RB67/RZ67; special focus screen for macro?

[max_ebb]

Someone was just telling me that there is a special RB67 focus screen for macro work. This doesn't make any sense to me. I don't know what the difference could possibly be. Is the guy completely mistaken, or is there something I'm missing? Anybody else heard of such a thing?

 

[SLane]

Mamiya has an updated site, Mamiya.com. It shows a screen called a CROSS HAIR screen that is more suited to macro than other screens. I have never used it, so I can't say if it is better. (I use a RZ67)

 

[Marco Gilardetti]

Max, in macrophotography or any other work in which extremely-low light or narrow-aperture issues arise, most of focusing-aid devices become unuseful (microprism and split image turn totally black, the fresnel lens appears as a confusing pattern, ground glass is too dark to see anything, etc.).

In these cases, special screens like the said "cross hair" may be useful to get precise focusing. These screens have a central circular portion which is completely transparent (that is "not ground"), except for a very thin "cross" drawn in the center. The subject is in focus when you see "focused" both the cross and the aerial image passing through the transparent area, as if they were somewhat "superimposed" in space.

As you can guess, using cross-hair focusing glass is somewhat tricky and requires experience, but is the ultimate solution when everything else fails.

 

[David A. Goldfarb]

I don't know about this particular screen, but some macro screens also have scales for determining the exact magnification ratio.

 

[max_ebb]

Thanks for the responses. At least now I understand the reasoning for having a focus screen specifically for macro work. As far as low light issues, I haven't had any problems with that as of yet, but it's nice to know about the cross hair screen if I ever do have issues with low light focusing.