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jdman · Joined: 13 May 2001 Posts: 302 Location: Midwest

Has anyone ever adjusted the focus on a model 22? Would you measure to the film plane? Thanks, Russ

Jim23 · Posted: Wed Mar 05, 2003 8:02 pm Post subject:

I placed a ground glass (actually a discarded Yashica focusing screen) on the film plane, and using a loupe, focused on a distant (appx. 2km) antenna tower (to approximate infinity). The focusing screen at the film plane indicates perfect focus as well as the ground glass on top. Thus, they match as well as the focusing knob is indicating infinity; however, there is a strange problem. At intermediate distances (for example 10 feet focusing on newsprint) the ground glass at the film plane and the finder still match nearly perfect focus. The problem is that the distance scale on the focusing knob lies (by about 2 feet!). Thus the lenses have very close match on their focal lengths, but they don't match what the scale on the knob says except at infinity. My guess is that the taking lens is not the advertised focal length, and it was matched with an equally-off viewing lens, so therefore the focusing scale is not correct. Is this possible?

Baker · Joined: 08 Apr 2002 Posts: 85 Location: Texas

glennfromwy · Joined: 29 Nov 2001 Posts: 903 Location: S.W. Wyoming

I have tested the focus on a great many old TLRs and others using the same method. My experience is that almost none of the focus scales correspond with ground glass focusing. It's not really a big deal as the lenses were made to be stopped down and depth of field will carry it. Hopefully, if using scale focus, you would be focused just ahead of the subject for this to work well.

_________________
Glenn

"Wyoming - Where everybody is somebody else's weirdo"