Tuesday 4 October 2011

Workshop with Mike: Photoshop

300dpi is the cut off point for commercial printing.  Anything higher would not be noticeable in the printed image.

Photoshop much prefers to work RGB, rather than CMYK.  This could be a problem when working with filters, when a selection of filters available in RGB are not available when the same image is converted to CMYK.

To demonstrate the differences between the two colour modes, a document was set up in RGB.  A selection of the canvas was coloured in R=0, G=255, B=0 (pure green).  When converted into a CMYK file the colour was changed dramatically.



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Working RGB and Printing CMYK

A sample image of a lake in RGB was used in this experiment.  When working with a photographed image it is important to get the colours right for print.  A way to see if the colours in RGB will be printed correctly is to use the 'Gamut Warning'.  This brings up any unprintable areas in grey.  It can be adjusted manually by adjusting the saturation, or certain colours can be picked out for adjustment in the 'Replace Colour' tool.

Another option is to proof the colours, which will temporarily shift it to CMYK.  This gives a preview before the shift of colour modes.

View > Gamut Warning ⇧⌘Y
Image > Adjustments > Replace Colour
View > Proof Colours ⇧Y




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Photoshop Swatches

In Photoshop, the swatches work a little differently.  The only method of deleting swatches is to hover over them and to alt + click them.  Creating a swatch from pantone is a problem as it doesn't save the reference number.

When working with monotone or duotone, however, the pantone reference is saved.  Below is an example of how I applied this to the image, adjusting the levels of colour.  Another way to add spot colours to photographs is to include it in the channels.  By making a selection, it is possible to highlight certain areas of the document in a spot colour, demonstrated by the highlighted boat below.





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