> > From: Cory Papenfuss <[EMAIL PROTECTED]> > > So, you'd likely > >> not be able to change the thickness *too* much. I'd bet it works out that > >> it'd have to be significantly thicker to screw it up too much. > > > > Depends on definition of significance. SMC has significant effect but is > > ~1/4 wavelength thick.... > > > I'd say SMC is on a whole other scale. The screen is thick enough > to be a "bulk transmission media." The question is whether a screen > that's 0.050" vs. 0.040" would make a noticable different in the resulting > focal point. The fraction of that distance to the transmission path to > the lens is pretty small. At least that'd be my engineering guess, but I > know little of optics... :)
Me neither but... 8-) Seems to me that quite small (0.001's of an inch) differences in dimensions or placings would have significant effects on image quality. You only have to look at the differences between samples of lenses to see that thing which appear identical can have significantly different outputs. > > >> > >> Just as a note. I'm pretty sure that when I first installed mine > >> I didn't quite have it in there right. When I actually took a few test > >> shots at an oblique angle, the screen-focus was slightly different than > >> the picture taken. I took the screen out, rotated 180 degrees (did NOT > >> flip it over. It wasn't *that far out), and more carefully put it back > >> in. Here's the result when focusing on the line between the 9 and 10 > >> towards the middle of the chart. > > > > I would think installation needs to be as perfect as the system allows to > > make it work properly. > > > It just seemed odd that I could screw it up. With the way the > screen holder pivots in place, it seems like it should either be correct, > or not. If not, the holder wouldn't close. Or it would close but not properly. Or it would close but be damaged. All the screen holders I've seen seem to be folded, thin steel, that could certainly be persuaded to close when they didn't want to. The hinges are also not formed with any accuracy. Most designs seem to rely on the screen naturally fitting to a specific place due to its design and the holder using steel's inherent springiness (sometimes abetted by real ones) to hold the whole contraption in place. The ones that are "engineered fits" are usually the ones attached to cameras that say something like "Return to service centre for screen replacement". To return to the thread subject, my suggestion would be to keep trying with the cut screen until one is sure that there is no possibility of it working. This may require more than one attempt at fitting, interspersed with focus testing. One thought that occurs to me is that the raised portions of focus aids might preclude the proper fitting against the pentawhatever in a camera that did not have these aids originally. m ----------------------------------------- Email sent from www.ntlworld.com Virus-checked using McAfee(R) Software Visit www.ntlworld.com/security for more information
