Public bug reported:
The horizontal field of view (HFOV) property of a picture is critical to
allow proper stitching. Inadequate values forbid automatic detection of
control points, which is a central piece (and major added value) in
Hugin's, and hence breaks the automated stitching workflow. Thankfully,
Hugin automatically computes the HFOV value for pictures with valid EXIF
data. Again, this is a great benefit which avoids manual computation for
each lense and lengthy entry of manual data.
In traditional cameras, the HFOV is mainly a function of the lense's
focal length: adjusting the zoom between two shots with the same camera
results in different focal lengths for each shot. This information is
correctly read and interpreted into distinct HFOV by Hugin. In contrast,
modern digital cameras, such as samsung cell phones to cite just one
widely-spread example, typically feature fixed lenses with a unique
focal length. Yet, it is still possible to take shots with different
zoom factors (or, say, to be given pictures to stitch that were taken
with such a device and with different zoom factors...). In this case,
the focal length information is identical for all shots and the zoom
information is encoded in a distinct EXIF tag, called the 'Digital Zoom
Ratio'. Currently, it seems that Hugin doesn't take advantage of this
tag, hence wrongly assuming that all pictures taken with the same
'digital camera' have an identical HFOV. This causes Hugin to be unable
to stitch the pictures, because it typically fails to find control
points.
This might be relatively straightforward to fix given that:
- The digital zoom ratio affects the HFOV in a simple manner, so it should be
possible to compute the HFOV by taking into account both the lense's focal
length and the digital zoom ratio (when available)
- Hugin seems to rely on Exiv2 to acquire EXIF data from files, which
supports the 'Digital Zoom Ratio' tag, so it should be possible to access this
tag with the existing infrastructure. I checked that the command `exiv2 -pt
image.jpg` on my images return the tag `Exif.Photo.DigitalZoomRatio` with the
correct value. The same values are also read by Exiftool (checked with command
`exiftool image.jpg`).
I'm using Hugin 2021.0.0.52df0f76c700 (built with Exiv2 0.27.5) on
Ubuntu 22.04.1. The version of Exiv2 that I used in the command line is
also 0.27.5.
** Affects: hugin
Importance: Undecided
Status: New
--
You received this bug notification because you are a member of Hugin
Developers, which is subscribed to Hugin.
https://bugs.launchpad.net/bugs/219
Title:
Take into account digital zoom ratio EXIF tag in the computation of
the HFOV
Status in Hugin:
New
Bug description:
The horizontal field of view (HFOV) property of a picture is critical
to allow proper stitching. Inadequate values forbid automatic
detection of control points, which is a central piece (and major added
value) in Hugin's, and hence breaks the automated stitching workflow.
Thankfully, Hugin automatically computes the HFOV value for pictures
with valid EXIF data. Again, this is a great benefit which avoids
manual computation for each lense and lengthy entry of manual data.
In traditional cameras, the HFOV is mainly a function of the lense's
focal length: adjusting the zoom between two shots with the same
camera results in different focal lengths for each shot. This
information is correctly read and interpreted into distinct HFOV by
Hugin. In contrast, modern digital cameras, such as samsung cell
phones to cite just one widely-spread example, typically feature fixed
lenses with a unique focal length. Yet, it is still possible to take
shots with different zoom factors (or, say, to be given pictures to
stitch that were taken with such a device and with different zoom
factors...). In this case, the focal length information is identical
for all shots and the zoom information is encoded in a distinct EXIF
tag, called the 'Digital Zoom Ratio'. Currently, it seems that Hugin
doesn't take advantage of this tag, hence wrongly assuming that all
pictures taken with the same 'digital camera' have an identical HFOV.
This causes Hugin to be unable to stitch the pictures, because it
typically fails to find control points.
This might be relatively straightforward to fix given that:
- The digital zoom ratio affects the HFOV in a simple manner, so it should
be possible to compute the HFOV by taking into account both the lense's focal
length and the digital zoom ratio (when available)
- Hugin seems to rely on Exiv2 to acquire EXIF data from files, which
supports the 'Digital Zoom Ratio' tag, so it should be possible to access this
tag with the existing infrastructure. I checked that the command `exiv2 -pt
image.jpg` on my images return the tag `Exif.Photo.DigitalZoomRatio` with the
correct value. The same values are also read by Exiftool (checked with command
`exiftool image.j
