Paul,
To be honest, old lens designs are off my menu (fine pieces of glass though they are on the end of film bodies) as I have to assume that digital sensors have required new design of lenses. Unless that is nothing more than propaganda from those whose interest it is to persuade us so.
There's no simple answer and it varies from sensor to sensor anyway, as pixel density affects image quality. In general, the more tightly the pixels are packed the more the sensor demands from the lens.
Good tele designs typically are as good on digital bodies as they are on film bodies, but it's a mug's game with wideangle lenses because light rays hit the sensor at an oblique angle, which can lead to blurring and aberrations. Zooms are also hard to predict. If they have a small amount of chromatic aberration on film they may have unacceptable amounts with digital. Vignetting is an issue, too, but that's one area, at least on APS-sized sensors, where the results on digital can be better than on film.
FWIW, the lenses you had (28mm f/2.8, 50mm, 85mm f/1.8 AF-D and 105mm f/2.5 Ai ) would have been very good to excellent on a modern digital body.
Alas, Nikon is off my menu for combined reasons rather any one individual limitation. The omission of motors from camera bodies may or may not be justified or simply marketing pecking order, I don't know. My collection of classic lenses (all sold earlier this year) would not meter on anything below the D200 for no better reason than... marketing pecking order. Nikon did not have to cripple the D80 from providing metering of non DX lenses. My SB-28 flash was as perfect as the day I bought it but worthless on a digital body where it would not provide TTL. I do not understand why either a firmware upgrade or even different settings to take account of crop factor could not be worked into it. Instead I was expected to buy another £200 flash gun.
Price is very important in the entry-level D-SLR market, so anything that can cut costs (loss of full compatibility, reduced features, use of cheaper labour, etc.) is sought to be competitive. A Nikon D40 doesn't compete only with a D50 or D80; it competes also with the Canon 350D and Pentax K100D. I realize that having D200-level compatibility on a D40 may add only 40 pounds to the overall cost of the camera, but that 40 pounds might make the difference between someone buying a 350D over a D40, if starting from scratch.
The other thing you have to remember is that your F3HP is a pro camera, and your F90x a serious amateur camera, so you may have become used to brick shithouses that were designed to be used for decades, not a plastic contraption Nikon hopes you'll dump after a few years.
Basically, enough was enough and I sold up and got out as I no longer trust Nikon. An esteemed London dealer 'kindly' offered me £300 for a job lot of items which of course had cost me many times more, at least half of which had been sold to me by that dealer. Their per item price certainly woke me up. I made about £900 selling privately instead (this included F90X, FM2N, F3HP, 50mm & 85mm 1.8 AF-D, 105mm 2.5 Ai and 28mm 2.8 Ai-S, SB-28, Billingham 335).
You'll always make more in a private sale because the shop wants to make money on your traded items. This is nothing new, though digital has made things worse.
As I have said before, to start again it feels instinctively that anything you buy today is money down the drain, such is the pace of evolution in digital. As such, vfm, using that term relatively in a world of obsolescenc appear to point me to Hence, spending low would seem to get one K200D, E520 or indeed E420 as suggested.
Digital moves quickly to be sure, but there's no reason why someone can't take good pictures with an older camera. Cliff's D3 runs circles around my S5, but for my pictures and needs I'd see little improvement in getting the latest and greatest from Nikon. It would be a different matter if I routinely shot at 3200 ISO and 8fps, but I don't.
Joe
