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08-20-2012, 09:55 AM   #16
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QuoteOriginally posted by D1N0 Quote
Great, a bunch of seventh day hood evangelists. Well sometimes a hood does'nt cure lens softness. Later Jupiter Nines with multi coating usually are sharp wide open. Do all lenses need to be coated or, just the front and back one?
I'm not a hood evangelist in particular - just trying to understand why/how a diopter can decrease haze (or contrast) from a lens. I think it worth the time to figure out why the diopter is having this effect - its coating? its hooding effect? its lens effect-(a good chance that the diopter is sending essentially parallel illumination into the Jupiter).

There may be something to that last thought, in effect the diopter acts as a much longer tube than it actually is regarding the non-parallelism of the light exiting it.

The effect of the diopter's coating might be separated from other effects by replacing the diopter with a good multicoated UV filter.

Generally all lenses need to have some coating at an interface with another material to avoid light loss and veiling or specular glare.

Dave in Iowa

08-20-2012, 10:29 AM   #17
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Well this is what i looks like



I may be an aperture effect, because of the broad metal ring. The cosina is only F3.5 and the Jupiter is F2. De Diopter takes about half a stop of the shuttertime. 1/180 without en 1/125 with diopter measured on an even white wall. This doesn't happen when I stop the lens down. So F2 might actually change to F2.5.
08-20-2012, 11:32 AM   #18
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QuoteOriginally posted by D1N0 Quote
Well this is what i looks like



I may be an aperture effect, because of the broad metal ring. The cosina is only F3.5 and the Jupiter is F2. De Diopter takes about half a stop of the shuttertime. 1/180 without en 1/125 with diopter measured on an even white wall. This doesn't happen when I stop the lens down. So F2 might actually change to F2.5.
It would be easy to find out by getting a ring that goes from the jupiter 9's filter diameter to a smaller size, like

49-37mm 49 37 step down ring | eBay
49-28mm 49 28 step down ring | eBay

These cost about $2 USD delivered in the US.

Or, if it is easy enough, just remove the glass from the diopter lens to see if the aperture effect remains.

It might be worth $2 if the wide open contrast of the lens is substantially improved!.
08-20-2012, 12:01 PM   #19
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QuoteOriginally posted by D1N0 Quote
Well sometimes a hood does'nt cure lens softness.
Well, DUH!.

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