Sharpening for Printing - Help?!

[rkiebs]

I am an enthusiast trying to get more serious about photography, and I need some help with post-processing for print.

I am using Lightroom 3 and have been using Nik software as well. My question concerns how much to sharpen for printing. Lightroom has an embedded sharpening tool, I have Nik Sharpen, and then when I export a picture as a JPEG for printing (I do not have my own printer yet), Liightroom asks for further sharpening (based on the kind of print I want). Which do I use??

I tried to print a couple of photos (8x10) taken with my Canon D30; the photos in Lightroom looked great (sharpened with Nik Sharpen), and when I exported as a JPEG, I selected normal sharpening for glossy. When I got the picture back, it was overly sharpened and didn't look good.

What techniques do you use to sharpening your pictures (workflow techniques)? I could figure it out with trial-and-error, but it would be costly and time-consuming...help!

Sorry for the long question and thanks in advance for the help!

[teaking]

Print sharpening is device dependant so its hard to give exact figures, in general you should have an image on screen that looks over sharpened. Usualy for print sharpening your viewing at around 50% but these are just general rules.

The below are some notes I have taken from around the web when I was looking into the same thing, please be aware this is only advice and I have not tested this and it is not my own work but it may be helpful

The rule of thumb I use (one that has held up well under a good deal of empirical testing) is to aim for a sharpening halo that's somewhere between 1/50th and 1/100th of an inch in width -- the thinking being that at normal viewing distances it's too small to see as an actual halo. It follows that output sharpening must be done at final output resolution.

To accomplish this, you need to know the output size and resolution, and the way in which the output device converts the pixels into marks on paper. For example, if you're printing to an inkjet printer at 300 ppi, you want to create a sharpening halo that's about 3 pixels wide. If you're printing to a halftone printer such as a press, using a 266-ppi file and a 133-line screen, you need a halo that's at least 4 pixels wide, because each halftone dot is made up of four pixels, and you may well be rewarded if you make the halo 5 or 6 pixels wide. Output sharpening doesn't require any complex masking -- all the image-specific local concerns have already been addressed in the capture and creative sharpens -- so the output sharpening can be applied globally.

Needless to say (but I'll say it anyway), the result looks pretty ugly on screen when viewed at an Actual Pixels zoom level. You can make better judgments about output sharpening by viewing at 50% or even 25% (avoid the "odd" percentages like 66.6% because Photoshop applies heavy antialiasing to those views) If you follow the above-mentioned formula, keeping the haloes to between 1/50th and 1/100th of an inch on the final output, the results will look good.

For single stage output sharpening, the principle is generally to use a larger radius to give a more overall image sharpen and to compensate for image re-sizing that may have been done since the capture sharpening.

It is normal to set the radius first as this is determined by the intended use and the image itself. For a detailed image to be used in a book or glossy magazine where close viewing is likely, the radius should be in the region of 0.7 to 1 pixel, with an amount of around 350%. For newsprint, this is more likely to be 0.9 - 1.2 pixels because of the coarser printing dot.
Images used for larger display, posters or billboards will require a radius in the region of 1.5 - 3.5 pixels or more. This is because the resolution of the printer will be much lower and the viewing distance will be significantly greater. Thresholds for these settings have to be judged on an image-by-image basis depending on content and image noise.

[rkiebs]

Teaking - Thanks for your post...the info will certainly help me better adjust the sharpening in the future. However, I also need help with using multiple sharpening tools for output to print. If I sharpen my pictures in Lightroom/Nik, should I sharpen them again when I export the files as JPEGs from Lightroom (when selecting export from Lightroom, the program asks for additional sharpening based on the print), or will that overly sharpen the images?

Thanks!