On 11/3/2016 9:15 PM, Mark Roberts wrote:
Collin B wrote:
At work I got the FA50/2.8 macro to have something AF for working in the
darker warehouse area.
But what I've seen, and it's not just a Pentax situation, when using it with
the florescent lights for piece shots I get this blue dot in the middle of
the image. Have yet to work with light placement to see if I can eliminate
it. But from what I've been reading it has to do with multiple factors, one
of which is the nature of the film coatings and the light
interactions/reflections with the sensor surface.
I only see the situation under the fl product lights.
Anyone else here have similar issues when product shooting? If so, how did
you resolve the situation?
It sounds like you've accurately assessed the cause of your
phenomenon. The first thing I'd do about it – the first thing I'd do
even if I weren't having that problem – would be to ditch the
fluorescent lighting. It's the most awful form of lighting you can
use. Not just because of the color balance but because it's not a
continuous spectrum source like incandescent lighting.
I've had the same thing happen with the A100mm f/2.8 macro. The hot
spotting is sensor reflections off an inside element. I found it is
really only a problem with high key backgrounds. It's related to veiling
flare.
I use studio strobes, not continuous lighting, so while the florescent
may be ugly light, they aren't causing this problem.
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