Digital Infrared Capture & Workflow continued

Clive R. Haynes FRPS

Adventures with Lab Color Mode
If you've arrived at this page from the 'Know-How' contents list via the 'Lab Color Mode' 'link', you may wish to return to the beginning of the section about DI IR Capture & Workflow, if so, you'll find a 'link' at the base of this page.

As mentioned, the ability to separate the 'L', 'a' and 'b' channels can offer certain advantages and these allow further excursions and adventures. To give an indication of the variables that one can enjoy, I'm going to use my image of 'The Skiff & The Hulk' picture as an example. Please remember that not all tonal changes will affect all images equally and that the results obtained are, understandably, referred to 'false colour', therefore the tones and colours cannot be wrong - only more or less pleasing or appropriate. Within these 'pages', I can do no more than 'raise the lid' of this particular 'virtual box', courtesy of a digital Pandora.

The example images were taken on an IR converted Nikon D70, using an in-camera Custom White Balance (very important, see previous pages), opened as a RAW file via Adobe Bridge and managed in Adobe Photoshop CS3.

To help with clarity and workflow, I've included screen-grabs which illustrate Histogram, Channels and Layers. There's not a 'follow this route to success workflow' for exploring the tonal opportunities in 'Lab', however, the following series of worked examples will help both to point the way and to provide an introduction.

Please remember that the results will be image dependent and the examples illustrated here may not replicate with your chosen image.

(Note: 'quick key' / 'short-cut' references in brackets, apply to a PC - my apologies to Mac users but I'm more familiar with a PC)

The starting point is the image shown below.

Above: Original RAW file
Above: Opening Image screen-grab showing Histogram, Channels and Layers
After opening the image, convert to 'Lab Color' (Image > Mode > Lab Color) see below


Make sure that you can see the Channels palette,as below. If it's not visible, go to Windows > Channels.

Channels Palette

Beginning to explore the flexibility of 'Lab mode', experiment by Inverting (making negative) each channel. This simple exercise will illustrate the independence of each channel or combined Channels, that is to say 'L', 'a', 'b', or combinations 'L'/'a', 'L'/'b' 'a'/'b', 'L'/'a'/'b'. As you can see, we have seven independent options at our disposal. To understand the principle we'll look at just two, the difference between 'b' alone and the combination of 'b' / 'L':

Click/highlight Channel 'b' (quick-key = Ctrl + 3)

Make certain that the eye icons for each of Channel is 'on' (but only 'b' Channel is highlighted / active)

'b' Channel Active
Next: Go to Image > Adjustments > Invert (Ctrl + I) and the image will be subtly different, (see below), to our original, as only b (blue content) has been inverted.
Above: Screen-grab showing 'b' Channel 'Inverted'


To continue this exploration
Next: Undo the change above, Edit > Undo Invert (Ctrl + Z) to restore the image to the starting point.
To continue, please click on the link below


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