Making HUGE prints that look great from digital files with a limited amount of data can be a challenge. Stair Interpolation is a Photoshop action available at www.fredmiranda.com that will enable you to make smoother prints at very large sizes. It seems to produce smoother edges than other methods I've tried at very large multiples of the original file size. Below you will find a comparison of the different image size change methods Photoshop offers. I took a sample image, the first photo below, and "blew it up" using Stair Interpolation, and the three methods Photoshop 6.0 allows when you select "Image - Image Size." I recently made a four foot by three foot poster with a photograph I took on 35mm film and scanned on a Nikon LS-2000 scanner, printed on a large-format Epson digital printer, and the result was stunning, with no visible pixelation even under close inspection. Below you can see some test samples of another image and the results of different methods of enlarging it 16x its original size.
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| The original image before enlarging, with text layered on in Photoshop. This and all following images were treated exactly the same except for the method of enlargement, which is noted. |
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| Detail of original image "blown up" 4x and 4x again, for total 16x enlargement, using Stair Interpolation. Note the smooth contours and color gradations possible using this action to enlarge files. There is some artifacting visible near sharp edges, but for most purposes there is less than from Photoshop. |
Detail of the original image "blown up" with the Navigator Window 1,600%, showing extreme pixelation resulting from simply making the original data display at a larger size. This is why you can't "simply" enlarge a scanned image without using some kind of smoothing or interpolating program. |
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| Enlargement made using Photoshop's Bicubic method. Note the slight, but visible artifacting near contrasting edges, as well as the slightly more noticeable distortion of those edges when compared to Stair Interpolation. | Enlargement made using Photoshop's Bilinear method. Note the obvious pixelation at the sharp edges when compared to Stair Interpolation or even when compared to Photoshop's Bicubic method. |
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| Enlargement made using Photoshop's Nearest Neighbor method. Not the extreme pixelation visible along contrasting edges, as well as in the large colored areas. |