Flash techniques; Eliminating the Carapace Burn/Overexposure?

l2oBiN

Hi all,

I have found that highly reflective surfaces such as carapaces from hoverflies tend to show a distinctive burning out/overexposure even with diffused flash.:scratch Has anyone come up with anything that oversomes this? A couple of examples?

Robbug

I am no expert here, but if I recall correctly, diffuse flash works like a charm. I just did a DIY diffusing flash setup using the camera's built in flash and the lighting is quite nice. Try to soften the light.

Rob

Edit: maybe I should read the post more thoroughly next time. Disregard everything above Sorry about that. Maybe off axis flash?

Lord Vetinari

It is a common problem. Good diffusion on a flash will help stop these reflective spots actually burning out but does not stop them being present. In natural light you can stop them a bit with a polariser but this does not really work with flash unless you polarise the flash as well and end up losing around 4 stops of light or more. see article here http://www.naturescapes.net/042004/wh0404.htm
The only other way of at least reducing them with flash is to vary the flash/lens angle- ie alter the flash angle with respect to the subject and lens so bright reflections do not go straight back in the lens.
As long as the bright spots are not too large and are not burned out I do not find them objectionable- they just tell you the subject is shiny. The double polarisation technique I mentioned above actually gives very unnatural looking shoots.

Example shot on a ladybird which has a bright reflection but it is not actually blown.

Brian V.



[EDIT] Shooting against a paleish reflective/light scattering background can also help reduce the intensity of reflections by reducing the flash output even though I had to use +ve FEC to the exposure correct.

l2oBiN

Lord Vetinari wrote:

It is a common problem. Good diffusion on a flash will help stop these reflective spots actually burning out but does not stop them being present. In natural light you can stop them a bit with a polariser but this does not really work with flash unless you polarise the flash as well and end up losing around 4 stops of light or more.
The only other way of at least reducing them with flash is to vary the flash/lens angle- ie alter the flash angle with respect to the subject and lens so bright reflections do not go straight back in the lens.
As long as the bright spots are not too large and are not burned out I do not find them objectionable- they just tell you the subject is shiny. The double polarisation technique I mentioned above actually gives very unnatural looking shoots.

Example shot on a ladybird which has a bright reflection but it is not actually blown.

Brian V.

Hmm, I think its black shiny that is the biggest problem because the flash overcompensates, perhaps I should try spot metering. By the way Brian, have you tried using a slightly yellow tissue to give it a more natural sunlight cast? I have been thinking on how to make it look slightly more sunlight like.

Lord Vetinari

l2oBiN wrote:

Hmm, I think its black shiny that is the biggest problem because the flash overcompensates, perhaps I should try spot metering. By the way Brian, have you tried using a slightly yellow tissue to give it a more natural sunlight cast? I have been thinking on how to make it look slightly more sunlight like.

With metering - not sure what your camera does but canon cameras default to pattern metering when flash is used. I judge the exposure using the background- light backgrounds need +ve FEC and dark backgrounds -ve FEC.
WRT colour I actually do colour temp adjust my flash shots to give the same colour balance I see in the viewfinder- I actually don't like the warm tint that canon flash tends to deliver

Brian v.

l2oBiN

Lord Vetinari wrote:

With metering - not sure what your camera does but canon cameras default to pattern metering when flash is used. I judge the exposure using the background- light backgrounds need +ve FEC and dark backgrounds -ve FEC.
WRT colour I actually do colour temp adjust my flash shots to give the same colour balance I see in the viewfinder- I actually don't like the warm tint that canon flash tends to deliver

Brian v.

Brian have you tried the double polariser? If so, could you post a couple of examples?

Lord Vetinari

l2oBiN wrote:

Brian have you tried the double polariser? If so, could you post a couple of examples?

Not successfully- I tried using actual polaroid sunglasses and lost too much light - there were a couple of examples in the link I gave.
Brian v.