Vignetting Curve Invalid File Format Error

[Michael King]

I'm using PTGui Pro Ver 13.9 on Mac. 

For nightscape image stitching, I want to allow for lens vignetting of my raw files (I'd prefer not to export tiffs from Lightroom with vignetting correction if possible). 

The optimise auto function reports it cannot gather sufficient data, even when I manually add control points. So I' like to use the vignetting curve option. 

Can you tell me the precise file format I must use to avoid the 'File format error' message please? I've been unable to find the specification. I think I have the parameters okay, it's how to present them to PTGui that I can't find. 

Many thanks.

Michael

[PTGui Support]

Hi Michael,

It's only intended for saving and loading vignetting curves in PTGui,
the curve format is not compatible with other applications.

You can save a .ptgvignetting curve from PTGui, it will look like this:

vignettingcurve V1
-2.23728060722351074 1.9942706823348999 -7.11921975016593933e-2
1.58315703272819519e-1 -1.44996210932731628e-1

This is a 5th order polynomial.

You could try this: take two 50% overlapping images using your lens, at
daytime, at the same aperture as you are using at nighttime. If the
center of one image overlaps with the edge of the other, PTGui can
perfectly determine the vignetting curve.

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

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