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Isco Ultra-Star f-number


seanc
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I don't know why it has been so difficult to find an answer to this... maybe I just can't find the right combination of search words.

1) What is the f= number etched into the lens housing?  I've seen f=65mm, 2.65in... or f=75mm, 2.95in.  What is that f= number referring to?

2) Does a larger number equate to a larger rear opening, and a small number equate to a smaller rear opening?

3) Does the number also determine a larger or smaller size for the front opening?

Seems an important bit of information to have when trying to determine what size taking lenses I'll be able to use.  Without an Isco in hand, just looking at photos and descriptions on Ebay, it's been impossible to figure out the sizes of different parts of the lens to know what I'll be working with and how other parts of the setup will match up.

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EOSHD Pro Color 5 for Sony cameras EOSHD Z LOG for Nikon CamerasEOSHD C-LOG and Film Profiles for All Canon DSLRs

I have always wondered if the shorter focal length ones can take wider lenses. Mine says 75mm and I have a special 75mm lens that gets so close to the adapter that it doesnt vignette.

No, all the anamorphic lens part are the same.  The focus length is just for different size of screen or movie theater use.

 

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