Skycleaner

xero : skycleaner helps tackle one of the most common problems in photography - bleached-out skies caused by over-exposure. Unless you are a very serious photographer, with enough time and dedication to wait for just the right light at just the right time of day, you'll see this problem on a regular basis. It certainly seems to afflict about nine out of ten of my photographs!

	This picture was taken on a day with bright cloud-cover; the sky is almost completely burned out through over-exposure, and the resulting picture is less interesting as a result. We could put a layer with an interesting sky beneath this one, then perhaps manually erase the blank sky to let the new one show through, or perhaps use the layer transparency ranges... We could even use an 'eliminate white' filter. All of these approaches have their drawbacks, and leave us with a lot of manual touch-up work to make the result presentable. I, for one, don't have that much patience...
	Start by making a rectangular selection to cover the top half of the image. This should extend from the very top of the image, down to the horizon or thereabouts. The selection doesn't have to be rectangular, of course, but this is usually the simplest approach. Don't worry about including the trees - skycleaner's job is to leave them in-place! Hint: Stretch the window a little so that you can see the 'hatched' area beneath, and start your selection outside the image to be sure of not leaving any unselected areas. Use the shift key to add to the selection if necessary, or the control key to subtract from it.
	Now, create a new raster layer and place it beneath the main image - you may need to promote the main image to a layer if it is currently the background (right-click it in the layer palette and select 'Promote to layer'). Leave the selection marquee in place. On the layer palette, click the spectacles icon on the main image layer to make it invisible, then click the new lower layer to make it the active layer. Finally, use the fill tool to fill the selected area with a suitable gradient - here, I've used a gradient of pale blue (217,218,255) fading to pale yellow (255,255,192); the cut-over slider on the gradient box is set to give about two-thirds blue to one third yellow.
	Now, since the sky is reflected in the river, it would be nice if we could apply a suitable colouration there as well. No problem... invert the selection, then invert the gradient, and use the fill tool in the bottom half of the layer to give a mirror image of the top part. I've used the same colours here, but you may want to change them subtly to give a more realistic effect.
	Once you've dealt with the lower part, invert the selection again so that the top half of the image is selected, then make the upper layer active again, and click its spectacles icon (on the layer palette) to make it visible. Ok - time to put skycleaner to work! Remember that you can click on the thumbnails for a better view of what's going on.
	Now, start up xero:skycleaner by selecting Effects->Plugin filters->xero->skycleaner from PSP's menu. Slide the 'Threshold' control to the left until most of the sky becomes transparent - if you're lucky, the default setting of 50 may be just about right. Unfortunately, plugins can only see the active layer, so the transparency will appear as the familiar pale-grey checkerboard pattern in the preview window.
	Zoom the preview window in to 100%; you can either click repeatedly on the '+' button, or hold down the shift key and click once. At 100% zoom, click and drag on the preview window to find the edge of the trees. The edges will look slightly messy, but you can now improve matters by moving the 'Threshold' slider a little either way, and judging the effect in the preview window. Click on the little arrows at the ends of the slider to move by unit increments. Try adjusting the 'Strength' slider too - aim to remove the light fringes from around the darker details.
	Now you can adjust the 'Softening' slider to make the tree edges sharper or softer. Experimentation is the key here, and it can be a little hard to judge the end result without being able to see the layer below. In case you're wondering, the filter's softening function affects only the edges where the image becomes transparent, though you may see some softening of other details at the highest settings. When you're happy, click the 'Ok' button to see the final effect on the main image.
	Ok, but we still have those reflections in the river to deal with. No problem - we can make a rough-and-ready rectangular selection of the bottom-left corner, then use skycleaner again to let the lower layer show through. Note that we can't just select the whole of the bottom half of the image here - the woman's blouse is white, and would be made transparent too! Now, if I could only invent a filter that would really make women's blouses transparent... (In case you're curious, the lady in the picture is my wife, Kathryn, and the two boys are my sons Lee and Jack).
	All done! That's a big improvement, but you may want to experiment with using real skies from other photographs. Also, remember that even a bleached-out sky will sometimes have some texture in it; it can be worth changing the threshold setting to leave some of the texture in place - it usually ends up looking like thin cloud.