White balance lens cap for Pre-Exposure

**Lachlan 717** · 7-Jan-2010, 15:52

Has anyone tried one of these (see eBay listing 220535479121) digital white balance lens caps for pre-exposure?

I'm not sure how light tight the seal would be, but it might be worth a sheet or 2 to test.

**D. Bryant** · 7-Jan-2010, 20:30

Originally Posted by Lachlan 617

Has anyone tried one of these (see eBay listing 220535479121) digital white balance lens caps for pre-exposure?

I'm not sure how light tight the seal would be, but it might be worth a sheet or 2 to test.

I've not used one myself but have considered it also. I think it has interesting possibilities.

Don Bryant

**Lachlan 717** · 7-Jan-2010, 21:00

Originally Posted by D. Bryant

I've not used one myself but have considered it also. I think it has interesting possibilities.

Don Bryant

I think that the seal could be a problem, but a strip of 3mm neoprene and some adhesive could make a light-tight sleave.

Also, I don't know if the circle of white is big enough to cover the whole image. No good if it vignettes.

Maybe kill 2 birds and glue one to a step-up ring, and then attach the neoprene?

**Lynn Jones** · 11-Jan-2010, 13:43

I've tried several of these that didn't work including a couple that I made. The light source muse be very even. I finally ended up exposing out of focus grey cards in the studio and marking the holders. For certain applications I sometimes pre-expose wit colored filters, but that is another story.

Lynn

**Lachlan 717** · 11-Jan-2010, 15:54

Originally Posted by Lynn Jones

I've tried several of these that didn't work including a couple that I made. The light source muse be very even. I finally ended up exposing out of focus grey cards in the studio and marking the holders. For certain applications I sometimes pre-expose wit colored filters, but that is another story.

Lynn

Thanks for the info, Lynn.

What caused the lack of uniformity? Was it a light leak?