Photoshop / Channel Paths

October 28, 2013 § Leave a comment

In this session with Steve we began looking at the use of channel paths within Photoshop and their practical uses with the layering of multiple images. Channel paths are used as (another) way to remove subjects in images from their background but in a more detailed fashion, we performed this task on a portrait photograph of a model who’s hair was wind blown, so the objective was to separate the model and as much of her hair strands away from the background as possible and pasting it on to another document.

Like most of the methods we’ve been shown, this is a non destructive way of editing documents, which can’t be stressed enough, I’ve been in the situation where I’ve performed ‘destructive’ editing and had to live with the consequences, which is not fun, so I do my utmost to keep my techniques to a non destructive level.

Channel Pathsmodel

1. On the right side of Photoshop where you find the layers tab you can click on the channels tab, here you can turn the RGB channels on and off.

2. Next I needed to find which layer contained the most contrast, to do this look for the layer with most contrasting black & white in it,cycle through each colour by turning off all the RGB layers and viewing one colour at a time. Duplicate this contrast layer, this will be used to create a mask.

3. To adjust the layer’s levels go to ‘Image’ > ‘Adjustments’ > ‘Levels’.

4. This levels graph present us with the tones that are on the image, darker tones (like shadows) on the left, mid tone greys in the centre, and highlights and whites on the right. At this point I adjust the whites to 224, and the blacks to 36, and moving the white output levels slightly

5. Here I use the paintbrush tool (with 100 hardness) to cover the majority of the figure, leaving an outline around her as this will be editing in the next step with some additional tuning.

6. To paint the edges and the loose hair I need to increase the contrast (or be able to see the little bits of hair) to do this I use the paintbrush but changing the mode from normal to overlay and dropping the opacity down to 30%-40% this allows for a softer brush style which doesn’t affect the white background. When painting you can also highlight the patches with white that are too black i.e. the hair where you can see through, press ‘x’ to flip between black and white.

7. The next step is to select the mask we just created, to do this you press ‘CMND/CTRL’ and then the mask, then inverse it > create a mask > turn all the channels back on > with the mask selected, invert the selection again > click any selection tool like the marquee > click ‘refine edge’ bringing up the window you see in the image.

8. By switching the view mode to black you’ll be able to see a halo effect, to rid of the halo like effect the model currently dons I want to change the percentage of ‘Shift edge’ to alter the amount white/black.

9. Switch between the white and black view modes to see what the image looks like and get the balance right.

10. To reduce the hardness of the edges I apply 1 pixel (no more than 2) to feathering, softening the edges.

11. Next I change the output to ‘New Layer Mask’ which copies the edited photo onto a new layer.

12. Apply the new background image.

13. To finish I soften the glowing edges on the hair by using a softer paintbrush and reducing the opacity, while the mask layer is selected.

The below gallery shows the progress, with annotations of the above description on each.


Additional notes:

– Dropping images into Photoshop converts them to smart objects, where as dropping them onto the the Photoshop Icon/logo opens it in a new tab.

– When photographing subjects and you know you want them on a black background then do that instead of this process, save’s time.

– Ticking the ‘Decontaminate colours’ box in ‘Output’ in the ‘Refine Edge’ settings will remove non neutral colours like blue and green, if you were to use a green/blue screen.

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