Vignetting/Blending issues with PTGui v12 Beta

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Conrad Allan

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Jan 20, 2021, 5:44:13 AM1/20/21
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​Hey Joost,


As mentioned here, I'm having some issues removing the vignetting/blending in of my hdris.
I've attached 3 of the hdris at low res and you can see the issues as you flick through them.

A month or so ago I had another similar set of blue sky images which I was able to stitch nicely. The only main difference I can think of between the old set and the new one is that I'm now using a 6stop ND filter. There could be some other differences in the shoot procedure and settings though as it's been quite some time and I can't quite remember.

Anyway, if you're able to discover why the images aren't blending properly I would be interested in knowing and how to fix that!

I've sent access to the images through to the support email.
_DSC1365 Panorama_2k.jpg
_DSC1005 Panorama_2k.jpg
_DSC1185 Panorama_2k.jpg

PTGui Support

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Jan 21, 2021, 7:17:05 AM1/21/21
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Hi Conrad,

Next time please help me by not letting me download 150G of data in
order to see a problem!

The vignetting in your images is quite strong and I'd argue that PTGui
actually did quite a good job removing it. But in blue sky even very
minor brightness differences are quite noticeable.

If you switch to Unblended view, you can see that your images seem to
have some unequal brightness. See attached screenshot. I'm not sure why
this is, it could be the raw conversion or perhaps the camera shutter,
but I think this is responsible for the remaining issues. The blender
will do a good job smoothing out the brightness differences, but the eye
is very sensitive to gradients in the sky.

Disabling 'find optimized seams' might help, because PTGui will use
similar sized chunks from each image (preventing smaller sized 'hotspots').

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

On 20/01/2021 11:44, Conrad Allan wrote:
> ​Hey Joost,
>
>
> As mentioned here
> <https://groups.google.com/g/ptgui/c/Sbwt1U4Geso/m/PBwU3eqHCQAJ>, I'm
> having some issues removing the vignetting/blending in of my hdris.
> I've attached 3 of the hdris at low res and you can see the issues as
> you flick through them.
>
> A month or so ago I had another similar set of blue sky images which I
> /*was */able to stitch nicely. The only main difference I can think of
> between the old set and the new one is that I'm now using a 6stop ND
> filter. There could be some other differences in the shoot procedure and
> settings though as it's been quite some time and I can't quite remember.
>
> Anyway, if you're able to discover why the images aren't blending
> properly I would be interested in knowing and how to fix that!
> *
> *
> *I've sent access to the images through to the support email.*
>
> --
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Screenshot 2021-01-21 at 13.00.27.png

Conrad Allan

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Jan 21, 2021, 8:55:59 PM1/21/21
to PTGui Support
Oh god, sorry about that! I work with TB's of data every day so I don't have a 'normal' perspective of what is a lot of data.

Thanks for testing. With the unequal brightness, when I look at the RAWs in Lightroom they all have a consistent exposure set.

Can you shed a little light for me on how PTGui determines overall brightness of an image? From my investigation I'm thinking PTGui uses shutter speed to determine brightness and maybe also ISO, but ignores Aperture.
Is this correct? 

This would then explain the calculated brightness variation in PTGui as these latest images were shot with inconsistent Shutter Speed and ISO but a locked aperture whereas I have another set which was shot at fixed shutter speeds and ISO but with varying Aperture.


Thanks!

PTGui Support

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Jan 22, 2021, 3:24:18 AM1/22/21
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Now that I look again the problem is pretty obvious, it seems you
bracketed in AV mode? For example the -1 blend plane varies between 1/25
and 1/30 s.

PTGui calculates the EV from ISO, aperture and exposure time together.

It will actually compensate for the differences in exposure but this is
probably not entirely perfect and your eye is very sensitive to
brightness differences in the sky.

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

> www.ptgui.com <http://www.ptgui.com>
> <https://groups.google.com/d/msgid/ptgui/d97ac404-37eb-477b-8827-05a305baacd0n%40googlegroups.com?utm_medium=email&utm_source=footer
> <https://groups.google.com/d/msgid/ptgui/d97ac404-37eb-477b-8827-05a305baacd0n%40googlegroups.com?utm_medium=email&utm_source=footer>>.
>
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singlebp.pts

Conrad Allan

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Jan 25, 2021, 11:44:22 PM1/25/21
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Hey Joost,

Thanks for the info and sorry about the delay, I was hoping to have a more solid response and questions for you after doing some more research test shoots but it's been too cloudy.

