Slave flash unit?

[Fat Tone]

I've been asked to take some formal group photographs.

My camera is the Panasonic TZ65, and I have a tripod.

Would it be possible to improve the lighting with this:

http://www.amazon.co.uk/gp/product/B001B078EY/sr=8-11/qid=1287308665/ref=olp_product_details?ie=UTF8&me=&qid=1287308665&sr=8-11&seller=

Thanks,

Tony.

[VJ]

I don't know the camera, but I assume you want to trigger the remote flash using the camera's flash.
Theoretically that should work.

There is one danger: flashes that are remotely triggered by other flashes could be set off by by the camera's pre-flashes (most camera's fire a sequence to measure proper lighting, IIRC, my D100 fires 3 sequences of 3 flashes each). If this is the case and the remote flash doesn't recycle quickly enough, it might not be ready to fire on time. My Nikon SB800 has a built in SU-4 function (which triggers it via another flash), and while I read this warning on forums, I had no problems with triggering it from several cameras.
But I guess it is unlikely to occur (the studio flash seem to be plugged in rather than battery powered, and the preflashes are not as bright as the real one). FWIW, if it occurs, you can circumvent it by either using a slightly longer shutterspeed or using manual mode on the camera (this should turn off any preflashes).

If you use it, take care of orienting the light sensor properly and not blocking it, otherwise you may have some intermittent failures.

[VJ]

Oh, one more thing: look up the spread of the lightsource... it may be too narrow (e.g. more aimed at shooting single person portraits or product photos).

FWIW, flash photography is difficult; with one lightsource you may have shadows appear... So the backdrop might be important as well.

(I should add that I've ever used such things, my knowledge is mainly theoretical and from experience with my own external flash unit)

[Fat Tone]

Thanks VJ.

The camera flash, if not using anti red-eye, seems to do a weak flash followed immediately by a strong flash. I do seem to have manual modes to set exposure and ISO. Presumably I would need to reduce exposure to allow for the extra flash?

I wonder if I am over complicating things and should just stick to the camera's flash. It's not the strongest in the world but not too bad, and they have been warned!

[VJ]

I'm not sure you need to reduce exposure. It depends really on the camera and how it determined the exposure... On mine, I didn't need to adjust for it.

For sure, it will be making things more complicated (but the sound of a flash light recycling is cool ), I just wonder if it is not feasible with present ambient lighting or simple spots? Oh, also check the white balance, once you start using additional light sources, it becomes more tricky. Either test with several settings, or use custom white balance if available.

[Fat Tone]

Well I do have access to a couple of video lights that will add quite a bit of constant light. Perhaps that would be sufficient.

Regarding exposure, surely if it does its light metering and then there's a whole lot more light when it takes the shot it would be over-exposed? Or is the amount of light added not actually that significant?

[VJ]

It depends on some factors.
I know many DSLRs are capable of adjusting exposure based on the pre flashes. So if the slave flash fires together with the preflash, and it recycles quickly enough to also flash with the main flash, exposure will have been compensated correclty. I know the Nikon F5 (top model analog) was even capable of doing some adjusting DURING the flash (which is crazy if you consider that the duration of the flash is so brief - but adjustable on advanced flash units).
For compact cameras, it is possible that the metering system knows the flash will fire, but does not take into account the actual range of the flash light (and the camera may not know the distance to the subject). So it will meter under the assumption that the subject is within flash range. When you start adding more lights, you commonly do this to illuminate objects outside of the flash range. So these areas would have been to dark under the assumed exposure anyway.

There are many more scenarios in which it may not matter (fill flash: scene is bright anyway, spotmetering in a different location, ...).

[Fat Tone]

I'm off the hook. They've got someone who enjoys this sort of thing and has a good track record.

I'm tempted to have a play with this at some point anyway, so I can do a better job of home portraits etc.

Many thanks for all your thoughts.

T.

[VJ]

Only recommendation if you get an external flash unit: get a GOOD one that properly works with your camera.
The use of digital camera's has forced manufacturers to change flash metering systems (mainly due to the different reflection of the light off the imaging sensor compared to the reflection of off a film - is this grammatically correct? ). So in the early days the systems were quite proprietary, now I think the flash manufacturers (Metz, ...) have adapted to the new camera manufacturers' systems.

The problem with flash photography is making the photo look as if no flash was used. And the flash units are quite expensive for something you'd rather not use due to the complexity.