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07-16-2010, 02:59 PM   #46
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QuoteOriginally posted by Lowell Goudge Quote
While I do not dispute that longitudinal CA produces purple fringing in OOF zones in front if ideal focus, I believe there is a destinction between longitudinal CA and the "blooming" of purple surrounding subjects typically in strong backlit situations, that is attributed to sensor design
Thank you Lowell. I could not have said it better myself.

I am well acquainted with LoCA and have at least one lens that has it in spades (Zuiko 35/2 on my XA). I am also well acquainted with PF and remain confident that they are not the same.

Yes, the FA 77 has PF and no, it is not LoCA. As for other lenses that don't have PF, I don't dispute that at all. After all, it is pretty obviously lens specific and if your APO lens is not affected...good deal! I have several non-APO lenses including one cheap Russian that don't have it either.


Steve

07-16-2010, 03:26 PM   #47
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Steve

It just occurred to me that there may be a lens design component to PF that is truly independent of CA

Specifically with respect to the issue of vignetting on some lenses as a function of the angle light hits the sensor, and digital only lenses being designed to have the light strike the sensor more purpendicular to the sensor than was necessary on film. What if the same issue or some kind of optical design phenemon causes pf on a digital sensor but does nothing to film, perhaps internal reflection between the sensor and micro lens on the sensor refracting the light out to adjacent sensor cells?

Last edited by Lowell Goudge; 07-16-2010 at 03:49 PM.
07-16-2010, 07:44 PM   #48
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QuoteOriginally posted by Lowell Goudge Quote
Steve

It just occurred to me that there may be a lens design component to PF that is truly independent of CA

Specifically with respect to the issue of vignetting on some lenses as a function of the angle light hits the sensor, and digital only lenses being designed to have the light strike the sensor more purpendicular to the sensor than was necessary on film. What if the same issue or some kind of optical design phenemon causes pf on a digital sensor but does nothing to film, perhaps internal reflection between the sensor and micro lens on the sensor refracting the light out to adjacent sensor cells?
What you are suggesting is one of the theories I have read. Some have also suggested that it is caused by a subtle interaction between microlenses on the sensor and errant light from the lens rear element. Whatever the cause, I can guarantee you that the people who design digital cameras probably know more than they are telling. The issue of PF on digital cameras is almost as old as the technology itself but has become much less prominent with each generation of sensor. I wonder why?


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07-16-2010, 07:54 PM   #49
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QuoteOriginally posted by stevebrot Quote
What you are suggesting is one of the theories I have read. Some have also suggested that it is caused by a subtle interaction between microlenses on the sensor and errant light from the lens rear element. Whatever the cause, I can guarantee you that the people who design digital cameras probably know more than they are telling. The issue of PF on digital cameras is almost as old as the technology itself but has become much less prominent with each generation of sensor. I wonder why?


Steve
Probably for the same reason vignetting has gone away, sensor designers learned and moved forward. I thought about this , in fact in responding to someone asking about the advantages of designed for digital lenses, and thought these two threads were related

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