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View Full Version : Kenro K 8.25" f/6.8



jss
6-Jan-2011, 09:39
I have the Kenro K, 8.25" f/6.8 dagor but I can't seem to find hard stats about it. Does anybody know the image circle?

John Kasaian
6-Jan-2011, 09:43
Turn the lights out and point it out the window while projecting against a blank white wall will give you an idea.

Fotoguy20d
6-Jan-2011, 09:47
I have the same lens in a barrel. The lens elements will interchange with those of a 8.25" Goerz Dagor in dial set compur that I also own. You should find coverage to match that of a Dagor - 210mm can cover 8x10 when stopped down far enough.

Dan

jss
6-Jan-2011, 10:10
Is this a legit method of determining if a lens covers at a given aperture: Stop down to say f/22 then look through the open back of the camera from each corner. If I can see the entire aperture (meaning the shape formed by the blades) then it will cover evenly.

Dan Fromm
6-Jan-2011, 11:43
Is this a legit method of determining if a lens covers at a given aperture: Stop down to say f/22 then look through the open back of the camera from each corner. If I can see the entire aperture (meaning the shape formed by the blades) then it will cover evenly.Eh? What? All that test guarantees is that there will be no mechanical vignetting. It says nothing about the dread cos(theta)^4 fall off.

And that a lens puts light in the corners doesn't guarantee that it will put usable image there. What usable image means depends on how the final print is to be made; enlarging requires better quality in the negative than enlarging does.

This is why we have so many wrangles about Dagors' coverage. Different interpretations of "covers."

So, jss, you'll get conflicting answers, all correct, to what you thought was a simple straightforward question. If you want to know what your lens will do for you, ask it, not us. Ask the question by shooting and looking closely at the negs. You'll understand the answer it gives you.

jss
6-Jan-2011, 13:35
super. thanks for the information everybody. i will shoot a couple tests and find out.

Dan Fromm
6-Jan-2011, 13:54
sorry, bad stupid typo. Replace the second enlarging with contact printing.