Posted: Sat Feb 12, 2011 3:14 pm Post subject: Path selection question for an image of neurons
I have a photo of neurons taken by a microscope as a TIFF. I'd like to remove the black background color and any "cloudiness" that appears in the photo but still maintain the detail of the neurons and the connections. Essentially, I'd like to change the color of the neuron related pieces to something other than red. I'd also like to pick up most of the detail in the photo that relates to the neuron without taking along any of the black background (see image attachment).
I addition I'd want to be able to set the neurons on a different color background that's solid and not murky. I just upgraded my version of Photoshop from CS2 to CS5 and definitely noticed a difference in its ability to pick up the paths. I don't know if I'm being too demanding of Photoshop or if I'm not getting the result I want because there's a better approach. I would greatly appreciate any suggestions on how to go about doing this.
Thank you!
Karen
neurons_bkgremoved.jpg
Description:
I tried selecting a path with the color selection tool (taking just the reds) and copying it on to a new layer but as you can see, some of the detail was lost and the edges are picking up some of the black background
The picture is all red which is where problems are starting from.
Levels or curves can be adjusted to change the deepest red colour to true black.
This causes a depth issue, where the duller links between the neurons that are close to the background colour will fade away.
This is the same reason why you have ended up with black in your attempt, because its actually dark red within the selection threshold.
Also the links change shade, so techniques that involves the type of automatic selection which photoshop uses could cause gaps in the links where they become to dark.
Once that has been sorted...
Colour can easily be changed by using colour overlay in layer fx or by placing a layer of solid colour over above your image and changing the bland mode to suit.
Background should be easy too once you have mastered your selection.
Make sure you move it onto a new layer, don't leave it on the background layer where it will not be transparent.
First thing on your list should be to go into 'Image > Adjustments > Curves' and adjust the curve similar to below, play with it.
You should see how more detail seems to equal more fuzz and there is no magical point at which you will have a perfect outcome.
You will have to decide at which point does the image best suit your purposes.
Once you have true black photoshop will have a much easier time cutting it out, you most likely still may suffer from black edges, which can be cured the same way i described above about changing colours.
If you have trouble and feel your stuck then i would suggest posting in the freebie section after you adjusted the curves to a point at which you are happy with the detail.
oh and Fractalius filter has great depth control and represents your image terrifically. (in a way that may be completely useless to you )
http://www.redfieldplugins.com/filterFractalius.htm
You have to pay for it, i would not suggest you do this to solve your problem however i felt like i had to mention it due to the image type.
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