| Author |
Message |
    
Gordon
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 27, 2006 - 09:51 am: | 
|
Hello.
Can I just replace a focussing screen in a TLR viewfinder even if the thickness of the glass isn't the same, or will I have to readjust focussing after having replaced the screen?
I actually don't quite understand where the camera registers the picture, where it is projected (where the focus is measured) on the screen... is it on the top surface (the shiny side) or the on the bottom surface (the mate side)?
If it's on the top surface, then the thickness of the screen wouldn't matter, would it?
The bottom of the finder frame has springs that will adapt to the new thickness, so if the image is actually "created" on the bottom surface, then the focus would have to be readjusted, or do I get this wrong?
By the way, is shiny up and mate surface down the correct way round?
Thanks for any help. |
Ed
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 27, 2006 - 09:58 am: |
|
the focus surface is down, matte, side. Thickness should not be an issue. |
Wayne
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 27, 2006 - 04:15 pm: |
|
If it's a Rollei with a removeable finder the thickness shouldn't matter, so long as it fits in the holder. For these models the the lower side of the screen is held in a fixed position by the springs (which are above the screen). For the older non-removeable hood models the springs are below the screen and push it upwards, so the position of the bottom surface varies with screen thickness. If a replacement screen is thicker than standard you have to adjust the viewing lens; if it's thinner it has to be shimmed or the viewing lens adjusted. |
rick
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 27, 2006 - 04:24 pm: |
|
That's not correct: the focusing surface is on the bottom, but the registration surface is on the top, so the thickness does matter.
I have measured the thickness of Rollei focusing screens as 1.2mm (but I'm not sure if all are the same). Depth of focus of the Rollei lens wide open is about 0.2mm, so if your new screen is at least that close to your old one you can use it without readjusting focus.
If you do have to readjust focus, there are 2 ways to do it: if the new screen is thin, you can place shims between the screen and the frame, or if it's thick you can shim under the mounting flange of the hood when you reinstall it.... or, you can do it the "proper" way by removing the front fascia panel and rotating the viewing lens to the proper position for the new screen. It's not prohibitively difficult.
(okay, shameless plug here: i sell replacement screens for these cameras)
rick : ) = |
rick
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 27, 2006 - 04:25 pm: |
|
Sorry, Wayne, my comment was in reference to the previous post. I'm a slow typer. |
Gordon
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, May 28, 2006 - 09:32 am: |
|
That's what I thought, I just wanted to have it confirmed. Thank you all! |
|
