Ptgui HDR bracketing vs EXIF

[cgiout]

Is it possible to know how Ptgui recognizes HDR brackets? I am trying to assemble a pano where there are n bracketa of 5 exposures (2ev5) and one of 15 exposures representing the sun (I have modified with exiftool the shutter speed inside the EXIF in such a way as to have expositions ranging from 1 / 30 up to 1/4000000000). When I tell Ptgui to enable the HDR function it automatically recognizes all the 5 brackets while the 15 one is divided into 3 brackets of 5 exposures.

If I try to link the 15 exposures not as HDR, it seems to work but ultimately the produced hdri pano is underexposed. Nothing serious however because i can raise up the exposure to gain again a correctly exposed image but i'm not really sure that linking images in such way is the correct approach.

I also tried to change shutter speeds into image properties unless changing them into exif but inside ptgui but it still breacks the 15 stops brackets into 3 and trying intead to link them it creates weird results (around the sun).

I am importing TIFFs inside PtGUI. If instead of letting PtGUI assemble the brackets I import the EXRs that i have merged before from the TIFFs, the final result is a correctly exposed image.

Any advice?

[PTGui Support]

Automatic linking of images will only work if all images have the same
bracketing sequence. You can always link manually by selecting groups of
images, right click, Link Selected Images.

In your case the easiest solution would be to load the 5-bracketed
images only, enable automatic linking, then add the 15 bracket exposure
and link those 15 images manually. Automatic linking is not going to
work when you load all images at once.

In PTGui Pro 12, for HDR images must always be linked.

Be careful about modifying the EXIF data, PTGui needs the correct data
for assembling HDR.

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

> --
> You received this message because you are subscribed to the Google
> Groups "PTGui Support" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to ptgui+un...@googlegroups.com
> <mailto:ptgui+un...@googlegroups.com>.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/ptgui/979b8a4d-2b8b-4e33-a3b9-331cf603f2d5n%40googlegroups.com
> <https://groups.google.com/d/msgid/ptgui/979b8a4d-2b8b-4e33-a3b9-331cf603f2d5n%40googlegroups.com?utm_medium=email&utm_source=footer>.

[cgiout]

Ok and thank you for your answer. 

My question now is: is it possibile to avoid EXIF changes and make the 15 stops exposures as 1 bracket directly into PtGui by changing image properties?

And why Ptgui creates an underexposed hdri pano? the 5 exp brackets has mid shutter speed 1/500, so why if i pre merge brackets to EXR and then i merge them into PtGui i obtain a well exposed HDRI, and by the use of PtGui merging not?

[PTGui Support]

On 27/05/2021 12:19, cgiout wrote:
> Ok and thank you for your answer.
> My question now is: is it possibile to avoid EXIF changes and make the
> 15 stops exposures as 1 bracket directly into PtGui by changing image
> properties?

Yes, just load your 15 images, select them in the Source Images tab,

right click, Link Selected Images.

> And why Ptgui creates an underexposed hdri pano? the 5 exp brackets has
> mid shutter speed 1/500, so why if i pre merge brackets to EXR and then
> i merge them into PtGui i obtain a well exposed HDRI, and by the use of
> PtGui merging not?

PTGui takes the middle exposure as a reference, i.e. the average of the
darkest and brightest exposure. If you are adding more underexposed
images, the average will be darker.

But there's no such thing as an underexposed HDRI, it's floating point
data after all.

Joost

[cgiout]

>Yes, just load your 15 images, select them in the Source Images tab,

>right click, Link Selected Images.

Probably you misunderstood my question. I know that i have to link them but my question was related to the image parameters. 

I mean, without changing the EXIF insiede every single TIFF, what are the values to change on order to make Ptgui merge correctly the exposures? 

Starting from the shutter speed 1/15000 all the other exposures have been modified by 2ev increase. Originally the 10 exposures were divided in 2 brackets of 5 images each at 2ev.

If i leave the TIFF as they are the merged bracket has halos around the sun. 

If i change the EXIF the merged bracket is correct. 

If i don't want to change the EXIF?ù

Thanks

[PTGui Support]

On 27/05/2021 14:07, cgiout wrote:
> Probably you misunderstood my question. I know that i have to link them
> but my question was related to the image parameters.
> I mean, without changing the EXIF insiede every single TIFF, what are
> the values to change on order to make Ptgui merge correctly the exposures?

I think I'm misunderstanding you indeed. But the exif data should match
the actual shutter speeds, aperture and ISO that you used. So you
shouldn't change anything.

If you used an ND filter, you can compensate for this by adjusting the
ISO column in Image Parameters.

Joost

[cgiout]

Ok, infact i'm using a ND filter. So you answered now: i have to change the ISO parameter.

Thank you