The Nikon D40 is an attempt by the massive camera maker to introduce digital SLRs to the mass-market with a more affordable price. Falling on the lower end of the high-end D series from Nikon, the D40 can be seen as the D50's smaller sibling. Despite being smaller and less expensive, Nikon has taken the time between the earlier D50's release, and the more recent D40 to upgrade various technologies making the D40 quite comparable to the more expensive D50. In fact many of the technologies incorporated in the D40 are inspired from the higher end D80 and D200 prosumer/professional grade cameras.
Notable features of the D40 include the same Nikon processing engine as in the D80/D200, in-camera retouching, help suggestions in the viewfinder, SDHC support, and an unlimited 2.5FPS continuous shooting mode. Note: SDHC (Secure Digital High Capacity) is a secure digital card format that allows for capacities beyond 2GB. ISO sensitivity ranges from 200-1600 and can reach an equivalent of ISO3200 with the HI 1 functionality.
One of the main differences with this D40 SLR and the other high-end models is that the camera does not contain an external focus pin. What this means is that only certain lens, namely AF-S and AF-I lenses, will be able to focus on the D40. Normal lenses will only be able to use the computer focus, not adjust the optical lens focus itself.