While I do some of that testing, can you tell me what you suggest is the best setting for exposure metering? The options being:
- Matrix metering
- Center-Weighted metering
- Spot metering
- Highlight-weighted metering

Also, what about Vignette Control? I'm using a Nikon Z7 and it has High|Normal|Low|Off..

Choosing how to set these options confuses the hell out of me when it comes to Ptgui because of how particular the process can be. If there's any documentation that I've missed which covers this I'd appreciate knowing about it!

Thanks,



Conrad W. Allan

Head Of Product, MattePaint Co-founder 

MattePaint Pty Ltd

Phone: +61480193024

Email: con...@mattepaint.com

My Timezone is AEST, Brisbane.



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PTGui Support

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Jan 26, 2021, 3:40:40 AM1/26/21
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Hi Conrad,

It's best to shoot in M mode. This means that all camera metering will
be disabled.

You need to pick a suitable exposure time and aperture. One way to do
this is by pointing the camera at a dark part and at a bright part of
the scene, read the values in automatic exposure mode and then set your
M mode bracketing around the average of these two.

If the camera can remove the vignetting perfectly, you can enable
in-camera vignetting correction. If it's not perfect, then disable it
entirely and let PTGui correct the vignetting. Shoot a test panorama to
find out.

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

On 26/01/2021 05:43, Conrad Allan wrote:
> Hey Joost,
>
> Thanks for the info and sorry about the delay, I was hoping to have a
> more solid response and questions for you after doing some more research
> test shoots but it's been too cloudy.
>
> While I do some of that testing, can you tell me what you suggest is the
> best setting for exposure metering? The options being:
> - Matrix metering
> - Center-Weighted metering
> - Spot metering
> - Highlight-weighted metering
>
> Also, what about Vignette Control? I'm using a Nikon Z7 and it has
> High|Normal|Low|Off..
>
> Choosing how to set these options confuses the hell out of me when it
> comes to Ptgui because of how particular the process can be. If there's
> any documentation that I've missed which covers this I'd appreciate
> knowing about it!
>
> Thanks,
>
>
>
> *Conrad W. Allan*
>
> Head Of Product, MattePaint __Co-founder
>
> MattePaint Pty Ltd__
>
> Phone: +61480193024
>
> Email: con...@mattepaint.com <mailto:con...@mattepaint.com>
>
> My Timezone is AEST, Brisbane.
>
>
>
> On Fri, 22 Jan 2021 at 18:24, 'PTGui Support' via PTGui Support
> <pt...@googlegroups.com <mailto:pt...@googlegroups.com>> wrote:
>
> Now that I look again the problem is pretty obvious, it seems you
> bracketed in AV mode? For example the -1 blend plane varies between
> 1/25
> and 1/30 s.
>
> PTGui calculates the EV from ISO, aperture and exposure time together.
>
> It will actually compensate for the differences in exposure but this is
> probably not entirely perfect and your eye is very sensitive to
> brightness differences in the sky.
>
> Kind regards,
>
> Joost Nieuwenhuijse
> www.ptgui.com <http://www.ptgui.com>
> > www.ptgui.com <http://www.ptgui.com> <http://www.ptgui.com
> <mailto:ptgui%2Bun...@googlegroups.com>
> >      > <mailto:ptgui+un...@googlegroups.com
> <mailto:ptgui%2Bun...@googlegroups.com>>.
> <mailto:ptgui%2Bunsu...@googlegroups.com>
> > <mailto:ptgui+un...@googlegroups.com
> <mailto:ptgui%2Bunsu...@googlegroups.com>>.
> <https://groups.google.com/d/msgid/ptgui/9e5dff21-8a66-476b-916f-13be86c652a7n%40googlegroups.com?utm_medium=email&utm_source=footer
> <https://groups.google.com/d/msgid/ptgui/9e5dff21-8a66-476b-916f-13be86c652a7n%40googlegroups.com?utm_medium=email&utm_source=footer>>.
>
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Conrad Allan

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Feb 5, 2021, 1:25:11 AM2/5/21
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Hi Joost,

I was able to largely improve the quality by totally removing all vignette correction from the camera. This makes sense since the internal vignette correction is probably quite generic. Better to let PTGui handle it.
I haven't had a chance to take another series on a pure blue sky as it's been cloudy, but I suspect it'll be fine.


Thanks again!



Conrad W. Allan

Head Of Product, MattePaint Co-founder 

MattePaint Pty Ltd

Phone: +61480193024

My Timezone is AEST, Brisbane.

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