If you want to do prints whose resolution is larger than that of your digital camera, you could leave the job of digitally enlarging the photos to the printer driver. But in that case you can not be sure of the quality of the prints. Many graphics applications offer an Image Size or Resize feature for enlarging images, but if higher quality is your concern, you should look further. Especially if you want to do relatively large prints, it is essential to use a special tool to produce high quality enlargements.

How do the image sizing features in graphic applications compare? Photoshop's Bicubic option is OK for upsizing images up to 200%. The new Bicubic Smooth option in Photoshop CS is even better for bigger enlargements. Unfortunately Paint Shop Pro (up to the current Version 9.0) produces blocky results when upsizing images, because it offers no real bicubic method. So better only use its Resize tool for downsizing images. PhotoImpact on the other hand offers a true Bicubic resize option which looks better than Photoshop's Bicubic method, but not quite as smooth as Photoshop CS's new Bicubic Smooth option. Finally, the popular freeware IrfanView (Version 3.92) offers a Lanczos resizing option which uses too few sample points and therefore can produce an unwanted shadow pattern in some images. So it is better to use the Bell or Mitchell option which are comparable to Photoshop's Bicubic Smooth option.

RDK's SmarterResize consists of two automation plugins, which completely rely on Photoshop's Image Size tool. The Web plugin lets you enter the new size in pixel units while the Print plugin lets you enter the print size in inches. As Photoshop's Image Size tool offers the same and even more options, I can't imagine that anyone may want to use this product, even if it only costs $5. Verdict: 0 of 5.

As an automation plugin Fred Miranda's Stair Interpolation Pro also uses Photoshop's Image Size feature. The trick is that it increases the image size in 10% steps and not just in one step. As a result the output has a better local contrast and is smoother than a one-step-enlargement, but if compared to the Lanczos interpolation of some other plugins, it looks as if the details were smoothed a bit too much. Stair Interpolation Pro offers three sharpening and three quality settings, but no preview. Verdict: 2 of 5.

Resize Magic from F-Soft is a filter plugin without preview that needs to be applied two times. At first it stores the image data to an internal buffer, then you have to enlarge the image to the desired size in your graphic application, and finally Resize Magic applies the resized image with a selected sharpness setting. Resize Magic uses Lanczos interpolation which is somewhat better than the standard bicubic method used in Photoshop. Verdict: 2 of 5.

OutdoorGrace ResizeIT comes as an export plugin that lets you save the resized image in various image formats. It offers several interpolation methods, including two proprietary methods, which aren't as good as the offered Lanczos and Cubic Spline Fitting methods. ResizeIT lets you choose the number of source pixels which can help to increase the resizing quality for some images, but also increases the rendering time dramatically. Unfortunately all methods, except the proprietary ones, produce a pixelated frame around the image. Hopefully a future version will have that bug fixed. Verdict: 2 of 5.

X-File from Human Software is a filter plugin that saves the resized image as a TIF file. That means that you have to reopen the saved file, which is a bit inconvenient. In addition to known methods like Lanczos it also offers its proprietary X-File method, which is a touch too smooth, but otherwise good quality. Luckily there is a preview to help you to choose the most suitable interpolation method, but there are no adjustable parameters. Verdict: 2 of 5.

SmartScale (discontinued now) is delivered as an automation and an import plugin. It offers a large live preview and four combo boxes with parameters for adjusting the output quality. If the Edge Contrast parameter is set to "High", SmartScale tries to redraw the edges which can make the image look like a drawing. Activating Extreme Edges turns the image almost completely into a water painting. Using both settings seems only advisable for enlargements up to 400%. All in all, SmartScale's results are slightly better than those of Photoshop CS's Image Size tool. Verdict: 3 of 5.

Foto Power Zoom from DataBecker is a standalone program that is available in German language and will hopefully become available in English, too. There are various resizing methods along with its proprietary Visual Displacement method. It offers several parameters for adjusting sharpness, contrast and details. Foto Power Zoom manages to produce enlargements with good contrast and detail. Because of its extremely low price (approx. $3.50 for the German Version in October 2004) it will be a tough competitor for SmartScale and PhotoZoom. Verdict: 3 of 5.

Visual Comparisons Please click on each image to see the full size image. You can't see any difference from the thumbnails.
Original Image upsized by 800% without interpolation.	SmartScale tends to produce too painting-like enlargements at certain settings.	PowerZoom produces good contrast, but some edges may look a bit rough.	PhotoZoom creates good results, but sometimes they are too colorfull around the edges.	A sharp and detailed output are Genuine Fractals' strength, but you may need to get used to the fractal-like look.

PhotoZoom (previously known as S-Spline Pro) from Shortcut is available as a standalone application and as an export plugin that will save the output as various image files. Among other methods it offers a proprietary S-Spline option which usually produces the best results. There is a Unsharp Mask feature and three parameters for adding grain and increasing edge contrast. However, with increasing edge contrast the edge colors become unnaturally saturated. So the interactive preview is a big help for achieving balanced results. The results are somewhat sharper and more detailed than those of SmartScale. Verdict: 4 of 5.

Genuine Fractals (now called Perfect Resize) comes as a file format plugin. To enlarge images with it you have to save the image in its STN format firstly. When opening the STN file again, you can enlarge it to your desired image size. Genuine Fractals is quite unique, because it doesn't use standard interpolation methods like other plugins. With the help of a special fractal algorithm it produces photo enlargements that are sharper and more detailed than any of the other mentioned tools. Evenmore, you are still able sharpen the enlarged images, which isn't possible with other tools. Still, its output has a fractal-like look which may not be everyone's taste and for some photos you may wish to get a more softer enlargement like that of PhotoZoom. Genuine Fractal's preview works similar like that of X-File, but there are no options for adjusting the output. Verdict: 4 of 5.

Other newer tools:

Zoom Engine (Verdict: 3 of 5)

Alienskin Blow Up (Verdict: 4 of 5)

This article was published in Issue 8 of the Digital Photography Techniques Magazine. It was slightly updated for The Plugin Site in October 2004.