PWP is Picture Window Pro, a sophisticated image editing tool available from Digital light and Color: www.dl-c.com. To the best of my knowledge it’s not possible to carry out these manipulations in any other image editing package.
Pretty much any version of PWP can be used, from 3.1 through 4.x and it is excellent for the task, displaying changes instantly on screen and allowing fine intuitive control of the manipulations being carried out.
I assume that you have a good working knowledge of PWP, however some discussion of the transforms that we will use follows for those not too familiar with them and their trickier features.
The color curves and grey brightness curves are the main transforms used in this article. These transforms are similar to each other with a similar user interface, the colour curves transform has extra features to enable you to work on individual channels in RGB, HSV or HSL mode. Grey brightness curve has some limited functionality here when you work with a colour image.
The probe within these transforms defaults to off. Always switch it on as you will be using it a lot.
Be aware that switching between the modes of the colour curves transform (e.g. HSV to RGB) loses any previous settings, so if you have something interesting, save the values before switching.
These transforms default to a curve view. I prefer to use the histogram view and all the examples are worked around that view. The histograms are double histograms, showing the input image histogram on top and the output image histogram underneath. To aid interpretation, the histogram view also includes a curve representation, this will help those more used to working in the curves view.
The histogram transforms use double headed arrows to map tone points from source (input) image to output image. I refer to these as control arrows. They correspond exactly to the control points in the curves view and if you wish you can swap between the curves view and histogram view using the appropriate icons.
Add control arrows to the colour curves and grey brightness curve transforms by positioning the mouse either over a tone in the image that you wish to create a control arrow for – or at the appropriate point in the double histogram view, then shift left click.
Remove control arrows from these transforms by moving the mouse over the unwanted control arrowhead, either at the top or bottom until the mouse pointer changes to indicate that the control arrow has been selected, then ctrl click.
Note that control arrows cannot slide past each other in the top (input) line of the histogram, but can in the bottom output line.
Histogram expansion defaults to low, this tends to hide many tone areas of the image that we are interested in. Throughout this article I will assume that you always set the histogram expansion to high when you open the transformation.
Although scales are not always clear in the histogram transforms (the scale is fractional – halves, quarters etc.), I will use the convention of 0 to 100 to indicate slider & pointer positions on the histograms. 0 being fully left, 100 being fully right. This corresponds to general usage on the DL-C discussion forum especially within Den’s tutorials.
Resize the transform window as necessary to get the fine control you need.
Ensure that you have auto preview set on in the transforms
The curves can be saved. In the grey brightness curve there is no confusion, but in colour curves transform there are 2 places to save the curves, saving different curves in the place. Always use the one at the top of the transform box.
Clicking on the options button should only cause the dropdown to open. However it is possible to click in such a way that reset is selected and applied. This loses your work and is most frustrating. I suggest that you make a point of always clicking and holding; then when the drop down opens, slide the mouse away from reset before releasing the pressure.
PWP does not link the curve save directory to image directory – it retains the last directory used for saving a curve. This can lead to ‘lost’ curves – so if you wish to save curves with the images they’re used on (my preference) instead of a general curves directory, make sure that you change the directory before saving.
Although I will not be discussing it in depth in this article, all the transforms discussed below can be applied through masks to restrict the effect to specific parts of the image, so increasing the power significantly.
You will find that the inversions sometimes bring out dirt, dust etc. in the image, even though you spotted it meticulously. After finishing the inversions, make time for a second clean up session.
As with most, if not all transforms, PWP’s amount slider(s) can be used to adjust the amount of the transform effect. Consider their use to obtain a more subtle effect.