Lenses work differently with digital than they did with film. Not on the functional level, mind you (although the mechanical aperture ring does seem to have become a niche and not a given), but optically. Digital is apparently more demanding of lenses, for a few reasons.

1. Sensors are flat. Film was, well, mostly flat, but all of you have handled negs know it wasn’t entirely flat.The completely flat digital sensors reportedly have a way of pointing out optical flaws film never would have revealed. At this point, however, these problems seem to have largely been remedied by all the major lens players.

2. Sensors don’t like oblique light.Thanks to the way pixel wells work, the more light that hits the bottom of the well the better things go. This has lead to a new range of designed for digital or digitally integrated lenses (Tamron, for example, makes these in a selection of Canon lenses and Nikon lenses, and Olympus digital cameras had their lenses designed ground up for this). Basically, they’ve got reworked optics that try to project the light as perpendicular as possible onto the sensor. My diagram there gets the idea across, but please don’t consider it a technically accurate diagram.

There’s one more point, and that’s resolution, but that’s a big topic that I’m not willing to tackle inthis post. It has to do with pixel concentrations and lens resolving, but the general walk-away idea is that the higher your pixel count per area the better the lens you’ll need.