Purple flare: Causes and remedies

Started Mar 1, 2013 | Discussions thread
OP Anders W Forum Pro • Posts: 21,468
Re: Purple flare: Causes and remedies

Timur Born wrote:

Anders W wrote:

Timur Born wrote:

Shot as Jpg or Raw? Tone curves involved?

RAW. Processed in LR. No tone curves involved.

My fault. When was write "tone-curves" I mean anything from linear to non-linear (LR's exposure slider isn't linear anyway, is it?), so I wasn't far off with my suspicion that the increased noise meant digital gain.

What happens when something purple is in the scene and would that filter and necessary gain babe preferable to using LR's defringing instead?

If there would be something genuinely purple in the scene (i.e., a subject with purple color rather than flare in the optical path) it would be rendered purple even with the purple filter after proper WB was set. So the filter reduces the false purple that isn't really part of the scene but would leave genunine purple intact.

As to LR's defringe tool, it is not an ideal tool for removal of the false purple on several grounds: because LR doesn't see the flare as a fringe and therefore has limited effect and/or because its impact is to desaturate which replaces one artificial/undesirable hue by another.

Local change of WB (using LR's brush tool) is usually a better bet than the defringe tool in my experience. But the point here is that the filter counteracts the cause of the purple disease in the first place rather than attacks its symptoms afterwards. That said, I regrettably don't think that I have discovered some miraculous cure-all, nice as that would be, since heavy filtering has costs of its own (not least the loss of several stops worth of light). I am in fact more interested in the effect of the filter because of what it tells me about the cause of the purpleness than as a practical tool in the field.

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