We often tend to have a problem finding 'neutral' area to meter when in the field. This
may also happen when you are using 'Light-Room' (I prefer to call digital dark-room as lightroom).
There are many ways to find a neutral tone or mid-tone in an image. This is an excellent tool
in removing color casts. I will write in details later on with all the screen shot but the following
write-up should help you. If you have any questions do not hesitate to contact me.
- Click the Create New Layer button at the bottom of the Layers palette to
create a new blank layer above the Background layer. Rename it to 'Grey to delete' as we will not need it
later on.
- Go to the Edit menu at the top of the screen and select Fill, which brings up the Fill dialog box.
The Fill dialog box has to drop down menu items - "Contents" and "Blending". Click on Contents and select the option
50% Gray from the drop-down menu that appears.
- Change the mode of this layer to 'Difference'. Do not worry if the image looks dramatically different.
- Create another new layer 'threshold' above this one (rename it threshold to delete), this will turn your image temporarily white.
- Now slowly begin to drag the triangle to the right until you begin to see black areas appearing in your image.
The first black areas that appear are the neutral gray areas you're looking for.
- Grab the Color Sampler tool from Photoshop's Toolbar (it's grouped in with the Eye Dropper tool),
click on an black area in the image to add a marker. You can now delete these two layers as we do not need them.
- Now create new layer - Levels or Curves. All we need to do now is click with the grey eye dropper (the middle one)
on the neutral gray marker we set in the image and Photoshop will remove the color cast from the midtones. You can
also perform this task using tools like Paint shop pro and gimp.
An example of the color correction. Move your mouse to see the effect.
Please note: In addition to color correction these images also needed some tonal correction.
It is often a case with digitized images, particulalry the scanned ones. Images scanned with un-calibrated
scanner often tend to have blue or magenta casts depending on the company. Article is a rough edit, may need corrections.
I will also add a tutorial about general photoshop corrections and importance of calibration soon. So check back again.
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