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UltravioletPhotography

Glass in the Path: Sensor Stacks and Adapted Lenses


colinbm

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I've been told this by Brian Caldwell before and it's nice to have such a clear confirmation of a case in which size really counts :)

 

Some of the performance variations of the same lens used with different cameras/modifications obviously relate to the remaining stack differences.

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Thanks Bjorn

Though I don't speak 'Theoretical Optical Physics', I thought it might be helpful for people who use film era lenses on m4/3 cameras to see the difference in performance.

Cheers

Col

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Col, thanks for the link.

Roger Cicala and his crew have performed a lot of excellent tests and observations on the Lens Rental site. It is always quite interesting to read his write-ups. We need this kind of of testing and observation.

 

The results of the filter stack testing is revealing for us UVIR shooters who have had the filter stack removed from the camera and replaced with "clear glass". Given that we use older lenses which were made for film cameras (mostly), are we seeing the best that our lenses can give - at least prior to adding an external filter? And I wonder if these test results indicate that an internal filter UV-filter conversion might not be the best thing for such lenses as the UV-Nikkor or other older lenses? Perhaps even the clear glass should be removed from UVIR conversions? Or a very thin piece of glass used instead? But maybe it would be a good idea to use an internal UV-filter or clear replacement glass for the nifty Coastal 60/4 ?

 

I'm going to shoot Brian a PM and ask him to comment.

 

EDIT: I needed to add a remark about the clear replacement glass in a conversion. In the first writing I omitted that.

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Checked my notes - Brian stated that the Coastal Optics 60/4 was designed for digital cameras in that the design accounted for 2mm of flat glass with an index of 1.522 in front of the image plane.
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Col,

Thanks for the excellent link.

Following on Andrea's comment, with the filter stack removed and not replaced, as I have, then do film lenses perhaps perform better than they would on an unmodified camera?

Given the introductory comments on adapters, as well as his earlier post on that topic from last fall, which of these effects is larger may be luck.

LensRentals is only 4 miles down the road, I thought I felt a disturbance in the Force last week.

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It would appear that the micro4/3 cameras, for UV photography, would benefit from having the 'filter stack' removed from in front of the sensor & more so as it is thick, when primarily using older manual film era lenses. The micro4/3 cameras, I think all use the contrast-detection autofocus (CDAF), that compacts use, & so don't need the 'filter stack' replaced with an equivalent clear stack. This is unlike the dSLR's that use the phase-detection autofocus (PDAF).

Col

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