Digital Cameras and Long Exposure Times:
Noise and Dark Current Comparisons
http://www.clarkvision.com/articles/long-exposure-comparisons
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How well do digital cameras perform during long exposures? On this web page, I'll
show the details on digital camera dark current and compare some
different sensors.
Figure 1a. A Canon 1D Mark II 5-minute dark exposure at ISO 800.
Processing: standard curve raw conversion with default settings.
Figure 1b. A Canon 1D Mark II 5-minute dark exposure at ISO 800.
Processing: standard curve raw conversion with default settings from Figure 1a,
then scaled 0 to 10 DN in Photoshop using levels (this multiplies
the image data by 25.5).
Figure 2a. A Nikon D50 5-minute dark exposure at ISO 800.
Processing: standard curve raw conversion with default settings.
Figure 2b. A Nikon D50 5-minute dark exposure at ISO 800.
Processing: standard curve raw conversion with default settings from Figure 2a,
then scaled 0 to 10 DN in Photoshop using levels (this multiplies
the image data by 25.5).
Figure 3. A Canon 1D Mark II 5-minute dark exposure at ISO 800
is compared to a Nikon D50 dark under the same conditions.
Processing: standard curve raw conversion with default settings
then scaled 0 to 10 DN in Photoshop using levels (this multiplies
the image data by 25.5).
References
Night and Low Light Photography with Digital Cameras
1)
CCD Gain. http://spiff.rit.edu/classes/phys559/lectures/gain/gain.html
2)
Charge coupled CMOS and hybrid detector arrays
http://huhepl.harvard.edu/~LSST/general/Janesick_paper_2003.pdf
3)
Canon EOS 20D vs Canon EOS 10D and
Canon 10D / Canon 20D / Nikon D70 / Audine comparison
http://www.astrosurf.org/buil/20d/20dvs10d.htm
4)
http://www.photomet.com/library_enc_fwcapacity.shtml
5)
Astrophotography Signal-to-Noise with a Canon 10D Camera
http://www.clarkvision.com/astro/canon-10d-signal-to-noise
Notes:
DN is "Data Number." That is the number in the file for each
pixel. I'm quoting the luminance level (although red, green
and blue are almost the same in the cases I cited).
16-bit signed integer: -32768 to +32767
16-bit unsigned integer: 0 to 65535
Photoshop uses signed integers, but the 16-bit tiff is
unsigned integer (correctly read by ImagesPlus).
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First published September 1, 2006.
Last updated September 6, 2006