Tuesday, 3 June 2008
I have been pretty dissatisfied with long exposures using the digital camera. Anything past about 10-15s leads to horrid noise or detail loss with black frame removal. Plus a stack of filters seems to degrade the image more than film (or maybe that's just me).
Anyway, while processing the above image, I tried something different. I'd taken about 6 exposures of the scene with exposures varying from 1/3 to 1s. I was trying to get a smooth flow to the stream of water on the right. I only had a 2 stop ND filter, which didn't help. Looking through all the exposures I was considering pasting together parts from each to get the effect.
I then turned to Photomatix Pro to blend all 6. Not HDR, though. I just used the average function and some slight tone mapping. What a huge difference, seen here:
Total exposure time for the 6 images was about 5s. The overall result though is of a much longer exposure. There is some great effect from the smaller flows amongst the rocks (100% crop below). Plus noise is gone and detail is great, something Photomatix is really good at.
So there it is: take a whole lot of relatively short exposures and average the results. Output resembles a longer exposure than the sum of the parts.
I've not tried this yet with some really short exposures, but that would be fun. Say 10 or more at action freezing speeds (1/125 and faster).
Oh, and before you all chip in, I realise there were a bunch of film based techniques similar to this but I've not come across something similar in the digital world.