sorry i have been away and just spotted this. differences as follows...
1) the d40x has lesser precise controls for ISO (1/3 v 1.0 jumps in ISO). the d80 also maxes out at Hi1 which (i think) is 3200 ISO - this isnt avail on the D40/x
2) the biggest difference is that the d40/x cannot take lenses that dont have its own focus servo. this means it can only take lenses that are AF-S and NONE that are primes. the d80 can take all lenses. prime lenses, as u will learn when u take more photos are cheaper, optically superior and faster for their money.
3) WB cant be set precisely with D40 using custom colour temps (ie shooting a white card and inputing a wb temp in). this CAN be done on the D80
4) the d40/x only shows the histogram after taking the shot and NOT the RGB histogram. i suspect that this histogram it shows is only the green channel and may not be truely representative of the RGB combined channels. Of course, the D80 shows all three as well as the white.
5) the d40/x doesnt have the LCD screen on top which shows all the camera functions and settings typical of nikon cameras. this is a cost cutting feature and also one to differentiate it with the d80. i dont think this bit really matters as it shows this info on the main colour screen anyway.
6) no grid lines to measure up the horizon or vertical lines to measure up trees.... (can always correct in PS). d80 has these built in grid lines.
7) Cam530 autofocus on the D40 is inferior to the Cam1000 on the d80/d200. cam100 is very fast ! i havent read anything about the speed about the cam530 AF mechs. the d80 also has a few better focussing controls that may be relevant in varying conditions (dynamic area focusing etc)
8) d80 has bulb function (opens shutter for as long as u like). d40/x doesnt.
9) lots more nooby flash functions on the d40 - lots more advanced hard to learn functions on the d80
10) d40 doesnt have option for vertical battery/potrait grip - d80 does
11) battery in the d80 is heaps better - lasts a lot longer inbetween charges
i think that's it
