Pumping Pixels
by David Arnold & Gail Rutman
Does your DSLR produce adequate-sized images for your photobuyers? If you’re selling stock only direct to photobuyers (via PhotoSource International’s PhotoDaily or PhotoLetter market letters,
Most stock agencies and libraries require at least a 48 megabyte file (although some accept 24MB for certain editorial subjects). You could make the 24 mark with an 8 megapixel camera (since it takes three bytes to make up one RGB pixel), but the only DSLR that will give you a 48 MB file is the $8,000, 16.7 megapixel, Canon 1Ds Mk II.
Can’t swing $8,000? There’s an alternative: generate new pixels from the existing ones. This is commonly called “uprezing” (since it increases the resolution), interpolation (since it involves inserting new pixel values between the existing ones), or simply upsizing. There are a number of products you can use for this. We tested five of them: Photoshop CS2, Adobe Camera Raw (built into Photoshop), Genuine Fractals (www.ononesoftware.com, $159.95), Resize Pro (www.fredmiranda.com/software, $29.90), and the interpolateTHIS.com action (www.interpolatethis.com/actions.html, free).
We took an 18MB TIFF file from a Canon 10D (6.3 megapixels) and uprezed it four times with each of the five products. First we enlarged it to 165% of its original size to meet the 48MB requirement. Then, going back to the original, we uprezed it 200%, doubling the original width and height and quadrupling the file size to 72 MB. Then, again starting with the original file, we uprezed it 400 percent, creating a 288MB file (enough for a 27 x 41 inch print).
That’s certainly enough, isn’t it? Not necessarily. What if you want to crop the original image, using only, say, one-quarter of it (4.5MB or 1.5 megapixels), and then enlarge it to that same 27 x 41 inch/288 MB size—an 800 percent enlargement? We gave it a try. The result was softer than the other files, but for many buyers it would still be acceptable.
In evaluating the results we looked primarily at sharpness, but also at color rendition, degree of noise and other artifacts, and other quality considerations that could influence a photobuyer’s decision.
In addition to image quality, we considered each program’s ease of use and flexibility. Adobe Camera Raw only lets you uprez to three preset sizes, making it the least flexible. Easiest to use are Photoshop CS2 and Miranda’s Resize Pro, closely followed by Genuine Fractals.
Our recommendations: ResizePro consistently turned in the best results for us. But if you want to see which one best suits your style and equipment, download the free 30-day trial versions available for all but Resize Pro, and perform your own tests. You might want to skip the free one, however: it ranked near or at the bottom in all our tests, and was clumsy to use.
David Arnold and Gail Rutman are Oregon-based stock photographers and photojournalists who have been writing about photography and computers since 1980. You can contact them at www.arnoldrutman.com.
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