How do you optimally resize and sharpen images for printing?

Question

What is the best way to get the clearest, sharpest print without pixelation or blurring? I have tried some sharpening techniques in Photoshop, however they are geared towards sharpening for viewing on a screen, and do not generally produce great print results. Unsharp masking does not seem to produce clearer results, as it generates more psuedo-noise, and that sometimes reduces fine details

I am an avid user of Adobe Lightroom, and I use it extensively to process my work and generate prints. I am not particularly impressed with the print quality from Lightroom. Despite using custom ICC/ICM profiles tuned to my specific printer (a Canon 9500 II) and the specific papers I use, my photos tend to lack in the area of sharpness. Lightroom also seems to have some limitations on its maximum print resolution, defaulting to 240ppi, and topping out at 480ppi. I believe my printer has a standard resolution of 300ppi, and a native resolution of 600ppi, however there does not appear to be much of a difference at either 240 or 300 ppi when printed from lightroom. I am also looking to get an Epson 3880 in the future, and I believe its native resolution is 720ppi.

I've heard of qimage, however I did not have a chance to fully explore its options and resulting quality over the 14-day trial period, and I am not sure its worth the $90 or so to buy it. (If it is worth it, I may just go with Qimage.)

Most of my prints are from 12.1mp Canon RAW files generated by my 450D, rendered through custom Hahnemuehle ICC profiles for Canon papers (fine art, museum, satin or pro photo glossy), which are really just Hahnemuehle in disguise. Color tones are great in general, perhaps lacking a bit in contrast when printed on fine art or museum paper. The images definitely seem lacking in the sharpness area...details visible in smaller on-screen versions just don't appear as striking or evident when printed, and fine edges on screen often appear softer or even blurred when printed.

Answer 1

Unsharp mask works just fine when sharping for print, the original method was actually used when creating prints in a darkroom. You just have to know how to adjust the parameters for the specific resolution.

A good base value for the radius is 0.1 mm, which you have to translate to a value depending in the resolution:

radius = 0.1 mm * ppi / 20

So, for images intended for screen, which has a resolution around 100 ppi, you use a value around 0.5. For an image printed at 300 ppi you use a value around 1.5.

To get an approximate preview of the effect, you can zoom the image according to the resolution. An image to be printed at 300 ppi can be viewed at 33% on the screen to see roughly what the sharpening will look like.

Answer 2

The ICC profiles are not really related to sharpness, they are used to get correct color.

As far as sharpening goes, you want to over-sharpen a bit from where you would normally for screen viewing, because the pixels are more obvious on screen. I tend to go about 10% farther in my sharpening when I am planning to print. Also, in photoshop, I always sharpen as the absolute last step because you lose quality when you sharpen as an intermediate step, and other changes can have an adverse effect on the detail. Also, I tend to use "smart sharpen" tools, which try to focus the sharpening effects on high contrast areas, and leave flatter areas (skies/skin/etc.) alone. This helps to decrease the noise added while still sharpening the areas that actually make a difference.

For the resolution, your best bet is to sharpen at the resolution of the printer. By this I mean if your printing service's print resolution is 300ppi, use 300ppi. Anything else will be resampled to 300ppi for printing and that conversion can have an effect on the quality. If printing at home (as you are) then keep in mind the differences between dpi and ppi.

Your Canon printer has a native max resolution of 4800x2400dpi, 10 ink colors, and 7680 print nozzles... which all leads me to think that the native resolution is a multiple of 150 (4800*2400)/(10*7680)=150... so, either 300, 450, or 600 are reasonable. I would guess that the best quality print would be achieved at 300 or 450ppi.

Answer 3

Google NIK plugin is free now. It comes with an output sharpen and allows you to select the viewing distance of your print as well as different settings in regards to print resolution, etc. NIK was $150 but Google now offers it for free. After installing it the options will be located in the filters menu. Pretty handy.