Gloss Differential

Technique - Printing  Comment
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Gloss differential is an uneven reflectance of the surface of a print. In inkjet printing, very dark colors are produced with substantial amounts of ink while very light colors are produced with little or no ink. This can produce differences in reflectivity throughout the surface of a print in many images. While this is not an issue for most matte surfaces, it can be distracting when looking at glossy prints under specific angles of light.

Recent ink technology includes additives designed to reduce gloss differential to produce more even print surfaces. In addition, some separation routines reduce it even further. Epson printer drivers include two features in their Advanced Black and White mode, Highlight Point Shift and Highlight Tonality slider, that can be used to reduce gloss differential. Running these settings to a maximum virtually eliminates gloss differential. Because clear and very light black ink are used in these delicate areas, this darkens the print only slightly. You can compensate for this by lightening the file before printing.

How can you identify gloss differential? Make a print with very bright highlight areas. Look at those printed areas under bright light while varying the angle of the surface of the print and compare the reflectance you see there to darker surrounding areas.

What can you do to reduce gloss differential? Use the latest inksets. Optionally, use the most recent black and white software routines to reduce it even further. (Epson’s Highlight Poiint Shift is designed for this.) Hold your highlights slightly full to avoid paper white, which will be less reflective. Finally, consider spraying, varnishing, or waxing the surface of your prints.

Read more with my online Printing Resources.

Learn more in my digital photography and digital printing workshops.

Bronzing

Technique - Printing  Comment
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Bronzing is an iridescent flash of color, typically bronze, produced when viewing prints under varying angles of light. It’s produced by pigmented ink’s tendency to refract light. It’s most visible in black and white prints but affects color prints as well. It affects glossy surfaces almost exclusively.    

Optimum choice of ink and precise placement makes the difference. Recently, new separation routines and screening algorithms have been devised to place droplets of specific ink colors, in specific patterns, in combination with other inks to dramatically reduce bronzing.

How can you identify bronzing? Look at the surface of a glossy print in near direct light. Change the angle of the print and look for a flash of bronze near areas of glare.

What can you do to eliminate bronzing? Choose the best inksets and drivers. (Optionally, print on a matte surface.) This will all but eliminate bronzing in your prints.

Read more with my online Printing Resources.

Learn more in my digital photography and digital printing workshops.