HSV Colour Space Adjustments
HSV splits the image into 3 channels –H, S
and V. Each is independent of each other – so can be adjusted in isolation
without fear of changing something else that you are happy with. In contrast,
if you change want to change brightness in RGB, all 3 channels must be
adjusted. Just changing one channel in RGB causes the overall image colour to
- H controls the hue or colour of the
image. The transform shows the actual colours in the histograms, as well
as in the curve display. It’s possibly easier to conceive of it as a
colour wheel starting and ending at red, with the values of H representing
how far around the wheel you have travelled. PWP does not allow us to
easily cross this red/red boundary. As the value of H increases, the
colour shifts from red, through yellow, green blue magenta until red is reached
again. In doing so it is possible to select any individual colour in the
- S controls the saturation or the amount
of colour. Higher values of S introduce more colour into the image.
- V controls the brightness or lightness of
the image. Higher values represent more brightness. It is exactly the same
as the brightness channel that we have used for the monochrome
My general order for adjusting these is V,
S and then H. Fine tune as necessary afterwards. Apply the changes cumulatively
– not in isolation. As you will see in the workflow suggestions, I recommend
saving any interesting possibilities that you create, then later carry out some
fine tuning. If you find the colours obtrusive whilst adjusting V, temporarily
reduce S (saturation) to 0 while you adjust V.
You will find that having worked through
the monochrome manipulations that the V and S channels are simple and
straightforward. However the H (colour) channel can b a little less clear,
partly because of the high number of possibilities and partly because all the
effects in it are dependant on the previous two adjustments.
- Keep the original image open (not
minimised) and use the medicine dropper to sample areas that you are
interested in. Move it around to establish the colour range.
- If you are not sure where a particular
colour is mapping to in the output (a frequent issue), sample the colour
from the original image to see where the red line is, then shift click on
it and see where the bottom point of the new control arrow resides. Delete
the new control arrow if you do not need it.
- Radical adjustments in the control arrows
will cause other effects in the image. Check the curve that PWP
superimposes on the double histogram. If necessary add anchors to keep the
curve where you want it.
- When carrying out operations on a limited
range of colours, add an anchor on each side of the control arrows that
you are using to do the adjustment. In need add more further out. Add
these control arrows before making the adjustment, so as to minimise the
problems with lost/hidden arrow heads
- Expand the transform window to the width
of your screen to make it easier to distinguish between the control arrows
in the transform.
- Many effects and results are possible on
a single image. Experiment, save the curve, experiment some more. Take
promising ones further at a later stage. If you suddenly get an idea, save
the curve for later experimentation (with a descriptive name) and try the
idea out. I find that following ideas stimulates further ideas.
- Follow the suggested workflow given
below. In the examples that follow I will follow the same workflow, but
will skip steps that are already covered in the monochrome section, unless
there is a new point to make.