It's a cold, gray morning about to rain here in Tennessee, and I'm not inclined to get out until the rain washes the salt off the roads which means I have too much time to think...
Bob Salomon has mentioned the Linhof and Sinar use a $500k Siemens star projector to test lenses, and I want one. Note that I did not say that I wanted to BUY one! Although when I Googled "Siemen's Star Projector" I did get a lot of hits to compare prices and write reviews for one.
So how does this thing work? I assume a lot of the high cost is producing an easy-to-use, rugged, high volume machine for Linhof and Sinar, so maybe I could make something that remotely resembles one. It seems to be something like projecting a pattern and looking for changes as the lens is rotated.
Questions:
How does this thing work in theory? It sounds sort of like an enlarger projecting a "resolution chart" with the lens to be tested used as a projector lens.
What's a "star"? Is it a 5-pointed thing like we're accustomed to, or is it something like a fine pattern of 3 or more intersecting lines, etc.
Are all the "stars" the same size or are there large ones and small ones? I assume they are very precisely cut as in laser cut?
What's the light source requirements?
Is there a "reference lens" that candidates are compared to, or do people just use their judgment about what's good enough?
So could I use an 8x10 enlarger head to project an image of a laser-cut pattern through a test lens mounted in a "lens chuck"?
Well, that should be enough to incite some comments.
Cheers, Steve
Bookmarks