just do the same thing over and over.

I would not risk any preflash problem. Just get all you manual flash setting set, and if you need to use an on camera flash to fire your background lights via a optical slave, use the on camera flash in manual mode.

Half E-TTL flash control + half manual flash control = big problems.

I would not want to be in Av mode, with the shutter varying, with a couple of studio strobes ready to cause you big problems if the shutter speed creeps over your maximum shutter speed.

Get something fully manual and stable and just serve that up over and over.

Enjoy! Lon

[OviV]

I am not using Av, I am using Tv. I use Tv because I want to make sure I do not exceed the sync speed. I can not rely on one manual setting because I am still outdoors and my light (in S. Florida's summer) is constantly changing. I was fully prepared to go with manual and adjust my settings as needed but it seems as though I don't have to which is a welcomed surpise since my shooting has to go very fast or I get seriously backed up with kids that need to get to a game. The purpose of my post is to see if someone has any ideas as to why this is working when I feel as though it should not. To me the most likely reason is that the lights are firing twice since I am using them at about 1/4 power.

Ovi

[FlashZebra]

I am not using Av, I am using Tv. I use Tv because I want to make sure I do not exceed the sync speed. I can not rely on one manual setting because I am still outdoors and my light (in S. Florida's summer) is constantly changing. I was fully prepared to go with manual and adjust my settings as needed but it seems as though I don't have to which is a welcomed surpise since my shooting has to go very fast or I get seriously backed up with kids that need to get to a game. The purpose of my post is to see if someone has any ideas as to why this is working when I feel as though it should not. To me the most likely reason is that the lights are firing twice since I am using them at about 1/4 power.

Ovi
Very sorry about my very big mistake (see Tv think Av).

Enjoy! Lon

[MrScott]

So, either include exif and flash power OR take these exact same shots at night with the same setup. I'm guessing 97% of your light is from the white tent.

BTW how hot is it in there with 3 sides and a BG?

[OviV]

Exif on the fisrt picture is 1/125 at f3.5 on the second it is 1/50 at f6.3 (lowered my shutter speed by mistake since I keep it at 1/125). Most definitely the majority of my light comes from the white tent. This is my intent. As I stated in my original post, the on-camera flash is for fill and for the sparkle in the eyes. The Alien Bees are there only to kill the shadow from the on-camera flash. I turn the flash compensation down by 1/2 so flash power is minimal. I set the power on the 2 AB400s to 1/4 to 1/2 power. I am not concerned with the lighting, I have been doing this for a long time although the ABs for the backdrop is something new I am trying. My only "concern" was why the Alien Beens are working as optical slaves in Tv mode.

Ovi

[FlashZebra]

It seems that you also suspect a preflash is occurring and you are just getting lucky.

If you suspect the Alien Bee units are actually firing more than one time due to the low power setting you are using, I would force the issue and turn them all the way up and see what happens. In this case it is unlikely they will be able to respond to the final flash quick enough, and you will know the preflash is an issue. Working off a second flash burst is likely to be eratic.

If the preflash on the Alien Bee units are the only problem, you may want to investigate special optical slaves that ignore the preflash.

I have provided a link to some units by Wein that can do this. You could use one of these special optical slaves plugged into each of the Alien Bee units. I think plugging something into the sync port of the Alien Bee unit turns off the built in optical slave, but if in doubt you could blind the slave on the Alien Bee units with an ad hoc opaque cover.

Also radio control of the Alien Bee units would negate the preflash issue.

See (near the bottom of the page, the units under "SSLED":
http://www.weinproducts.com/safesyncs.htm

Is the subject in the shade of your tent?

If so, are you sure that if you fix a manual exposure at something like ISO 100, F/11, 1/250 that the varying sun will affect the exposure enough? This would mostly depend on the density of that tent fabric. And in any case you are going to be close, even at ISO 100, F/11, 1/250 (almost the exact same exposure the "sunny 16" rule).

But, if that tent knocks the exposure down at least three stops (only you can determine if it does), you might just be able to pull off a static manual exposure, regardless of the sun. If the tent knocks three stops off the outside sun, that would mean that "worst case" the sun would only be contributing 1/8 of a stop to the exposure. This might not be enough to be important. If the tent knocks four stops off the sun, you definately can ignore the contribution of the sun as it would only be 1/16 (about 6%) of the overall exposure.

