> > From: Cory Papenfuss <[EMAIL PROTECTED]> > Date: 2006/02/02 Thu AM 11:41:33 GMT > To: [email protected] > Subject: Re: Re: MX screen in my istD > > >> The matt surface is the surface that the finder image is formed on and so > >> should be closest to the mirror. > > > > That doesn't sound logical to me. The reference plane will be where the > > screen beds against the body, which will be the upper surface. It > > doesn't matter that the image goes through the screen - it's > > transparent/colourless. As long as the gg is aligned with the reference > > plane, focus (having been so before) should be correct. Only if it is > > not bedded (and focus would vary across the frame, probably) or > > installed the wrong way round will focus be off. > > > The matte/prism side should be near the pentamirror/pentaprism, > not the mirror. It makes sense because that is a defined plane in the > camera.... the screen can be anything, so long as it's flat against that > surface.
That's what I said, didn't I? > > The only thing that bothers me with that argument is that the > index of refraction of the plastic is different from air. That must have > been taken into account in the geometry of the design. Agreed. 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.... > > 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. mike ----------------------------------------- Email sent from www.ntlworld.com Virus-checked using McAfee(R) Software Visit www.ntlworld.com/security for more information
