Output Resolution

Hey guys,
very interesting post about resolution 600 vs 300 output. Mainly aimed at people using the ipf5000. Definately worth reading. http://canonipf5000.wikispaces.com/m...e9630b35570243

Canon boasts resolutions upwards of 9600x2400 dpi (dots per inch), but that is the addressable resolution- the accuracy with which it attempts to lay down dots of ink. The relationship to the pixel resolution of the image is fairly indirect, but the optimal ppi (pixels per inch, not to be confused with dpi) is much lower. The current conventional wisdom is that the "native" resolution of Epson printers is 360 ppi, while that of Canon and Hewlett-Packard printers is 300 ppi.

If you send images that have a significantly higher ppi than the native resolution, one of two things will happen. In the best case scenario, the printer will downsample the image to a resolution it can deal with, and the difference in images printed at the two resolutions will be slight. In the worst case scenario, the printer will try to incorporate all the extra information, resulting in an image that looks blocky and pixelated.

The biggest problem with downsampling (for me personally anyway) is that it has a significant effect on sharpening. I tailor my images so that whatever my output medium, my sharpening halos are about .01 inches wide, resulting in a nice, crisp image without visible halos. On a Canon printer, that equates to a 3 pixel-wide sharpening halo (300ppi resolution divided by 100). But if I send a 600 ppi image to a printer with 3 pixel halos, and the printer then downsamples the image, it prints the image with 1.5 pixel halos, or about .005 inches, resulting in a soft, undersharpened image.

The answer is to determine the size you want the print to be, and the native resolution of the printer, and downsample the image to those dimensions before sharpening the image. For example, a 5x7 print on a Canon printer should be downsized to 2100x1500 pixels, and sharpened with 3 pixel wide halos.

It took me a long time to get my head around these concepts, and if you try it yourself, you'll see why. The resulting image looks nasty- oversharpened and pixeleated- on screen. But go ahead and send it to the printer anyway, then compare it to the images you've been printing. It's one of the biggest leaps of faith in Photoshop. It's also one of the biggest leaps forward my printed images have taken.

-Joe U.

You're right Joe, but these people were printing throught the canon plugin. Also, they were getting similar if not better results by printing same image at 300ppi and 600ppi. The advantage being you could start out with smaller initial files and still get as good a result.

Sure you can, because as I said, the printer is going to downsize the image to 300 ppi anyway. The "better" aspect stems from the fact that by downsizing in Photoshop, you retain more control over which information is and is not lost. Sorry if I didn't make that clear earlier.

-Joe U.