Feature request - disable lens correction

[Markus Zuber]

Hi Joost

Is there a way for disabling lens correction and saving it in the standard preset. Processed TIFFs are corrected by C1 or others – and I am quite sure that many users do not realise that these images are corrected once again by default.

Thanks, Markus 

[PTGui Support]

Hi Markus,

The trick is to go to the Optimzer tab and switch to Advanced mode. Then
Align Images will no longer override its settings.

So in your template, switch to Advanced. Go to Optimizer, click on
Advanced. Then uncheck the a/b/c checkboxes.

Then do File - Save As Template and use this template for your projects.

Generally it doesn't hurt though to keep lens correction enabled.

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

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[Erik Krause]

Am 08.07.2024 um 23:06 schrieb 'PTGui Support' via PTGui Support:

> Generally it doesn't hurt though to keep lens correction enabled.

To elaborate a bit: PTGui doesn't use a standard correction like C1
does. Instead, it calculates the distortion from the control points in
the overlap region. Hence, there will be no double correction, only a
refinement of the correction C1 does.

For stitching, I personally don't like the corrections raw converters
do. They are an average of some lenses, in the best case. But lenses
have tolerances, and your actual lens might be slightly different. PTGui
tries to minimize the control point distance, its goal is to have the
least stitching errors.

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Erik Krause
http://www.erik-krause.de

[Markus Zuber]

Thanks - in most cases I did not see a problem. In some special cases however it looked like double correction was way over the top.
But good to know anyway. Maybe interesting to know: would you recommend not applying any lens correction in C1 when stitching?

Markus



Am 09.07.24, 17:36 schrieb "'Erik Krause' via PTGui Support" <pt...@googlegroups.com <mailto:pt...@googlegroups.com>>:

http://www.erik-krause.de <http://www.erik-krause.de>


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[Erik Krause]

Am 09.07.2024 um 17:48 schrieb Markus Zuber:

> In some special cases however it looked like double correction was
> way over the top.

PTGui looks at the control points and optimizes the parameters you
allowed on Optimizer tab to minimize control point distance. It might
for example mistake parallax errors for lens distortion (which can't be
determined from a few control points), in which case the images get
pretty distorted. But that has nothing to do with double correction.

To prevent that, you can use a perfectly adjusted panoramic tripod head
and eventually calibrate your (prime) lens. For this, you shoot a 360°
panorama with 50% overlap in a wide open space. Set a lot of control
points, but none on nearby objects or the floor. After optimization, you
should get correct lens parameters for your lens. Save those to the lens
database for later use.

> Maybe interesting to know: would you recommend not applying any lens
> correction in C1 when stitching?

It depends. I don't know the lens correction model of C1. It might
correct for other, more or less types of distortions than PTGui, which
can correct for the three parameters of a radial distortion polynomial
(a, b, c) and lens shift. a,b,c corrects for pincushion, barrel or
mustache distortion, lens shift for decentering the lens on the optical
axis.

The latter is not a property of the lens alone, but also depends on the
specific camera, hence can not be corrected by a C1 standard preset. So
if PTGui normally shows some values for lens shift (if you used "Heavy
and lens shift" or checked it in the advanced interface), it might be
better to not use C1 correction, since it will apply it with the wrong
center. For example.

[Markus Zuber]

Thanks!

Markus
web: https://www.markuszuber.com


Am 09.07.24, 18:34 schrieb "'Erik Krause' via PTGui Support" <pt...@googlegroups.com <mailto:pt...@googlegroups.com>>:

http://www.erik-krause.de <http://www.erik-krause.de>


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