Posted by
Kenneth Sloan-2 on
Sep 05, 2013; 1:33pm
URL: http://imagej.273.s1.nabble.com/HELP-needed-from-IMAGEJ-to-Photoshop-tp5004584p5004667.html
Lots of interesting (and perhaps debatable points), but I think this response misses the main point.
The OP has an RGB image and exports it in TIFF. He is confused when he views the individual channels and Photoshop displays them as gray-scale.
The answer is: when you split the RGB image into three separate 1-channel images, you no longer have "color" images. Each individual channel is a scalar image, which Photoshop will display as
gray-scale, by default.
If you want to display the R channel as a collection of shades of red, then you need to either:
a) export 3 RGB images - after first ZEROING the channels you don't want to see. ZEROING the (say) G and B channels is not the same as REMOVING them. REMOVING the G and B channels gives you a gray-scale image. ZEROing those channels gives you an RGB image where all of the colors are shades of R
OR…
b) use Photoshop tools (sorry, my fingers don't do Photoshop so I can't give specific button pushes - but I'm sure this is easy) to convert each 1-channel image back into a color image. One perfectly reasonable way to do that is to define a Color LUT that converts scalars to colors. Use one LUT to make the R channel RED, another to make the B channel BLUE, and a third to make the G channel GREEN.
This may only be feasible if you have 8-bit images. [aside: nearly 40 years ago I was happily doing all of this with 12-bit LUT's, but then the industry appeared to take a giant step backwards and has only recently started to recover…but I digress]
--
Kenneth Sloan
[hidden email]
On Sep 5, 2013, at 07:03 , Johannes Schindelin <
[hidden email]> wrote:
> Dear balloon02,
>
> On Tue, 27 Aug 2013, balloo02 . wrote:
>
>> Hi, I am in dire need of help with converting imagej files that are
>> saved as TIFF files to viewing them in Photoshop. In IMAGEJ, my images
>> have 3 separate channels (blue, red, green). My problem is that when I
>> view the split images in photoshop they are gre,. Instead of my split
>> images being blue, red, or green like when I saved them as TIFF files
>> from IMAGEJ they are now grey. Furthermore, when I open those same files
>> "turned" grey back in image they are now grey instead of being their
>> original color (blue red or green). Can someone please help? Thank you
>
> Please note that the red/green/blue visualization of scientific images is
> just a compromise, mostly for historical reasons. Scientific images are
> usually multi-channel, and visualizing them as RGB is actually wrong:
> imagine an image of green fluorescent cells, the first channel
> representing a range of wavelengths -- smooshing them all into the same
> green is obiously incorrect, I hope you agree. Worse: the vast majority of
> computer screens is not calibrated, so it depends on the screen *which*
> wrong green you see.
>
> Further, the pixel values stored in scientific images are typically *not*
> intensities as in photographs. See
>
http://www.4p8.com/eric.brasseur/gamma.html for the very real implications
> of this issue.
>
> And then there is also the issue of human vision: our color vision is
> simply not very precise (as you can easily verify yourself at dusk: you
> see gray with only minimal color).
>
> Assuming that you want to present your multi-channel data to others, I
> would therefore *strongly* suggest to keep the images in grayscale, but
> color their labels. That way, you have a clear representation with minimal
> information loss.
>
> Ciao,
> Johannes
>
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