PhotoZoom Pro: perfect image resizing?

Ultimately the fundamental difference between vector and bitmap graphics is that the resolution, and so final quality, of the bitmap image is fixed. Scale a resolution-independent vector image up to the size of a football pitch and it will stay as pin-sharp and perfect as the original; scale a photo and it won’t.

This difference might seem intrinsic and unavoidable, but there are a number of software applications that promise to bridge the gap and maintain sharpness while letting you resize your images up to a massive 1 million x 1 million pixels. So do they deliver, or are they selling snake oil?

It’s first worth pointing out that Photoshop itself lets you scale up your images based on a choice of interpolation methods with its Image Size dialog. Set the percentage size of your image to, say, 150%, choose the Bicubic Smoother interpolation method, hit OK and then apply some unsharp masking and the result may well be acceptable. Applying multiple smaller enlargements also helps maintain quality if you have the patience. However, with larger increases the image inevitably pixelates and blurs, and any compression artifacts become distractingly obvious.

So what more can be done? In the past I’ve used Genuine Fractals (now developed by onOne and called Perfect Resize) and Alien Skin’s Blow Up and they both have points in their favour – for example, both offer photo wrap and superior cropping capabilities. However recently I was asked to take a look at BenVista’s PhotoZoom Pro and it is now my preferred option.

The full details are in my PhotoZoom Pro 4 review, but to my mind the program has two main advantages. The first is its interface. Both rivals are designed to run within Photoshop, but PhotoZoom Pro, while beautifully and tightly integrated with Photoshop (including support for layers and HDR images), is essentially a full-blown standalone application. This is useful in its own right, for example when batch resizing, but the biggest difference is that the program is both fast (with multi-processor support) and streamlined. By comparison both Perfect Resize and Blow Up seem to be making a bit of a meal of the job in hand as if to justify their existence.

PhotoZoom Pro’s biggest strength is the most important: quality. There’s no doubt that both Perfect Resize and Blow Out’s algorithms offer superior resizing to Photoshop’s, but the differences are generally subtle. By comparison, PhotoZoom Pro lets you choose from a whole host of industry-standard algorithms (Bicubic, Lanczos etc) as well as three versions of its own patented algorithms – S-Spline, S-Spline XL and S-Spline Max – and in each case the difference in end quality of its proprietary resizing is absolutely clear.

That said, it’s important to realise that no software can produce miracles. You can do lots of things to improve apparent end quality – maintain sharpness, reduce compression artifacts, generate pseudo detail, add photo-grain and so on – but there’s no getting away from it: you can’t retrospectively add back real detail, the pixels that weren’t captured in the original image. Enlarge by a massive amount in PhotoZoom Pro and the results inevitably look “plasticky”.

However this slightly artificial, filtered look is still a lot better than the alternative. PhotoZoom Pro 4 can’t produce miracles when it comes to image resizing, but it does work wonders in terms of damage limitation.