THE EFFECTS OF NIKON SCAN'S GEM SETTINGS

GEM is a software utility built into Nikon Scan used to digitally reduce the film grain seen in an image. The following case study will examine the effects of Nikon Scan 3.1's different GEM settings on the sharpness of an image.

The methodology used involves scanning the same slide five times in 8 bit mode, at 4000dpi, and in sRGB color space using a Nikon Super Coolscan 4000. One scan is made for each GEM setting ranging from "Off" to "4". The images are then cropped at "actual pixels" size, and saved out as high quality (Q=90) jpgs in Photoshop to make them viewable on the web. This system is not perfect due to the compression of the images and other factors but I believe it accurately shows the effects of the different GEM settings.

With this image, grain is slightly reduced with every increment in which GEM is increased and is virtually eliminated when GEM is set to 4. Unfortunately sharpness is also loss as the GEM settings are increased. It should also be noted that the effects of GEM seem to vary between images so images shot on different film or different exposure settings will not respond the same way this image did. For images with more pronounced grain, the effectiveness of GEM will be more dramatic as the GEM level is increased. Many images will also show artifacting from the use of GEM which is not seen here. These artifacts resemble a crumpled plastic surface when GEM is set too high.

CONCLUSION: Considering all the above, it is recommended that GEM be set to off by default but used when necessary by experimenting with the different levels to find the setting that offers the best compromise between grain, sharpness, and artifacting. Be careful to examine the effects of GEM on the final scan and not the preview since Nikon Scan does not accurately show the effects of GEM on the preview.