Curves

Clive R. Haynes FRPS

Working with Luminosity
As mentioned earlier, in a brief 'Technical Aside', all the adjustments we tend to make using 'Curves' effect the colour and luminosity simultaneously.

When adjusting and modifying the shape of the curve we have been affecting the composite RGB content of the image. For small changes the alterations to colour, although present, are not significant. When the curves are made to undulate wildly then the excursions make dramatic changes to the colour as we observed on an earlier page ('psychedelic' imagery!)

Should we wish to target our changes to the underlying black & white (Luminosity) content of the image then we need to carry out the adjustments to 'Curves' via an 'Adjustment Layer'.
In the description to this point, it hasn't mattered whether the changes we have been making have been carried out via Image > Adjust > Curves or by creating an 'Adjustment Layer' for Curves.

I personally recommend the Adjustment Layer' route as the preferred option. To discover more about the advantages of working in 'Luminosity Blend Mode' and 'Adjustment Layers' see the 'links' at the base of this page.

Creating a 'Curves' Adjustment Layer.
At the base of the Layers palette, click on the half black / half white circle icon
From the 'drop-down' list that appears, choose 'Curves'.

The new Adjustment Layer will appear.
Click on the drop-down arrow to the right of the 'Normal' box (at the top lh of the Layers Palette) and from the Drop-Down menu, choose 'Luminosity'.