Jacob's Ladder
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Jacob's Actions

I want to share with you a really clever new way of correcting images - it was discovered by Jacob Rus and is appropriately called Jacob's Ladder. When Jacob posted this technique, even the great Dan Margulis was speechless. It is so simple to do and yet extremely powerful on awkward images.

It is probably easier to experiment with this technique (I've included some Photoshop Actions you can download) rather than try and understand the nuts and bolts of it - but let me attempt to show you...

In this step wedge, I want to change one of the steps to yellow
so I need to increase the lightness of the wedge

and add some Yellow (in the b curve) 
- move up to add yellow and down to add blue.

Notice that we curve from a horizontal line!
and this is the result, 
rgb 255,255,0
Now to change another one to green - again it needs to be lighter than the original rgb 50,50,50

Notice that the points line up with the step wedge (if I'd scaled the images to be the same size).
add a touch of green (the a curve is moved up for magenta and down for green) 

and some yellow from the b curve.
All quite easy, apart from having to add extra points to the curve to keep the line horizontal.

Well, that is hardly impressive, but hopefully you get the idea.  Adjusting colour is simply a matter of making a colour warmer (magenta or yellow) or cooler (green or blue) - independently of it's brightness -  wait until you try it on real image.

There is a wee annoyance (using Photoshop's curves dialog) and that is having to add extra points where you do not want any change, and also the Info Palette doesn't work (one of Photoshop's bug/features!) - but using a Colour Watcher gets you around that problem.

This strange image of Wells cathedral fooled the camera with sodium lighting and daylight.

Actually this image is extremely hard to correct using normal techniques - people tried on the CurveMeister course, making multiple passes in various colour spaces and the results were pretty bad at balancing the colours.
  
Here is the final image and below the curves to do it - simple and incredible isn't it?

If this exciting new idea interests you, then read on...