Scaling images way up—which is to say, enlarging them a lot—is never something you would choose to do, but sometimes you have no choice. A client’s picked their shot and they must have it in a poster, so that leaves you with the tricky job of blowing it up without it exploding into a pixelated mess. Most image editors do a good job with reduction or slight enlargement, but for huge increases in scale with maximum quality, you need dedicated software like Alien Skin’s Blow Up, now at version 3.
Installed as an Intel-only, 64-bit application, Blow Up can be used without having to rely on host programs such as Photoshop ( Macworld rated 4.5 out of 5 mice ), Lightroom ( Macworld rated 4.5 out of 5 mice ), or Photoshop Elements ( Macworld rated 4 out of 5 mice ), but its installed plug-ins can be used as an easy bridge from those programs as well.
With optional output size presets, sharpening, cropping, and unconstrained stretch options, Blow Up gives enough control that you’re not forced to use an external editor to finalize your upsampled images. One size definitely doesn’t fit all for enlarged images—you might want smooth and sharpen graphics or add a grainy look for photographs—so Alien Skin’s User Settings panel makes it easy to save and recall all settings when processing single images or batches.
Memory usage is very conservative while previewing settings, though it rises significantly when processing images. While using all 12 hyper-threaded cores of my 2010 Mac Pro on a 600 percent enlargement of a 12MP image, RAM usage jumped as high as 7GB with the Maximize speed preference, and 4GB when using the Conserve Memory option, without noticeably impacting speed. That’s all good since the application exits on completion so it doesn’t add to Photoshop’s RAM footprint.
What makes a dedicated upsampling program special is the algorithm used to interpolate information in a believable way, and a good one will accentuate details while not muddling smooth transitions. Some let you sharpen and add grain but, if the base scaling is weak, then sharpening will pick up these flaws. Noise will only hide them a little, and get worse as you scale up further. I put Blow Up through its paces with a variety of image types to seehow the algorithm performed.
Blow Up quality is very good when compared to the competition—at the top end Photozoom Pro, and at the bottom, Perfect Resize (formerly Genuine Fractals)—but just shy of being the best. In one test, a 3D rendering with hard edges, smooth transitions, and no grain, scaled up 200 percent, the result was quite good and definitely usable. The only issue was that localized contrast was too heavy in some areas, even with zero sharpening, and this resulted in some shadows and highlight areas popping out where there should have been smooth transitions.
Another test of a very detailed photo with some noise scaled up 600 percent revealed what I found to be the main flaws in Blow Up’s algorithm: it can produce a visible swimming pattern throughout very detailed images and noise tends to be treated as detail. At 600 percent scaling, there are obviously trade-offs to be made, but the pattern is predominant enough that it catches your eye and, combined with the lack of artifact reduction in Blow Up, noisy or JPEG-compressed photos can end up with more of this pattern than they should. You will probably need to put your photo or graphic through a denoise filter before bringing it into Blow Up but, with a little care taken to hand it optimal images, it will definitely result in a blow-up and not an explosion.
Dave Girard is a Montreal-based art director, 3D artist, and writer.