Starlight Xpress SXV-M7C - Manual (Page 8)

Handbook for SXV-M7C Issue 1 June 2004
8
After a few seconds a recognisable colour image should be displayed, although the
colour ‘balance’ may need correction. This is especially true if your image was taken
indoors with artificial lighting, which can make everything look very orange.
If the colour image shows white spots or patches, where no colour is present, then the
original exposure time was too long and some pixels are overloaded. In this case, you
need to take a new image with significantly less exposure time, or with the lens
stopped down a little further.
Correcting and refining the colour image:
The colour balance of your image may be adjusted by selecting ‘Colour’, followed by
‘Set Colour Balance’.
You are presented with three histograms, which represent the Red, Green and Blue
content of your image, with limits, which can be adjusted by slider controls.
A good quality colour image will present three, roughly similar; histograms, and any
small colour bias may be seen as different offsets above zero and different widths of
the main bulk of the histograms. Moving the lower limit setting of a histogram will
adjust the overall colour bias of the picture, with the amount of the particular colour
concerned being reduced by moving the limit in the positive (to the right) direction.
The location of the pointer represents the new ‘zero’ of the histogram. For instance, if
your image is a little too red, you can reduce this by setting the lower pointer on the
red histogram to, say, 4, and then clicking on OK. Equally, you can increase the red
content by reducing both the blue and green content.
In some cases, there may be a difference in colour bias between the faintest and
brightest objects. When this happens, first reduce the error of the faint detail, using
the ‘START’ sliders, and then correct the bright objects by using the ‘MAX’ sliders.
The ‘MAX’ slider allows you to vary the ‘slope’ of the transfer curve and so change
the way that the balance alters from faint to bright detail.