Sharpening Preview


Today’s Question: I know that everybody states that output sharpening should be evaluated at 100% zoom. In the “old days” I understood that Photoshop for various technical reasons could not accurately render odd zoom percentages. Since then with OpenGL and new video cards, and inputting one’s actual screen resolution to Photoshop, has this changed? It would be very useful to be able to use the Print Size zoom setting to at least get some idea of finished printed product even though it may not be 100% accurate because it’s easier to get the total feel of the image than scrolling around at 100% zoom.

Tim’s Quick Answer: Photoshop does provide more accurate image previews at “odd” image sizes than it did in early versions, but I still recommend previewing the sharpening effect at a 100% zoom setting to get the most accurate preview of the actual sharpening effect. That said, the best way to evaluate the sharpening for an image is to review the final output, such as a print.

More Detail: Modern high-resolution displays, along with updates to Photoshop, have provided more accurate image previews at any zoom setting. However, I still recommend evaluating the actual sharpening effect at a 100% zoom setting (or the Actual Pixels setting in Photoshop).

Even at a 100% zoom setting, however, there is still some “translation” involved when it comes to evaluating the sharpening effect for a photo. It takes a bit of experience to be able to anticipate what an image should look like on the screen in order to produce a great print.

So, first off, I recommend using a 100% zoom setting when you are actually adjusting the settings for the sharpening filter you are applying (such as Smart Sharpen). Of course, you can then use the Print Size zoom setting to get a sense of the actual print size, and a reasonably accurate sense of the sharpening effect. Just be sure to enter the actual pixel per inch (ppi) resolution of the display. You can calculate this value by dividing the number of pixels across the display (based on the resolution setting) by the number of inches wide the actual display is.

The Print Size zoom setting is still a reasonable way to evaluate the sharpening effect, but I do consider the 100% zoom setting to be better. But again, you really need to make a print to determine whether the sharpening settings were optimal for the image.

Sharpening for print is especially challenging because you are evaluating the sharpening effect on a monitor display, but the final result involves ink on paper. This is further complicated by the fact that different papers will react differently to ink, such as a greater absorbency with non-coated matte papers.

Ultimately, the image preview is helpful for evaluating the sharpening effect, but direct experience printing your photos will help you get a better sense of what an image should look like on the screen to ensure an optimal print. For example, with matte papers you often need to sharpen to the point that the image looks over-sharpened, in order to get a print that looks optimal.