John Hermanson wrote:
> I think this floating dot anomaly was brought up here a year or so ago,
> or I saw it on another list. A direct reflection off the low pass filter
> to the rear element and back.
>
It was indeed. However, I have also seen images posted with ghost lights
caused by filters on the front of a lens. The reflection off the sensor
assembly going through all the non-flat elements and reflecting back off
the flat filter to the sensor. Not likely with all lenses, or perhaps
even with the same zoom lens it may be dependent on focal length, but it
does happen.
That's the reason behind the new 'digital' filters, with more extensive
coatings. It's also behind the digital version of many lenses, like the
Tamron Di and Di II lenses - optical design changes to eliminate any
possible reflections and more extensive internal coatings.
Moose
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