It seems I set a bit of a cart rolling with my comments about the
necessary bit-depth of CCD cameras... so two final comments from me!

(1) I fully agree with Ted and Hans et al about the necessity for around
12 bits B&W for optimal acquisition of images that match human
perception, to optimise what you can do with image processing, and so
on. Indeed, we do already use a cooled CCD at 12bits for acquiring
certain images of living tissues, where there is a large range of
intensities with a largely unpredictable and uncontrollable intrinsic
image contrast, and where we do a lot of post-acquisition image maths.
Also we are getting another 12bit cooled CCD for using on our
fluorescence microscopes for those times when 6bits clearly are not
enough, or when the signal to noise is too high for decent imaging with
our cheap cameras.

(2) However, despite all that, when it comes to the crunch and you are
preparing images of fluorescence labelled cells for publication, the
amount of contrast gradation that is usually required is next to
nothing. I'd reckon most fluorescent images that are published would be
lucky to have more than about 8 effective grey scale levels in total!
Certainly back in the darkroom days, how often did you push your prints
using grade 4 or 5 paper to maximise the "contrast"? [I even knew of
people who used litho paper to get the analogue equivalent of binary
images of their fluorescence pix, and used them in publications...
(though I am definitely not advocating that you can get away with 1-bit
imaging!!)] And this is allowing for the inevitable loss of contrast
associated with the final reproduction process in the journals. So I
still think, that, in many cases, you can get excellent publication
quality pictures of fluorescence labelled cells with very cheap
systems...

Finally, I have just heard that there is a cheap Panasonic B&W CCD
camera (About A$1200 = <US$1000) that is supposed to have on-chip
integration and greatly outperforms the Sony ones that we use. We will
be testing one soon, and I'll let the list know how it performs as soon
as we know!

Phew! I hope that helps...

IAN




--
Professor Ian Gibbins
Anatomy & Histology
Flinders University of South Australia
GPO Box 2100, Adelaide, SA 5001
Australia

Phone:  +61-8-8204 5271
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