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Tuesday, May 22, 2007

The Art Of The Up-Res

Getting beyond the limitations of your camera's native resolution is an art and a science


I processed the 6-megapixel capture with its native resolution of 3072 x 2048 pixels to match that of the 16-megapixel resolution of 4992 x 3328 pixels using the Bicubic Smoother option of CS2's Image Size (Figure 2). Is this optimal? Should one interpolate in Camera Raw versus Photoshop? Prior to Photoshop CS's Bicubic Smoother option, there were better options for up-resing, including Camera Raw's algorithm, but not with Bicubic Smoother as an option—it was specially designed by Photoshop engineers, Chris Cox, in particular, for optimal smooth up-resing of digital images. Even Thomas Knoll acknowledges that up-resing in Camera Raw versus Photoshop using Bicubic Smoother is about a wash.

Figure 2 






ABOVE: These screenshots show the process by which Schewe interpolated the 6-megapixel image up to 16 megapixels via the Bicubic Smoother option

The 16-megapixel capture was processed with no additional sharpening and the same noise settings as the 6-megapixel capture. The results? Pretty much as one would expect, the up-resed 6-megapixel capture is a lot softer, with less textural detail. Expect miracles? That takes a little work.

The Art Of Sharpening

Both images are in need of sharpening (Figures 3a and 3b), and that's an art form in itself! I've chosen not to use my favorite tool, PixelGenius' PhotoKit Sharpener, for this example. I wanted to produce a result that anyone could duplicate so I used plain old Photoshop Unsharp Mask (USM). The images are being viewed in Photoshop at a zoom of 200%.

For USM, I used a 200% amount setting for the 16-megapixel capture and an amount of 400% for the 6-megapixel capture (Figures 3c and 3d). Both had a Radius of 0.5 pixels and no Threshold. The amount of sharpening was image-specific and shouldn't be construed to be my "normal" sharpening. I have an entirely different approach to sharpening, which will be explained shortly.

Figure 3 


















FIGURE 3a: A blowup from the 16-megapixel camera. FIGURE 3b: A blowup from the resed-up 6-megapixel camera. Whether scanned or photographed with a digital camera, an image that finds its way into a digital form needs some sharpening. For simplicity's sake (and because whole treatises could be written on sharpening), Schewe used the Unsharp Mask and varied the settings only slightly. FIGURE 3c: The 16-megapixel image got 200%. FIGURE 3d: The 6-megapixel image got 400%.

After applying the sharpening to a duplicate of the background layer set to Luminosity, further examination of the files revealed some interesting conclusions. You, indeed, can up-res a 6-megapixel digital capture and get a reasonable and useful facsimile of a higher-resolution camera from a lower-resolution camera—within certain constraints, namely, output size. The up-resing of the 6-megapixel to 16-megapixel file (an increase of 162.5%) would produce a reasonable output when printed at 16.6x11 inches at 300 ppi.



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