Purple fringing and IR..

srichards

srichards

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I was wondering recently whether the visible purple fringing that you can see with some lenses and sensors is related to IR? My web cam that has no IR cut filter seems to give greys a certain purple tint which looks very like the fringing effect. It also seems to be the same shade that is chroma noise in high iso images. This may of course be a complete coincidence but it made me wonder.

To that end.. has anyone tried the combined Hoya uv and ir cut filters and noticed any reduction in either of these?

My sony 30mm is a b****r for the purple edges so I thought it would be an excellent candidate to experiment with.
 
Can't answer the uv/IR filters, but purple fringing has to do with the quality of the glass in the lens and the wavelength of light. When the lens is wide open, it has to bend the light from the edges of the lens. Glass bends light different amounts depending on frequency (which is why a prism creates a rainbow). The purple fringing is the fact that the blue light bends less (or is it more - I can't remember) and smears.
 
Panasonic also seem to know how to control it more than anyone else. I get virtually zero purpling with my old bridge camera so it beats me how sony and a lot of the others can't manage it with current lens and sensor tech.

The purpling effect is an absolute pet hate of mine. Drives me nuts!
 
srichards said:
Panasonic also seem to know how to control it more than anyone else. I get virtually zero purpling with my old bridge camera so it beats me how sony and a lot of the others can't manage it with current lens and sensor tech.

The purpling effect is an absolute pet hate of mine. Drives me nuts!
Click to expand...
Micro 4/3rds has CA correction built in. You may find that it is processed out of your bridge camera by knowing the lens characteristics at a given lens focal length and aperture. You may also find the issue is less apparent the smaller the sensor (and commensurately higher f numbers at a given effective focal length).

Lightroom is getting better at CA removal at every release....
 
arad85 said:
Micro 4/3rds has CA correction built in. You may find that it is processed out of your bridge camera by knowing the lens characteristics at a given lens focal length and aperture. You may also find the issue is less apparent the smaller the sensor (and commensurately higher f numbers at a given effective focal length).

Lightroom is getting better at CA removal at every release....
Click to expand...

Looks like photoshop CC has some kind of CA removal tool in it as well :thumbs:
 
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