Quote:
Originally Posted by pmrid
At the risk of asking a silly question, can you achieve a similar result by setting the camera to shoot in B&W mode?
Peter
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Hi Peter,
there are lengthy explanations for this, but the simplistic answer from my understanding is that it won't provide the same sensitivity.
below is just my understanding, I'm no expert though.
B&W or mono images from a colour camera use interpolated values for luminosity. that is bright and dark areas.
this doesn't change the fact that red light will get through only one of the 4 pixels due to the colour filter array above the sensor, similarly blue will enter only the pixel with the blue filter.
by removing the CFA, all wavelengths reach the four pixels and hence provides higher sensitivity and resolution.
That's the reason mono CCD's with LRGB images have more detail in them.
as you may know, with mono imaging, its the "L" channel that carries all the details.
This CFA mod appealed to me because I could use a relatively large sized chip for mono imaging at a fraction of the cost, compromise is the lower QE, noise, and lower dynamic range compared to astro CCD's.
it also allows you to do narrowband imaging using the full resolution of the chip. I've done Ha imaging with an OSC, and I can only use the red channel. so a 11M image becomes a 3M image as its only 1/4th the data.
with the 350d now being mono, I can use all pixels for Ha or other NB.
Edit: the company maxmax which also does BW conversions have a very good write-up here with example images clearly showing the difference.
http://www.maxmax.com/b&w_conversion.htm
They do sell B&W dslr's but for that price, you could get a mono ccd.
i'll post my own results a little later on.
Cheers
Alistair