Hello Steve,<br><br>First the vignetting. It is the viewfinder image only that is affected, not the image on film.<br>Vignetting is visible using lenses of 120 mm and increases as lenses get longer. However, maximum vignetting is reached with 250 mm lenses, it doesn't increase with lenses even longer.<br>Vignetting also increases when focussing closer. So *all* lenses will show some if enough extension is added.<br>Vignetting is caused by the mirror (too short, so it will not hit the rear of the 80 mm lens when swinging up), and is not affected by aperture. Hence it is visible at all apertures.<br>Why not consider a CW instead of the CX? The mirror in the CW is larger (possible because it moves backwards, away from te lens when swinging up).<br>All ELX and ELD models have a large enough mirror too, so do not vignet.<br><br>Next, the mirror lock up. Both C(...) and EL(...) models have mirror pre-release. None of these models has true mirror lock-up. The mirror always has to come down after the exposure is made.<br>The EL(...) models "pretend" to have a lock-up (mirror stays up between exposures) mode (called "AS"), but what actually happens is that the mirror actually comes down and flips up again, and ends up in pre-released state (i.e. with the mirror up. Mirror induced vibration can not (!) be avoided in this mode.<br>You need a (discontinued) 2000-series camera to have true mirror *lock*-up.<br><br>The 500 CX cameras were all supplied with Acute Matte screens (the first, non-"D" generation). However, since the screens are freely interchangeable, that does not mean that a 500 CX camera found today still has an Acute Matte screen installed. So beware.<br>You can recognize Acute Matte screens by the (four line) reference cross: on old style screens the lines are black ink, on Acute Matte screens they are extremely thin raised parts of the plastic underside of the screen. When placing a screen flat on a surface, the reference cross on old style screens remains clearly visible. The cross on Acute Matte screens becomes virtually invisible.<br><br>And last, your choice.<br>Why not consider a 503 CW instead of the set of two cameas you mention?<br>The CW has the better (non-vignetting) mirror, better anti-stray light coating, has TTL-flash control too, and can be equiped with a motor if and when you want it (with wireless remote control). It does all your chosen set does.