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06-16-2012, 01:21 PM   #46
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Using a low dispersion glass combined with a high index Barium glass could have easily solved the CA problem Pentax had. However, it is my belief that DO was used instead, more as a space savings option to the bulkier traditional CA solution.

06-16-2012, 02:03 PM   #47
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QuoteOriginally posted by desertscape Quote
Using a low dispersion glass combined with a high index Barium glass could have easily solved the CA problem Pentax had. However, it is my belief that DO was used instead, more as a space savings option to the bulkier traditional CA solution.
...maybe they wanted something patentable...just a little jaded
06-19-2012, 12:52 PM   #48
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QuoteOriginally posted by Anvh Quote
As far as i know the system is sensative for light not colours, but yeah it might be more sensative for certain colours...
I think the point being made is that if CA occurs on the image seen by the AF sensor, the different wavelengths being split and appearing across a wider area would both confuse the AF sensor and make that area appear out of focus.
06-19-2012, 05:26 PM   #49
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QuoteOriginally posted by Ryan Trevisol Quote
I think the point being made is that if CA occurs on the image seen by the AF sensor, the different wavelengths being split and appearing across a wider area would both confuse the AF sensor and make that area appear out of focus.
I know and that wasnt the discusion.

06-21-2012, 01:01 PM   #50
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QuoteOriginally posted by Asha Quote
garyk, the Schmidt plate is an asphere, not a diffractive element. In the original design, the Schmidt corrector is mainly for spherical aberration in a spherical mirror (reflective telescope). A diffractive optical element is more along the lines of a Fresnel lens. It DOES have optical power, ie, it behaves much as a "normal" lens would, but with subtle differences. Plus, it can be made more flat and thus make for a more compact system.
Ok, thanks
Just looked it up.. Chromatic aberration is where different wavelengths focus at different points on the focal plane and spherical aberration is where the Focus is focused at different points on the focal plane. Looked at a diffractive optical element design also. I know squat about AF but i think I will look into it. I see where a DO element can reduce optical elements in the lens also. Interesting thread.

Last edited by garyk; 06-21-2012 at 01:41 PM.
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