HDR bracket stichting vs ND Filters

[cgiout]

Hi all. I'm a photog specialized in 360x180 HDRI spheres.

In my workflow i often use ND filters in order to capture the complete EV range especially in sunny days and clear sky.

So i.e. i shoot a 2ev5 bracket set with ND filter and another 2ev5 without, for every angle.

I merge them into TIFF32 and then load into PtGUI. Simple workflow but time expensive with many brackets/angles.

Now the point. 

PtGUI automatically recognizes bracket sets stacking brackets by shutter speed. In the case above it would create 2 stacks per angle. One made of 2ev5 with ND and one 2ev5 without, because shutter speeds are exactly the same.

But trying to align all of these stacks produce weird results with global exposure. 

In order to make PtGUI recognize automatically the 2ev5 + 2ev5 as a single stack, i should edit the shutter speed of ND shots to the equivalent values (i.e. 1/8000 corresponds to 1/8388608 with ND1000 filter and so on) but it's slooow process, so, what i'm asking here is if exists a function in PtGUI that would batch that process.

Instead a conversion table into PtGUI for each type of ND filter (1000, 64, 16 and so on) would be great for this kind of purpose.

Any help appreciated.

Raf 

[PTGui Support]

Hi Raf,

What you could do is adjust the ISO of the ND images. Suppose all images
were taken at ISO 100. If your ND filter darkens by a factor 1000, the
equivalent ISO would be 0.1.

You can select multiple ISO cells in the image parameters tab
(Ctrl+click or Shift+drag) and enter the modified ISO value in 1 go.

Ensure that all images have an ISO value, then PTGui will use it to
calculate the effective EV.

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

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[cgiout]

Ok, thank you for your support.

I triedthe ISO trick for ND brackets but PtGUI now tells me that multiple lens were used and it doesn't auto recognise bracket sets.

Trying to align brackets (i coverted raw to jpg to save space) it complete the job and the HDR pano is good except for some aligning mismatches with the sun position. 

The fact that PtGUI doesn't create stacks of 10 exposures makes really impossible trying to add control points.

In this case i shooted a pano using a 16mm focal (i usualy use a 12mm fisheye) with 10 exposures per angle, for a total of 245 images.

[Erik Krause]

Am 09.09.2018 um 17:36 schrieb cgiout:
> I triedthe ISO trick for ND brackets but PtGUI now tells me that multiple
> lens were used and it doesn't auto recognise bracket sets.

Did you use a zoom lens? In this case you might have zoomed it while
changing filters which would cause a different focal lenght to be
recorded in EXIF. This should of course not happen if you want to merge
them later. However, it should be possible to assign a second lens type
to those images in PTGui, in which case you'd probably need to link the
bracketed sets manually.

You should investigate whether it's possible to work without changing
filters. 1/8000s f/22 to 1s f/2.8 is already 19 EV, plus the camera's
native DR of 8EV to 10EV, which would give you a total of 27EV to 29EV.
This should suffice.

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

[cgiout]

Hi, thank you very much for your advice. 

Infact PtGUI found 2 profiles, one 16mm and another 17mm. The weird thing is that i didn't shooted at 17mm, i checked if there were some shots at 17mm. Didn't find them.

Btw i'll take into account your advices.

Thanks all.

Raf

[John Houghton]

On Sunday, September 9, 2018 at 5:52:10 PM UTC+1, cgiout wrote:

Hi, thank you very much for your advice. 

Infact PtGUI found 2 profiles, one 16mm and another 17mm. The weird thing is that i didn't shooted at 17mm, i checked if there were some shots at 17mm. Didn't find them.

 PTGui is more concerned with the angle of view of the lens, which can vary according to the focus setting.  Is it possible that two focus distance settings were used (accidentally or on purpose), rather than two focal length settings?

John

[cgiout]

At first i was thinking at focal lenght, but may PtGui translate a variance in focus distance as a difference in focal lenght?

[PTGui Support]

Hi Raf,

It might be 17mm after optimization. And this may be caused by having
some images post processed in (e.g.) photoshop and the other images
straight from camera. If Photoshop alters the EXIF data, PTGui may
consider them 2 different lenses and create two lens profiles. You can
fix this by simply removing the second lens profile in the Lens Settings
tab (before running Align Images).

Secondly you said you have 10 shots per bracketed but a total of 245
images. This doesn't match. PTGui needs a strictly repeating sequence.

You can manually link images if needed: select multiple subsequent
images in the Image Parameters tab, right click and link the images from
the context menu.

If you need more help please post some images and the project file.

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

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[PTGui Support]

No it does not, PTGui doesn't read focus distance in the exif.
If you post two images which PTGui thinks are different lenses I can
look. Otherwise we can only guess what's happening.

Joost

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