How do you set up a flash for UV photography ?

[colinbm]

How do you set up a flash for UV photography ?

I have been trying to learn flash photography, & getting some success with a normal visible light camera & auto lens with the flash set up for TTL.

I am not having much success with manual flash on manual lenses ?

Any help gladly received please. I am using a Godox AD200.

[nfoto]

You will need to put the flash on manual. If the setup allows your putting the flash close to the subject, that is to at least to be tested. However, the downside is you might need additional reflectors to avoid black shadows.

 

Run a test shot of something familiar in terms of UV reflectiviity with the flash at max. output, a medium low ISO setting (say 200) on camera, and your lens set to wide open and fitted with a suitable UV bandpass filter. Fire away. If you get a totally blown-out picture that's good as it means you have sufficient UV output to allow stopping your lens down and/or cut back on the flash output. If so and the flash maximum is M1/1, try M1/2, M1/4, ... until the blown-out impression is reduced. Then you can experiment with stopping down the lens (you might increase flash power again, through).

 

When your setup delivers exposures in the ballpark of anything useful, you can apply it to some real subjects.

[nfoto]

A further notice can be helpful: at close range, most flash reflectors become very inefficient to cause a significant light loss compared to what one would expect. Thus there is an intermediate distance range in which the practical resulting exposure is largely similar hence the "law of reciprocal distance" fails.

 

Do avoid bare-bulb flash for close-ups, however, unless you work with a light-tent setup. Bare-bulb is incredibly inefficient up close.

 

Wide-angle reflectors function the better for my studio flashes when distance to subject gets closer to 1m. They are so powerful that I hardly need to put them any closer. Thus I can avoid the significant heat blast associated with flash output. Many subjects, such as flowers, will wilt or start to move when subjected to repeated flashes in the near range.

 

A final advice: use UV goggles all the time. You can really hurt your eyes if you experiment with UV flash photography and leave your eyes unprotected.

[ulf]

You will need to put the flash on manual. If the setup allows your putting the flash close to the subject, that is to at least to be tested. However, the downside is you might need additional reflectors to avoid black shadows.

 

Run a test shot of something familiar in terms of UV reflectiviity with the flash at max. output, a medium low ISO setting (say 200) on camera, and your lens set to wide open and fitted with a suitable UV bandpass filter. Fire away. If you get a totally blown-out picture that's good as it means you have sufficient UV output to allow stopping your lens down and/or cut back on the flash output. If so and the flash maximum is M1/1, try M1/2, M1/4, ... until the blown-out impression is reduced. Then you can experiment with stopping down the lens (you might increase flash power again, through).

 

When your setup delivers exposures in the ballpark of anything useful, you can apply it to some real subjects.

I concur.

This is similar to how I use my two AD200, except that I start with the lens stopped down suitably from the start.

For stacking aiming at optimal resolution, for single shots, aiming at some DOF I want to get.

 

As I am using two flashes I first find a working distance/placement for a good contrast balance, without too much shadows, and then change the common manual power on the remote radio trigger device, sitting on the camera.

I have to change the power for each filter stack type I want to use and start with the lowest power setting for the vis image with a BG38 only, on the lens. If possible I like to shoot with ISO100 in the beginning to minimise any noise.

After some time with this I have learned approximate power settings for each stack type.

[colinbm]

Thank you both, Birna & Ulf, I will try this out today & see how I progress.