Once again I got tempted into replying :) K bodies have dimmer focusing screens than M bodies. I own a K2DMD and several M and LX body. The LX is brightest and easiest to focus.
K bodies have older technology groundglasses. These are dimmer and more cluttered than these found from M onwards. The groundglass portion is divided into two portions on some "pro" K bodies (KX,K2,K2DMD afaik): central fine matt circle and less fine fresnel surrounding which fills the rest of the frame. The central fine is good for fine focusing if the focusing aids cannot be used because of insufficient image detail or features or too slow lens. Based on my experience: best viewfinder - LX. bright, features additional condenser above screen (UNLIKE all other M & later bodies) to which LX screens are computed for with it in mind (other screens in the LX give dimmer corners). second best - MX. Higher magnification than LX by 0.05, but viewfinder not as good in the corners (the LX finder is sharper in the corners). Also, it's good to install a new screen in the MX (requiring either recalibration of the meter or deliberately setting iso to lower). I like the MZ-M's screen there, whose focusing aids don't blacken out even with 5.6 lenses (especially useful with screwmount wides which are used stopped down via the adapter and 400/5.6 lenses), unlike LX/MX default screen's focusing aids. But the MZ-M has slightly worse microcontrast. But it's brighter. I found it the meter had to be set to "overexpose" 1/2 stop. ME-Super: nice viewfinder too. But can't interchange screens. Still quite brighter than K series. K series - good with fast lenses. Is dim but still very usable in normal light. But for available light - no no. Same for the Spotmatics. For available light with fast lenses - it's sort of unusable. I have Spotmatic, K2DMD,ME-S,MX,LX and other cameras not from Pentax, and I shoot a lot in available light. The Spotmatic had worst screen for this (I exchanged it for another camera's screen, but with recalibration of focus). What's good about lasermatte screens (M and later) is that you can focus and see image detail all over the frame, unhindered by fresnel rings. What's bad about older screens with traditional fresnel lens builtin is that you can't focus well in the corners of the frame. In my opinion, Pentax's screens were not very good until the M series for available light. For plenty of light all screens are good. That's because Spotmatic and K bodies screens use two parts - a fresnel with another groundglass/fresnel on it, causing visible fresnel lens rings and worse brightness (but the traditional groundglass they employ makes very fine focus assesment possible in good light. I use a Spotmatic screen as the groundglass on film plane with which to check accuracy of focusing system). The M and later use single screen which combines all of these, produced by laser technology. The latter the better (but the AF screens are too much bright, making manual focus worse). That's all :) I would say if you photograph landscapes, in daylight, etc, get the KX - it's heavy but good old brass and glass (the K2DMD - another brass one - is real joy to use), offers true MLU. If you shoot a lot in available light or quick focusing reportage, get the MX. It's smaller, quieter and MLU can be engaged via the MLU trick. And the screen is better. Best regards, Frantisek Vlcek
