[Gimp-user] Picking Gray Point in a Photograph and recalling pixel points

[DJ]

Hi laptop, gimpuser,

>> Why would you want to use a sample point for the gray point in the
>> Levels tool? Just click on the "Pick gray point" eyedropper in the
>> Levels tools and then click on the spot in the image that you want to
>> select as the gray point. This will do what Norman described, just
>> completely automatically. You may want to adjust the Sample options in
>> the Levels tool options though. Choosing a larger sample radius often
>> helps to get better results.

> I think the difficulty is how to decide where the mid-grey point is.
> Once decided upon then action is easy.

I thought the tutorial might have had the answer to that by using the
50% gray layer with Mode: Difference.
http://digital-photography-school.com/precise-color-cast-correction-with-gray-fill-layers

snippet:
 "This simple tutorial solves this problem by finding neutral gray in
 the image, thereby removing the need to guess the color. In order for
 this trick to work however, your image MUST contain 50% gray tone
 somewhere in the image; otherwise the color correction will be off.
 ...
 The ‘Difference’ mode is a comparative layer mode that will invert
 pixels containing 50% gray, turning those pixels black."

I know there are many ways to achieve the end result, but part of
these tutorials is about learning and experimenting, so the knowledge
can be passed on. :-)

Thank you.

-- 
__________________________     
DJ