Proxel Lens Corrector

Started Aug 28, 2006 | Discussions thread
KL Matt Veteran Member • Posts: 5,885
Re: Proxel Lens Corrector

Another problem with vignetting is that if it's really severe, you can actually run into dynamic range issues with the image that wouldn't otherwise be there if the lens didn't exhibit light fall off. For instance, brightening the corners/edges of an image with the horizon in the upper third of the image could theoretically blow out highlights that were otherwise correctly exposed with vignetting. Darkening the rest of the image can lose shadow detail. Then there is the additional noise you would get in the corners if you're already shooting ISO 1600 etc. Push the corners over a half stop, and they're going to look noticeably different noise-wise than the middle. Add to that a decrease in sharpness from corrected barrel distortion, and you've got some considerable image degradation from the corrections, but only locally - could wind up with funny results. Anyone have more experience with this? Are the things i've mentioned actually an issue in practice?

It seems the software is very good at correcting these problems, but I really doubt that you can get great images using a fisheye and defishing all the time as someone suggested. 6MP is not huge and the 10-17 is reportedly only good for sharpness, not fantastic. I think if you want optimal results there's no way around a rectilinier lens like the 12-24 - software manipulations are a lossy process by definition, and probably best for touch-ups, not drastic de-fishing. But again, I have no practical experience here - please correct me if I'm wrong!


Roland Karlsson wrote:

John Lai wrote:

Like colour, lens softness, vignetting, dynamic range optimisation
corrections, but I doubt it is possible as this will need
sophisticated measuring instruments.

Vignetting we have plans to add.

It is not so easy to do correct really. Measurements is not easy -
and you have to measure at lots of F-stops and focal lengths. And -
you have to find some way to get even illumination. Do vignetting
affect contrast?

I have not seen the CS2 vigneting fix. Is it good? The PTLens I
found hard to use. Normally I make a mask in Photoshop and then use
blending. That is also tedious - but the result is nice. Hmmmm ...

One problem is that you want to correct the vignetting and still
preserving the contrast and color.

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Take it easy,


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