Underground Photographs

[JohnAber]

Hi,

I'd apprecite some advice on digital cameras for underground photography in a mine (geological photos of the rocks). Essentially almost completely dark apart from minor artificial light (torches etc). I have been using a Canon Powershot A70 with very good results using Auto but the flash is limited to about 3m (depending on rock colouration etc).

What I want is something as easy to use, ideally without a separate flash unit, just a Camera with a more powerful flash that I can take lots of shots without any hassle.

I have also had reasonable results with an older Canon Powershot Pro 70 and a Speedlite 380X although this is a more clumsy arrangement and the photographs are often out of focus (but lighting is better).

Any recommendations or relevant links much appreciated !

[RockOne]

G'Day.
On the Canon website the flash ranges for each model camera are listed under the specifications.
They are also listed under the specifications in the camera reviews at http://www.dpreview.com/

Good luck with your search

[PhotosGuy]

Those underground rocks are going to soak up a LOT of light! Also consider that the light from the flash will be uneven close up.
Lighting ratios:
1 light at 5.6' & another at 8' = 1-stop difference = 2X the light.
1 light at 5.6' & another at 11' = 2-stops difference = 4X the light.
See the relationship between f-stops as numbers & f-stops as a measure of distance?
So, if you can, you'll get more even light on the entire frame if you can shoot at maybe 20 feet since the light fall-off will only be 1-stop from 16 feet to 22' & 1-stop from 22' to 32'.
Personally, if I was doing it, I'd use the on-cam flash as a "fill" & use a slave flash to kick some light in from an angle at the side something like the pic I posted at:
http://photography-on-the.net/forum/showthread.php?t=61228
Just to jazz things up a bit, you might play around with a colored gell on the side light.