Slave Flash Photography

[Ikinaa]

Here's what I got :
a G3, Speedlite 380EX, Speedlite 155 and Hama Slave adapter
(I know, a G3 is no DSLR, but my question is about slave flash and I guess, people in here using DSLR can more help me than in the P&S)
First try : G3 + 380 firing, 155 fires also, picture is something near white (overexposed)
Second try : G3 + 380 + *-button, little 380 flash, measures exposure, 155 no flash, then take shoot, 380 + 155 fire, picture seems ok to me (histogram seems nice)
Ok... as far as I understand, when pressing the *-button, the cam fires the flash for measuring exposure, and stores the values), but how does the 155 do that? Ok it's got a measure cell (do you call it like that), and how does the 155 know I sent a preflash for measuring, or does the 155 simply measure, keep the settings for some time and uses them fire the flash for the true photo. if yes, how long does it keep the settings? if no, anyone can explain?
Thanks a lot

[scottbergerphoto]

The setup you are using doesn't provide for any wireless control of flash output. I'm not familiar with the 380EX , but since it is an EX flash, it shoots in ETTL unless you have it set to manual if that's an option. The preflash from the 380EX will determine its own flash output. Unless you have a DIGITAl slave attached to your slave flash, it will be fired by the pre flash and not the actual flash. Assuming that you have your speedlite 155 attached to a digital slave, you would have to set its output manually. So you would have one flash(380EX) controlled by ETTL setting off another slave flash that is set manually. I don't know how this could result in good exposure as the 380EX output is being based on a reading taken with only itself firing. Then both flashes go off and and you have more light then you need. You can't even manually meter this set up as when you take a handheld meter reading and set the camera, the output will change again wth the new preflash. It seems to me that you need to use all flashes linked wirelessly ETTL such as with the 550EX and 420EX, or all flashes set to manual and metered with a flash meter.
Scott

[DaveG]

scottbergerphoto wrote:
The setup you are using doesn't provide for any wireless control of flash output. I'm not familiar with the 380EX , but since it is an EX flash, it shoots in ETTL unless you have it set to manual if that's an option. The preflash from the 380EX will determine its own flash output. Unless you have a DIGITAl slave attached to your slave flash, it will be fired by the pre flash and not the actual flash. Assuming that you have your speedlite 155 attached to a digital slave, you would have to set its output manually. So you would have one flash(380EX) controlled by ETTL setting off another slave flash that is set manually. I don't know how this could result in good exposure as the 380EX output is being based on a reading taken with only itself firing. Then both flashes go off and and you have more light then you need. You can't even manually meter this set up as when you take a handheld meter reading and set the camera, the output will change again wth the new preflash. It seems to me that you need to use all flashes linked wirelessly ETTL such as with the 550EX and 420EX, or all flashes set to manual and metered with a flash meter.
Scott

I also thnk that you'll need a camera that supports the wireless TTL. Even older Canon cameras like the A2E won't. So I sort of doubt that the G3 will, unless it specifically says so in its instruction book.

[scottbergerphoto]

DaveG wrote:
scottbergerphoto wrote:
The setup you are using doesn't provide for any wireless control of flash output. I'm not familiar with the 380EX , but since it is an EX flash, it shoots in ETTL unless you have it set to manual if that's an option. The preflash from the 380EX will determine its own flash output. Unless you have a DIGITAl slave attached to your slave flash, it will be fired by the pre flash and not the actual flash. Assuming that you have your speedlite 155 attached to a digital slave, you would have to set its output manually. So you would have one flash(380EX) controlled by ETTL setting off another slave flash that is set manually. I don't know how this could result in good exposure as the 380EX output is being based on a reading taken with only itself firing. Then both flashes go off and and you have more light then you need. You can't even manually meter this set up as when you take a handheld meter reading and set the camera, the output will change again wth the new preflash. It seems to me that you need to use all flashes linked wirelessly ETTL such as with the 550EX and 420EX, or all flashes set to manual and metered with a flash meter.
Scott

I also thnk that you'll need a camera that supports the wireless TTL. Even older Canon cameras like the A2E won't. So I sort of doubt that the G3 will, unless it specifically says so in its instruction book.

The G2 is an "A" Type Body, as is the D30,D60 and 10D. All A type bodies using ETTL function with wireless TTL with the 550EX. I don't see why the G3 shouldn't work as well.
Scott

[Ikinaa]

scottbergerphoto wrote:
The setup you are using doesn't provide for any wireless control of flash output. I'm not familiar with the 380EX , but since it is an EX flash, it shoots in ETTL unless you have it set to manual if that's an option. The preflash from the 380EX will determine its own flash output. Unless you have a DIGITAl slave attached to your slave flash, it will be fired by the pre flash and not the actual flash. Assuming that you have your speedlite 155 attached to a digital slave, you would have to set its output manually. So you would have one flash(380EX) controlled by ETTL setting off another slave flash that is set manually. I don't know how this could result in good exposure as the 380EX output is being based on a reading taken with only itself firing. Then both flashes go off and and you have more light then you need. You can't even manually meter this set up as when you take a handheld meter reading and set the camera, the output will change again wth the new preflash. It seems to me that you need to use all flashes linked wirelessly ETTL such as with the 550EX and 420EX, or all flashes set to manual and metered with a flash meter.
Scott

Thanks for your answer, I don't either understand how it works, but when I shoot without preflash, the picture is really really overexposed. With preflash (the 155 not firing), then shooting (both are firing), the picture is well exposed, I tried it on several occasions, it always worked the same... the photoshop guy who sold me the slave adapter told me to get an old flash that has a measuring cell on it to use it (the 155 has one, it's from 1978, newer flashes don't have one), so that it should work, with newer flashes without the measuring unit, there could be problems.