"Ink Outlines"

How It Works
STEP 1
Set to Stroke Length 7, Dark Intensity 5, Light Intensity 5, a fine line (always black, irrespective of palette settings) traces color and tone edges. Mottled patterns can be seen in the balance of the image and, in close-up, some vestigial cross-hatching can be seen in the highlight areas.

STEP 2
The Stroke Length control is curiously named. Setting it to maximum (50) has the effect of spreading highlights and displacing the traced line — compare this close-up with the previous example.

STEP 3
A useful compromise setting (15, 5, and 50) gives a more effective result that's lighter and not so emphatically mottled.

STEP 4
The same settings applied to the target image show the line displacement. Note the metallic effect that has appeared over the area of gray gradation.

Using The Ink Outlines Filter
You can use Ink Outlines as a remedy to breathe some life into otherwise flat subjects.

STEPS 1 & 2
Duplicate the original image in the Layers palette and apply the Ink Outlines filter. Keep the Stroke Length low to avoid overpowering the original image. Here, the values that we have used are Stroke Length 2, Dark Intensity 11, and Light Intensity 30.

STEPS 3, 4 & 5
Even at a low setting such as this, the effect is too strong. Use Edit > Fade > Ink Outlines to restrain it.

STEP 6
In close-up, it's easy to see the reviving effect of the filter.

Fixing Color Cast With Ink Outlines
Another rescue mission involves mitigating irreversible color casts.

STEP 1
A heavy cast due to fluorescent lighting, with no corrective filtration at the moment of shooting, can still be sidestepped.

STEP 2
Select the whole of the image (Ctrl/Cmd+A) and copy it (Ctrl/Cmd+C). Open the Channels palette, make a new channel, and paste (Ctrl/Cmd+V) the image into it. The channel window will now show the pasted image in monochrome.

STEP 3
Use the Ink Outlines filter at low values: Stroke Length 2, Dark Intensity 14, and Light Intensity 26.

STEP 4
Hold down the Ctrl/Cmd key and click in the alpha channel thumbnail. Return to the Layers palette where the original image will show the alpha channel selection. Hide the selection (Ctrl/Cmd+H) so that the work area is easier to see.

STEPS 5a & 5b
Use Image > Adjustments > Brightness/Contrast to lighten, and reduce the color strength of, the selected areas.

STEPS 6a & 6b
Though the correction is acceptable, more detailed work can pay dividends. The originally bright yellow warning panels and handrails are now pink. Click the Eyedropper tool in a typical pink area and go to Select > Color Range. Select the central eyedropper icon to add more related colors to the selection by clicking in the main image window. Choose White Matte as the Selection Preview from time to time to check progress. When satisfied, click OK.

STEPS 7a & 7b
Use Image Adjustments > Color Balance (Ctrl/Cmd+B), uncheck Preserve Luminosity and increase the yellow component in Highlight, Midtone and Shadow areas. When you're done, click OK and then Ctrl/Cmd+D to deselect. The handrails and warning panels are now much closer in color to the original.