By Photoshopman a.k.a. Gary Small
When Photoshop CS4 was released, it was chock full of so many new features, it was hard to say which one was my favorite. As cool as most of them are, this one, in my opinion, arose out of necessity.
As a professional photographer who was raised on medium format, I got used to shooting square. Because of that, I was able to frame subjects in my viewfinder so I knew I would get a perfect 8×10 every time. Then along comes digital and I, along with many of my fellow pros, gave up our Hasselblads and Bronicas and went to 35mm DSLRs. The big downside to that is, it’s a very long, narrow rectangular format. I’ve found, more often than not, that many photographers would inadvertently fill the frame with the subject, only to find when they went to make an 8×10, they would have to either cut their subject’s feet off or do some serious Photoshopping in order to make it work into the 8×10 crop.
I’ve personally had instances where I had to take my Rectangular Marquee tool and select pieces of the image, in order to stretch the background to make the image fit the crop properly.
Then along comes Photoshop CS4 and a new feature, called “Content Aware Scaling” (CAS for short). This to me was a godsend. In a nutshell, CAS is a way of stretching or squeezing an image into a cropped format, without distorting the main subject of the picture. It’s very cool to see it in action, but takes a little understanding to get it to work properly.
The way it works, is it tries to identify what the main subject in an image is (for example, pictures of people would have a lot of flesh tone and in most cases, be at or near the center of the image.). After it does that, you would scale the image, much the way you would when you use Free Transform except that in this case, the part that was identified as the main subject is protected and Photoshop will stretch or squeeze the remaining pixels to scale the image the way you want it.
Sounds easy, right? Well, Photoshop doesn’t always get it right and as with most things, I’ve found that leaving any kind of adjustments on automatic usually yield less than stellar results. I’ve found that CAS needs a little help most of the time. We help it along by outright telling it what we want recognized as the main subject. [Screenshots showing the entire process step by step are at the end of this article —Editor] How? Well first, we bring up CAS by going to the Edit menu and choosing “Content Aware Scale” When you do this, you get a set of handles around the image that look identical to what you see when you use Free Transform. But, don’t do anything yet! Look all the way up towards the top of the work area at the Options Bar. Over to the right, there’s a little drop down box labeled Protect. This is where we can tell it what we want as our protected subject area. Now, hit the Esc key to get out of CAS for now, because we have some work to do first. Sorry, didn’t mean to be a tease!
CAS uses Alpha Channels to identify that protected area. So in order to do this, as you may have guessed, you have to first create an Alpha Channel. How do you do that? Well, for anyone who hasn’t taken one of my Photoshop classes, an Alpha Channel (which resides in the Channels Panel) is basically a saved selection. What I usually do, is take my Lasso tool, and draw a selection around the main subject of my image. I then go to the Channels Panel. That’s where you see the RGB composite and Red, Green and Blue channels that make up the image. Look all the way to the bottom of the panel and you’ll see some buttons. Click the second button from the left. This takes the selection and saves it as an Alpha Channel. The first one is appropriately named, Alpha 1, and so on. You’ll notice the thumbnail is a black/white picture of the shape of the selection you had previously made.
Now, go back to your image, deselect the selection you made, and click Edit>Content Aware Scale. Again, you’ll get the transform handles and the Option bar. NOW click the dropdown box labeled Protect, and you’ll see 2 choices: None and Alpha 1. Click Alpha 1 and you’ve chosen that selection you made to be the protected subject area. Now grab the adjustment handles and stretch or squeeze the image as needed. You’ll notice everything EXCEPT the area you originally selected transforms, or distorts. It’s very cool to watch and saves a lot of time and work.
One word of warning, if you don’t have much image area to work with, outside your protected subject area, Photoshop may have no choice but to distort some of the protected area anyway, or badly distort the remaining area and you could have unpleasant results. My best advice in situations like that is, when you shoot your images, shoot loose. Leave room for cropping or proper adjusting, and you will save valuable post-production time.
Step by Step Screenshots showing the process: