Cameras: Why we use Analog instead of Digital

To reduce costs, many video acquisition systems for behavioral testing use consumer-grade digital cameras with FireWire (IEEE-1394) connections to the computer. We prefer analog (rs-170) cameras combined with a dedicated frame grabber. Analog cameras have auto-iris lenses with large numerical apertures, and large, sensitive sensor chips. As a result, the image quality is incomparably better, especially in dim light, where many rodent behavioral experiments are performed.

At high ambient light levels (>250 Lux, which is comfortable for reading), digital and analog cameras perform similarly, although the digital camera's image is a little flat from saturation.

Since rodents are more fearful and less active in bright light, many behavioral experiments must be performed at lower illumination levels. Below are images taken at low photopic illumination, similar to late dusk when we just start to lose our sensitivity to color (< 5 lux). Here, the digital camera's image washes out, even with optimal adjustment. The analog camera -- without any adjustment -- still gives a snappy, high-contrast image. It will do so in even dimmer conditions.

High-quality digital cameras will perform as well as the analog camera shown here, but they cost 5 to 10 times as much as consumer-grade digital cameras.