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Dear Judy: They use a formula to convert RGB to gray intensities. I am
not sure what this formula is, but it takes into account weighted
contributions from each channel. So if you have pure red (255) and
nothing else in an RGB image and convert it into an 8-bit gray you get
an intensity not 255 but only 85 (which tells you, by the way, the Red
comes with coefficient 0.3).

Michael Model, Ph.D.
Confocal Microscopy Core
Dpt. Biological Sciences
Kent State University
Kent, OH 44242
tel. 330-672-2874

-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]] On
Behalf Of Judy Trogadis
Sent: Monday, April 07, 2008 11:03 AM
To: [log in to unmask]
Subject: image processing

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I have a simple question, related to an annoying problem.

I have an image of a multilabelled fluorescent specimen, displayed as a
merged RGB image. I would like to analyze just the red channel, so I
split the channels and obtain B & W images of the individual component.
They all look as bright as the original.

However, if I only have a single red image and would like to convert it
to a B & W image (change mode RGB to grey), for 8-bit analysis in
ImageJ, for example, the resulting image is very dull and fainter.
Furthermore, this effect is much more dramatic with a red image than
with a green image.

What is happening? 
Thanks,
Judy


Judy Trogadis
Bio-Imaging Coordinator
St. Michael's Hospital, 7Queen
30 Bond St.
Toronto, ON M5B 1W8, Canada
ph:  416-864-6060  x6337
pager: 416-685-9219
fax: 416-864-6043
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