How to photograph an ice cave?

[Sean Setters]

Actually, a flash would be perfect. In fact, I'd suggest doing long exposures just like you said. While the camera's shutter is tripped, use the flash handheld and walk the flash around popping it at as many things within the frame as you can. Basically, you'd be turning one flash into many flashes. You'll probably be using the flash at 1/16 power or below in order to maximize the amount of flashes you can use within the shutter's duration. Just make sure that you aren't blocking the area that's getting flashed at any point and time (else, you'll record yourself in the image).

I used a similar technique to photograph this car. We only had 3 flashes, but we combined three different shots (moving the flashes around) to create the final image with 7 separate flash pops.


Dodge Challenger [Anamorphic Widescreen] by budrowilson, on Flickr

You could basically do the same thing, except move the flash around while the shutter is open and have it all done in-camera. However, you will need to have a clear understranding of the area you're working in because you can't be using your headlamp while doing it. Therefore, you'll need to map out your path and know exactly where the obstacles are before doing it.

Of course, the other alternative is to do several individual shots and combine them in post as I did. If you do that, it's easy enough to lay each image on top of the other using the "Lighten" blend mode to bring out the illuminated area of each image.