"Medusa Revisited" by Ben Heaven (c) 2008
[Another wonderful image by the English Nocturnal Photographer Ben Heaven. Here, in his own words, is how he made this digital photograph.]
I shot this with my D200 which has pretty poor battery life. However there is a popular technique to remove noise that I adapted to deal with the battery issue. The technique works like this; you use a remote release with a timer (or lock down the release shooting 30 second exposures) so that you take multiple shots for the entire length of the exposure rather than one single long shot. You need to make sure there is almost no delay between shots. At the end you take an additional frame of the same period as one of the single frames, with the lens cap on. This is the 'dark frame' that you use to subtract noise from your stack of images. Using this technique you don't need to include a 'noise reduction' stage in the camera that often takes 1/2 as long again (or sometimes the total time of the exposure). You use software to combine your stack of images into a single file. I find with the D200 I can only get about 80 minutes total from a single battery, but with the stacking method, if I'm quick I can swap the old battery with a fresh one and just keep stacking!
OK, here are the specifics on this shot:
D200, ISO 100, 24 exposures of 5 minutes duration @ f5.6, 10mm. Tree painted for 2 minutes at ISO 400 and the image overlaid in PhotoShop. Processed with DXO film pack to resemble Acros 100, Terra Sepia Tone 'printed' at grade 3.
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