Optical flash trigger.. question
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Old 03-01-2008   #1
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Default Optical flash trigger.. question

Hello all Well I received my 'SO2' strobist kit from Mpex.com on Wednesday
and the Vivitar 285HV flash from B&H on Friday. Very happy with it all together.

But I set it all up in the backyard, about mid-morning (10:30-11:00am ish)
with my little sister all ready to pose. I planned on using my Canon 420EX
flash to trigger the 285. I figured I could "aim" the 420 so it doesn't really
affect the picture, rather it aims at the 285HV off at a angle from the subject.
But the primary reasoning on the optical trigger vs. radio (eg the V2s) was I could
only get one or the other at the time and I wanted to have two lights for indoors;
EG bounce the 420EX and still have the 285HV off the camera.

However I found that, while it works fine inside the house & garage, I cannot
trigger the 285HV while outside unless I am right on top (eg 2' away) of the
setup. However later in the evening, around dusk ish (not sure, but like 5:45pm ish??)
I was outside playing with it to my heart's content and it worked perfectly fine.
My only regret is that my little sister was abit dirty (mostly the arms 'cause she changed) from
playing with the dog. I don't think she'll want me to keep these 'hairy arms' pictures

I'm guessing the reasoning being the sensor cannot "detect" the
420EX while outdoors in a bright environment? Any help would be welcomed

MPEX Strobist SO1 Kit
^ Link to the product in question. It doesn't really give much info
on the Fotodiox Optical Hotshoe Slave. So do I need to just
bite the bullet and get a Cactus V2 wireless setup if I want to go outside?

Also, abit off topic, but does anybody have any starting
suggestions on placement of the my single light?

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Old 03-01-2008   #2
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Default Re: Optical flash trigger.. question

Are the 420 and the optical slave within "line of site" of each other? Outdoors you may need to have the slave pointed directly at the 420 because there aren't any walls/ceiling to bounce the light around to hit the slave. As the ambient light level goes down the flash is relatively brighter and then it triggers the slave.

I also assume that you have the 420EX in manual mode so that its preflash doesn't rigger the slave (or does the slave have a setting to ignore the preflash?)

I often use one light for portrait/beauty light. I place it in a small softbox (27" square) about 45-degrees between the camera and subject. Then put a reflector card on the other side to fill in some of the shadows. You can also do this with an umbrella with the flash instead of the softbox.
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Old 03-02-2008   #3
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Default Re: Optical flash trigger.. question

Quote:
I'm guessing the reasoning being the sensor cannot "detect" the
420EX while outdoors in a bright environment?
That would pretty much be my guess. The sun is just too strong for that particular flash to overcome the ambient light from a distance, or your sensor is less sensitive than others perhaps, or both.

Those things can be finicky... sometimes, even walking in front of them will trigger the flash, (shadow passes in front of sensor, then bright sun again.. FLASH!)

Having the slave's 'eye' facing towards the sun can amplify this effect too.
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Old 03-02-2008   #4
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Default Re: Optical flash trigger.. question

Quote:
Originally Posted by JohnC View Post
Are the 420 and the optical slave within "line of site" of each other? Outdoors you may need to have the slave pointed directly at the 420 because there aren't any walls/ceiling to bounce the light around to hit the slave. As the ambient light level goes down the flash is relatively brighter and then it triggers the slave.

I also assume that you have the 420EX in manual mode so that its preflash doesn't rigger the slave (or does the slave have a setting to ignore the preflash?)

I often use one light for portrait/beauty light. I place it in a small softbox (27" square) about 45-degrees between the camera and subject. Then put a reflector card on the other side to fill in some of the shadows. You can also do this with an umbrella with the flash instead of the softbox.
To clarify; the 420EX is on camera and the 285HV is the slave.
I had them both within line of sight best as possible. However, the
design on the Fotodiox is such that the sensor is looking towards the
umbrella, not opposite. So its hard to position the stand/umbrella/285HV
setup between myself and the subject, because the sensor is not looking
towards me at that point. If I put it behind the subject then I am fine.
This is irregardless if its directly behind, in front, or to a angle of the subject.

The 420EX does not have a manual mode to it It only has the option
of using it as a slave switch, buttons to set the group & channel if the
slave switch is on, the on/off switch, and a switch between normal and
high sync mode. I left the slave switch to off, and had it in normal mode.
I use the limited flash control on my XT to set the Flash Exposure Compensation
to a EV -3. I tried firing with it being anywhere from -3 to 0 EV.

To my knowledge the 420EX does not fire a pre flash... If so, I never notice.
Also the 285HV wasn't firing either way until I was right on top of the setup.
This is during the day of course. But heh, for $15 I couldn't pass a mint condt. 420EX up

Jacque - I generally am trying to shoot with the sun off to one side of the subject with the lighting
on the opposite side. So, with the design of the Fotodiox optical trigger, I am running into that problem.
The sensor is pretty much facing towards the umbrella, which being opposite of the sun...

I'm probably just going to stop buying non-vital items (soda, cigs, whichever) til payday.
Hopefully I'll be able to scrap together enough to get the V2's by then. It sucks having bills
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Old 03-02-2008   #5
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Default Re: Optical flash trigger.. question

I have one strobe with a particularly weak optical sensor, it will even stop functioning with a modeling light turned on. I solved the problem by taking a piece of foil paper and surrounding the optical slave with it making sure to have some sticking up behind the sensor to catch the flash and trigger it.

Experiment with this and you should be able to give your optical slaves sensor a little better sensitivity.
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Old 03-02-2008   #6
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Default Re: Optical flash trigger.. question

Quote:
Originally Posted by Montec View Post
I have one strobe with a particularly weak optical sensor, it will even stop functioning with a modeling light turned on. I solved the problem by taking a piece of foil paper and surrounding the optical slave with it making sure to have some sticking up behind the sensor to catch the flash and trigger it.

Experiment with this and you should be able to give your optical slaves sensor a little better sensitivity.
If I am understanding this right - then I'd basically be making a small
umbrella-shaped deal out of tin foil around the optical sensor? This
way it blocks most surrounding ambient light and has a little 'spill area'
to help catch the flash and direct it back towards the sensor?

I'm def. going to try this. I'm just hoping to have something figured out by
Monday. My best friend is going to be coming up from Orlando and after
hanging out, she usually always is willing to pose for me to try out new ideas
and equipment, etc.
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Old 03-02-2008   #7
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Default Re: Optical flash trigger.. question

Yup...worked for me. Good Luck.

Use the shiny side up
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Old 03-02-2008   #8
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Default Re: Optical flash trigger.. question

Quote:
Jacque - I generally am trying to shoot with the sun off to one side of the subject with the lighting on the opposite side. So, with the design of the Fotodiox optical trigger, I am running into that problem. The sensor is pretty much facing towards the umbrella, which being opposite of the sun...
Try taping a piece of aluminum foil over the optical sensor, facing towards where your triggering flash is firing from. Like making a cup around 1/2 of the sensor, and sticking up past it an inch or two.

This is just helping to mirror the triggering flashes' light, iow, creating a specular highlight close to the optical slave.
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Old 03-02-2008   #9
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Default Re: Optical flash trigger.. question

Hmmm, I need to refresh the page before replying! lol

Montec's got it right!
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Old 03-02-2008   #10
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Default Re: Optical flash trigger.. question

I'm not sure if I did this right.. can't test until tomorrow.
Anybody have a picture of this on hand?


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