Inghard Ehrenberg

Post-Processing II – Colour Spaces

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Take a BowColour Spaces

Most cameras are set by default to use a certain ‘colour space’, within which to capture images. That colour space is termed ‘sRGB’ – standard Red, Green & Blue.

Bear with me for a moment while this is explained.

Imagine this: You’re a painter, and you’ve been commissioned to paint an accurate colour picture of Australia. There are some conditions though – your painting must depict all of Australia as it looks just after dawn in ByronBay, on a sunny day. And there’s one more condition: Your painting must fit onto a postcard, and be visible in detail, unaided, to the naked eye. Of course, the Western part of the continent would still be pitch black, when on the Eastern seaboard there is brilliant sunshine with reflections from the sea…

How will you do justice to it? Fortunately, your persuasive skills come to the fore, and you convince your patron to agree to the painting being done on a sheet of A2 sized canvas. Phew!

Hopefully you can appreciate the problem – how on earth would all of the colours needed to portray Oz fit onto a postcard? The space just ain’t there!

Conceptually, that’s all a colour space is. It’s a map of a surface (it can be depicted as 2D or a 3D object), and that surface must depict all useable colours and every possible shade combination in between. It stands to reason that the larger the colour space, the better it can depict the subtle differences between shades of colour (even shades of grey if it’s monochrome).

A larger colour space is known as a wider ‘colour gamut’.  While sRGB is a popular colour space, its gamut is not all that wide. It’s used in part because it approximated the colour gamut of a computer monitor (the old CRT style at the time).

Importantly, there is an alternative to the sRGB colour space – the most popular (and available) being Adobe RGB. It is a larger colour space (thus having a wider gamut) than sRGB, although most monitors cannot display its entire palette of colours.  That capability is changing – flat panel monitors which can use nearly all of the Adobe RGB colour space are becoming affordable.

If all you want to do is display images on the web, sRGB is fine – you’ll lose nothing. However, Adobe RGB has a trick up its sleeve – it closely represents those colours of which good inkjet printers are capable. If you are intending to print images, select Adobe RGB as the colour space in your camera for that reason. Most (at least in the DSLRS) will have this setting as an alternative to sRGB, and you are then capturing the best possible image for later printing. Whether you can appreciate Adobe RGB’s full capabilities on your monitor is less important than feeding your printer the best possible data with which to make your final print. To make life easier for editing in Adobe products, that software ensures that the benefits of the wider colour gamut are preserved during editing, and realised at the business end.

Printers and printing combined is another element to this chain. That will be left for a later section, as it deserves some in-depth treatment in its own right.

Lastly, notebook screens. Notebooks are good for clearing your memory cards, or as a backup device.  Don’t try and edit images on them using the notebook screen. If you don’t believe me, or need some entertainment, try to calibrate and profile one…  Hook it up to a desktop monitor, or transfer the image to the desktop for editing.

 

Next – Post-Processing III: Image File Formats – They Matter

 

History

30 June – edits, links added

One Response to Post-Processing II – Colour Spaces

  1. Donna June 30, 2015 at 4:25 am

    excellent info