Enjoy! Lon

[SkipD]

The best way to reduce the background shadow would be to get the flash directly above the lens and as far above the lens as would be practical using a Off-Camera Shoe Cord 2 instead of having the flash mounted to the camera (obvious because of the shadow location). I would even try to have the flash bouncing off a smallish (such as 42") umbrella above the camera. You could use FEC (Flash Exposure Compensation) to vary the intensity of the light from the flash.

I would also recommend shooting in P Mode experimentally. That mode seems to do quite nicely for most of the on-camera flash (as opposed to studio flash) work that I do. My 420EX does not allow for manual flash output control.

[OviV]

As the day progresses (I start shooting at 8 am and finish at 4 pm), my light can vary by way more than 3 stops. Even within minutes the light can change drastically by going from overcast to bright clear skies. I keep the flash on camera for the sake of convenience. Keep in mind that I am shooting in a dusty, humid, and hot park and I am shooting restless children. I can not complicate my life much more. I shoot 40 teams on average with 13 kids per team. I don't have a problem with shooting Manual, but if I don't have to, it is a good thing. Maybe I am getting lucky with the lights recycling fast enough and maybe when I have a big shoot I'll run out of power on the lights (Only shot about 100 kids last Saturday due to rain) but for now this looks promissing.

Ovi

[FlashZebra]

As the day progresses (I start shooting at 8 am and finish at 4 pm), my light can vary by way more than 3 stops. Even within minutes the light can change drastically by going from overcast to bright clear skies. I keep the flash on camera for the sake of convenience. Keep in mind that I am shooting in a dusty, humid, and hot park and I am shooting restless children. I can not complicate my life much more. I shoot 40 teams on average with 13 kids per team. I don't have a problem with shooting Manual, but if I don't have to, it is a good thing. Maybe I am getting lucky with the lights recycling fast enough and maybe when I have a big shoot I'll run out of power on the lights (Only shot about 100 kids last Saturday due to rain) but for now this looks promissing.

Ovi
It does not matter how much the light varies during the day, if your exposure in the tent is sufficient to overwhelm the brightest condition. Or, in my example enough exposure in the tent to compete well even in the brightest conditions. If you can compete in the brightest condition, anything less than that will be gravy.

When you put up the tent, on a very bright day, meter outside, then meter inside under the same outside conditions. If these exposure readings reveal at least a three stop difference, then it is very likely that you can go with one fixed manual setting regardless of the ambient (from total darkness to brightest day). This is also contingent on you being able to get this exposure inside, ISO 100, F/11, 1/250 sec.

The three stops I cited was not a variance for the outside light ambient for any condition, of couse you can expect daylight to vary a lot more than three stops. But it was a variance inside the tent, compared to the value outside the tent (in the brightest conditions). If the variance is more than 3 stops, it will be even better.

If you have a "thick" tent, you may very well be able to get more than a three stop differental. If it is a "thin" tent, possibly a three stop differental is not possible. Only you can determine this as you have the tent.

In other words, without numbers. It the brightness inside the tent from the light you personally muster from your flash units (not the sun) makes any exposure contribution from light condition outside the tent incidental, there is no reason to even consider the incidental light from the outside (regardless how much it varies outside).

If you can get this three stop variance (and the ISO, F/11, 1/250 second exposure in the tent), you can most likely go all manual and never change any setting regardless of the outside ambient, what could be simpler that this? One constant setup.

Enjoy! Lon

[JMHPhotography]

I am not using Av, I am using Tv. I use Tv because I want to make sure I do not exceed the sync speed. I can not rely on one manual setting because I am still outdoors and my light (in S. Florida's summer) is constantly changing. I was fully prepared to go with manual and adjust my settings as needed but it seems as though I don't have to which is a welcomed surpise since my shooting has to go very fast or I get seriously backed up with kids that need to get to a game. The purpose of my post is to see if someone has any ideas as to why this is working when I feel as though it should not. To me the most likely reason is that the lights are firing twice since I am using them at about 1/4 power.

Ovi

Ok... if you are using the on camera flash, how is it possible to exceed the sync speed?

[OviV]

If you have a flash that can do FP you can exceed the sync speed, however, what I meant to say is that I do not want to exceed the sync speed for the Alien Bees. I know that I am safe at 1/125 so that is what I use.

Ovi