RB67 Focusing screens

[thisismyname09]

My rb67 came with the standard #1 matte focusing screen, and I recently bought a #5 "crosshair" screen. I'm not exactly sure how to use the crosshair to focus, but I've noticed that the screen seems to cause some pretty intense vignetting. Is that normal? Do the other screens with focusing aids cause vignetting?

 

[Perry Way]

I have three screens. Some are brighter some are not. I'm not sure which one the crosshair is, but I know I have one that has a fesnel lens on the backside and that one is darker at the corners so maybe that's what you're experiencing. That is a behavior of fresnel lenses in general. Brighter in the center, darker in the edges. But vignetting? Haven't seen any areas where its cut off to black on any of my screens.

 

[thisismyname09]

It really only cuts to total black in dark settings and/or with a dark lens. In daylight it's not black, but noticeably darker. Which screens that you own do not do this?

 

[Perry Way]

my favorite is the grid. it helps me compose much better lining horizontal or vertical things up to be 90 or 180 degree perfectly. that one has just a simple frosted surface and seems to be the most even. i like that screen so much i don't even use the other two anymore.

 

[juan]

I like the grid, too. At the time I was experimenting with golden mean sized prints, I removed the screen and put a couple of pencil marks on the ground glass side to mark off the print size.
juan

 

[removed-user-1]

I believe the crosshair screens (by Mamiya and other makers as well) are designed for parallax ("knife edge?") focusing in high-magnification viewing such as astrophotography and macro work. Somewhere I have a similar screen for the Nikon F, and it vignettes in the same manner you describe. Here's a webpage that describes the focusing method with the Nikon screen: http://usuarios.uninet.com.br/~debellis/knife_edge.htm.

 

[stradibarrius]

Here is a link to the Mamiya page that describes the different screens. http://www.mamiya.com/rb67-pro-sd-accessories-focusing-screens.html