In an era when working on 30 megapixel and higher images has become the norm, a Photoshop document with dozens of layers can quickly become a burden to work with often slowing to a painful delay after each stroke of a brush. The simplest solution is to constantly be crushing those layers down into a single flat layer but this method is the antithesis of non-destructive editing which can make future client feedback rather difficult to implement. Instead, lets focus on few easy tricks you can do to keep your computer running smoothly during the most complex of composites.
1. Turn Off Your Adjustment Layer While Working Below Them
The logical method of editing is to place your color grading and toning at the very top of your document within a series of adjustment layers. It is also quite common for photographers to create these layers at the very beginning of a retouch to give themselves a "feel" for how the image will look once complete. Most photographers will then begin their retouch or compositing work below the adjustment layers so they can see the full impact of each change as it is made. The downside of this, unfortunately, is that after every tiny change Photoshop must re-render the preview along with all the adjustment layers often numerous of times per second. Each additional adjustment layer adds additional work for Photoshop and slows down your computer. Instead, hide all those adjustment layers while you are working. You don't need to be looking at a perfectly color corrected photo while you are cloning skin blemishes. The benefit is that Photoshop will run much faster.
2. Shrink Your Photo
The fact that your magnificent Canon 5DS can make 50 megapixels of data in a single exposure is certainly impressive, but do you always need that much resolution for every image? If you are planning to print large, certainly maintain as much data as possible, but if you are working on a shot destined to only display on the web or to never be printed larger than an 8x10 headshot you don't need 50 megapixels of resolution. Make the first step of your retouching process the act of asking yourself what the largest size you will ever need for a given photo and only editing at that resolution. It is amazing how much better Photoshop handles a 20 megapixel image compared to a 50 megapixel one. For those wondering, and as an example, an 8x10 headshot printed at 300dpi is less than 10 megapixels. Very few photographers ever truly make use of a high resolution sensor.
3. Create Stamp Visible Layers.
When working on a complex composite each element usually is on its own layer, frequently with its own set of color grading to match the tone of the scene. For every new object added to the stage Photoshop slows considerably. Rather than crushing all those layers down which obliterates editability, instead create a stamp visible layer above them then hide all those other layers. You can always remove the stamp visible layer later but while it is in place Photoshop doesn't need to re-render dozens of layers each time you make a small change. To create a stamp visible layer create a new, empty layer above all the layers you wish to be included, and hit command-option-shift-e (control-alt-shift-e on windows). You can then edit above that layer without forcing Photoshop to re-render anything below it on every change.
Photoshop continues to demand greater and greater resources of our computers. Rather than spending every dime on the fastest, most impressive computer money can buy, adapt your editing workflow slightly to help Photoshop stay quick, even if you aren't using the latest in super powered GPUs. This post really only skims the surface of a potentially limitless topic, I'd love to hear some of your favorite Photoshop accelerating tricks in the comments below.