An interesting workshop on Photoshop swatches, spot colours and duotone - features which I have never used before. The use of isolating channels for screen printing and adding channels for spot colours was particularly useful and something which I will look at in more depth as part of the current print module.
Colour modes
RGB: Max = 255 and Min = 0
The default colour mode of Photoshop is RGB but can be converted through Image > Mode
By using CMYK, a lot of filters are unavailable suggesting RGB is the preferred colour mode
The following shows the colour difference between CMYK and RGB. The first, R = 0, G = 255, B = 0 results in a bright, fluorescent green but changes when converted to CMYK. This particular RGB colour is therefore outside the CMYK gamut.
Gamut Warning
The Gamut Warning tool allows you to see what colour are out of the CMYK gamut range. Before converting an RGB image to CMYK, it is useful to use various image adjustments beforehand to achieve similar colours.
Hue & Saturation
Simply decreasing the saturation through the Hue & Saturation tool allows you to achieve a similar outcome to CMYK conversion but with more customisation.
Replace Colour
'Replace colour' is another useful tool as it allows you to change the hue, saturation and lightness of a selected colour from the image. Fuzziness is the range of pixels that are included within the selection - similar to the tolerance of the Magic Wand tool.
Swatches
Alt + click removes swatches
You can add swatches in the 'Colour Picker' window
When choosing colours, the colour picker provides a warning as to whether or not it is in the CMYK gamut. The triangular warning sign alongside the 'new' colour swatch shows that this particular colour is not print ready. By clicking this icon, Photoshop chooses the nearest colour.
Spot colours
- Cheaper but with a limited colour (tonal) range
- Used in corporate branding to keep a consistent identity
- In the 'Colour Picker' window, you are able to access the 'Colour Libraries'
- A spot colour can then be added to the swatches palette
(Useful not only for inks but for varnishes etc also)
Monotone & Duotone
- You are able to add spot colours to greyscale images by going to Image > Mode > Duotone.
- Monotone = 1 spot colour and Duotone = 2 spot colours.
Duotone Curve
You are able to customise how the black will be replaced by a spot colour in the Duotone Curve window by altering the percentages or customising the curve itself.
Channels
- Photoshop defines the colours in an image through 'Channels'.
- Each of these channels consist of a grey scale image which defines the amount of that particular colour in an image
- Working with the greyscale image, you are able to add a 'new spot channel' to a specific selection of your image - a spot colour can then be chosen from the colour library (this can be changed at a later date however).
By hiding the greyscale channel, you are able to see where the spot colour will be printed. Painting tools apply when using the spot channels (much like layer masks).
