Sunday, November 13, 2005

Dress & Jeans

Well, not really a dress, but the shape of the duvet triggered this idea. The jeans were added to the scene to compliment and add an interesting juxtaposition. Technically, this was based on some attempts to recreate multiple exposures, digitally. I first tried to follow the recipe in the Freeman Patterson books, where for a 9 exposure image you want to underexpose each image by 3 stops [ sqrt(9) ]. I then recreated the multiple exposure on a single frame using the screen layering mode in Photoshop. This seemed to give a fundamentally good exposure, but the problem is that a -3 EV exposure on digital has a huge amount of noise, because almost all of the exposure is in the noisy, low detail shadow area. So I took a different tack - taking 9 images at the original exposure, getting as much information in to the RAW file as possible. I then used the RAW converter in Adobe Bridge to underexpose each image digitally by 3 stops. This way there is a whole lot more information and a whole lot less noise in the final images. I then re-layered and screened the images in Photoshop to get the result above. I think I still need to look in to the correct exposures and blending modes but this approach, using RAW mode capture, seems to be the right way to go. I don't have a similarly good idea for JPEG shooting, though something roughly equivalent might be possible using the Image Menu, Exposure option and shooting the JPEGs at a normal exposure level, then dialing down to the appropriate level prior to layering. Something that might be worth exploring, given digital's better performance in the highlight area, below blown highlights, might be trying to emulate sandwiches of multiple slides, where each image is over-exposed and then combined using the multiply blending mode. This way of over exposing and blending might well be worth a look anyway - something somewhat similar for exposure vs. frames would make sense, except over expose by sqrt(frames) rather than underexpose. Probably would be very difficult to get away with more than 4 or 5 frames though, without losing almost all the highlights - again shooting in RAW at a normal exposure and then brightening might work - but there is increased noise going that way for a RAW file. Next thing I want to do is to come up with a script that will do some of this automagically straight from Bridge. Any thoughts and suggestions would be extremely valuable right now!


AJAger said...

I was thinking about this very matter today and I feel that this is where digital really scores. Using slide film, one has to consider the amount to overexpose by before layering. Using film, one has to underexpose before multiple-exposing. I feel that both these methods can be very closely approximated by layering of normally-exposed digital shots in post-processing, so no soul-searching has to be gone through while shooting.