In preparation of an upcoming video tutorial on how to scan color film, I thought I share some recommendations for exposing negative film especially for scanning.
When shooting color negative film there is one common mantra: never underexpose your shot! As film can handle quite a lot of light this is certainly a great idea, however we need to be a bit more precise when shooting film for home scanning on a consumer scanners like the Epson V-series. When exposing negative film densities built up on the film material and the more light hits the film the denser it gets. Dense negatives contain a lot of information and tonal values, which is great, but a scanner needs more light to collect this information on the sensor. Pro scanners or minilab scanners can adjust the brightness of the light source while consumer scanners normally adjust exposure time. With increased exposure times you unfortunately produce more noise during the readout of the CCD sensor. CCD sensors are unfortunately not really good in handling longer exposures. Your final image will have a good amount of both color and frequency noise. So overexposure can be problematic for most flatbed and film scanners. There are of course great scanners designed for home use that allow adjustments of the light source and these machines are therefore better suited for scanning dense negatives.
Underexposing negatives won´t help either. The scene brightness will always be compressed when captured on film. All the tonal information will be expanded in either the darkroom or by the scanner software. Underexposing film, will capture less detail and less tonal information. The small tonal range will contain insufficient information for the required expansion and we will see digital artifacts in the final scan. In order to reduce the amount of digital artifacts it is very adviseable to scan at the highest bit depth available. Most consumer scanner have 16bit (48bit color) CCD sensors. With 16bit scans the scanner software has much more information for the expansion and will provide you with cleaner files.
When exposing film, keep your workflow in mind. While you can get away with a descent amount of overexposure when you send your film to a lab you need to be more careful when you are planning to scan your film at home. I would recommend shooting around box speed, maybe 1 stop brighter. Don´t go lower for good results! You can try to get away with a certain amount of overexposure, but avoid going too far. Besides rating your film, the way you measure exposure also plays an important role. Exposing for the shadows, a common technique for color negative film, will increase film density additionally. My experience shows, that under normal condition a Epson V700 can still handle Kodak Portra 400 rated at EI200 and exposed for the shadows. Pay special attention in situation with changing light conditions for example just after sunrise. The human eye tend to fail in these situations and we often misjudge the way light intensities change.