By Stephen Farnow
1. DON’T SLACK, MAKE SURE YOU BACK (YOUR FILE)
Your pixels never did anything to hurt you, did they? You, on the other hand, are likely roughing them up every time you enhance an image. Directly adjusting color, contrast, or focus, all staples of image digital enhancement, physically alters your original data (i.e. munches your pixels). Now you may not really care all that much about your pixels but you will when you realize you’d like a “do over” and they shrug and say “so sorry.” Fortunately, Photoshop has a whole host of techniques that fall under the category of nondestructive editing or NDE. They allow you to make all the changes you want without ever touching your original data, and you can go back and do touch ups later.
The simplest start, of course, is to make a backup of your file before the pixel plundering process begins. This is highly recommended, irrespective of whether you follow the remaining suggestions in this article or not. Next, always duplicate your background layer by dragging it onto the New Layer icon at the bottom of the Layers panel before doing anything else. By preserving that background layer, your Photoshop file will always contain the original pixels.
2. LOVE LAYERS FOR ADJUSTMENT
Photoshop’s image enhancing commands can be found under Image>Adjustments from the main menu bar. There are adjustments to fix contrast, color, exposure, convert to black and white, etc. This last adjustment, Black & White, is a great example of a problem with these adjustments. When you select the Black & White adjustment, Photoshop, with some settings from you, converts your image to black and white, throwing away all of the color information. Not only is the color information gone, the conversion settings are also history. (example image available)
There is a better way. Just above your Layers panel, and new to CS4, is the Adjustments panel. If you don’t see it, select Window>Adjustments from the menu bar. Most of the adjustments listed under Image>Adjustments are available here. But the difference is that these are adjustment layers, not commands. When you select one, it shows up as a new layer in the Layers panel and its settings become available in the Adjustments panel. (Adjustment layers are also available in earlier versions of Photoshop. Click on the half-filled circle icon at the bottom of the Layers panel.) (example image available)
Rather than actually adjusting pixels, an adjustment layer stores the adjustment instructions, pixel by pixel. The image displayed by Photoshop is as if the adjustment was performed. In fact you can turn off visibility on the adjustment layer (by clicking on the eye icon) and the adjustment will disappear. Furthermore, if at some later time you wish to modify the settings for the adjustment layer, you can select that layer (assuming visibility is back on) and all of your original settings come back, available for tweaking. This is the essence of NDE. The original pixels are untouched and the original settings are always available.
3. MAKE MASKS FOR LOCAL CHANGES
When you create an adjustment layer, the result is global, meaning that all pixels in your image are affected. What about when you want to localize the effect to a specific object in your image? The old you might have done a selection around that object and then modified it with the Image>Adjustment commands. Not only are the pixels changed and the adjustment settings unavailable, that selection can’t be altered later either.
The new you should consider selecting that object and then creating the adjustment layer. When you do, the layer mask that automatically comes with the adjustment layer (the little thumbnail to the right of the adjustment icon) will reflect your selection, restricting the effect of the adjustment to your original selection. Where the layer mask is white, the adjustment shows through; where it is black, the adjustment is blocked. (example image available)
The beauty of this approach is that the mask (your original selection) can be altered later if necessary. You can use a white or black brush to touch up locations where your original selection might have been off.
4. MORE MASKING MANIA
The power of layer masking doesn’t end with adjustment layers; you can use it on ordinary layers as well. Imagine compositing the Eiffel Tower onto a hillside in New Zealand. You might have duplicated your Eiffel Tower image over the New Zealand background and then used some extraction technique (the eraser, a selection tool, etc.) to delete (i.e throw away) all but the tower itself. The better NDE way is to import the Eiffel Tower image, create a selection around it, and then click on the Add Layer Mask icon at the bottom of the Layers panel. A mask is added to the tower layer, hiding all but the selected regions of that layer. In this way, you can touch up the Eiffel Tower selection at any time by editing the layer mask. (example image available)
5. SMART OBJECTS REALLY ARE...SMART
All of this is great for adjustments. But what about transformations? Scaling the contents of a layer forces Photoshop to redistribute that layer over a fewer or greater number of pixels. If you scale an object down by two in each direction, for example, the scaled object will lose 75% of its pixels. Those lost pixels are gone. Forever!
The NDE solution for this is Smart Objects. Prior to transforming an object, simply convert its layer into a Smart Object layer. Select the layer and in the main menu, choose, Layer>Smart Objects>Convert to Smart Object. Photoshop will then create a snapshot of the layer and will invisibly store it within your file. The only indication that something has changed is that the layer icon changes to a smart object layer icon. Now if you transform, Photoshop displays the effect of your transformation but leaves the original pixels, the Smart Object, alone. You can scale down with no loss of pixels. You can even still edit the Smart Object layer by double clicking on it. Now that’s nondestructive. (example image available)
Photoshop is lots of fun and can be very, very rewarding. Doing things over in Photoshop because you messed it up the first time is not nearly as much fun and is certainly far from rewarding. By using the nondestructive editing techniques described in this article, you’ll always have your original pixels to manipulate and all of your edits and adjustments to tweak. Most importantly, you’ll be able to avoid the dreaded do-over flow.
Stephen Farnow, author of
Photoshop-Just the Skinny, spent 30 years in management at high-tech companies such as Texas Instruments and Intel. He is currently a management consultant and also writes about graphic arts. For more information, visit www.JustTheSkinny.com/photoshop.html