Tuesday, November 29, 2011
The Right Resolution
The conventional wisdom says set 300 dpi and forget it, but it turns out that there’s more to optimizing image resolution for fine-art printing
|This Article Features Photo Zoom|
In Figure 5, the image is printed with the image's native output resolution of 236 ppi. In Figure 6, the image is printed at the upsampled resolution of 360 ppi from Lightroom. One pretty obvious difference is the way the light and dark diagonal edges in the building show a jagged edge in the native resolution, while the edges are smoother in the upsampled print. Remember that what you're looking at here is at about 10x life-size. However, I can see the difference with my naked eye (Figs. 5 and 6).
The Canon Results
The native resolution image of the Canon print shows the same jagged-edge problems that the Epson print showed. You might think that, since the Canon uses a lower 300 ppi output resolution, there wouldn't be as much difference when upsampling. However, upsampling from the native 236 ppi to 300 ppi does improve the edge detail (Figs. 7 and 8).
My Conclusions So Far
From this test, I've concluded that upsampling to the reported resolution of the printer will produce better results than printing with the native resolution of the image. The upside is a reduction in artifacts caused either by the print pipeline or the dither of the printer. The only real downside to doing the resampling in Lightroom is that the processing time for the print-spool file is a bit longer. The actual print time, once the printer starts printing, seems the same. I'll admit that printing with the bi-directional off is slower by a factor of two—twice as slow. I would normally suggest printing with bidirectional on for these resolutions.
The image in the Lightroom 3 Print Module.
But Wait, There's More
Saying you should upsample to the reported resolution of the printer when the native resolution is under that of the printer is fine. What about when the native resolution is above the reported resolution of the printer? Should you downsample to 360 ppi for Epson and 300 ppi for Canon printers? I answer with a resounding NO! The only time you should consider downsampling for output is for the web or if you're supplying CMYK output. In the case of CMYK output, most RIPs will do their own downsampling of an unknown flavor and suffer potential softening of the image.
The Epson pro printers have an option in the print driver called Finest Detail. When that option is checked, the driver actually reports its resolution to be 720 dpi. The Canon also can report to the system as a higher-res 600 dpi printer. In the past, Epson has told photographers they didn't need to use the Finest Detail option when printing. Epson says that it's useful for vector graphics and type, but not images. I beg to disagree. I decided to go about proving that upsampling to 720 ppi for Epson and 600 ppi for Canon printers can be useful.
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