I have a Rolleiflex T, model 1 (gray leather, with a decal inside stating for sale only in military exchanges in Europe), uses a 75mm Tessar. I bought it used about 3 years ago, had it overhauled, shutter checked, etc, and have been using it with great results. I remember using a 3.5f in the late 60's, and I'm thinking about moving up to something newer. I'm not having problems, but I know the Planar series is a better lens.
Some of my questions:
If I don't care about the lens speed, is the 2.8f worth the price difference? (seems like I've heard over the years that the 3.5f is sharper, can't remember).
Is either one noticeably better than the Tessar I have?
What is a good vintage, (for shooting, not collecting) that balances cost with quality and reliability? (seems like I've heard the 70's vintage are popular.)
Depending on how much the newer one would be, I would like to keep the one I have, as a backup. Is there anything special about it?