How best to deal with blurred edges caused by fisheye lens

[twalp]

I'm using a shaved Nikkor 10.5mm fisheye with a D800. I shoot "4 around".

I often notice a distinct border at blend points in the nadir of equirectangular images, where one side is sharp and the other blurred. Here's an example.

The Detail Viewer shows red lines corresponding to these borders between blurred and not. 

I assume what's going on is that PTG is using a distorted and therefore blurred area along the edge of the fisheye image, covering up part of the adjacent image that's quite sharp.

I'm wondering what the pros here do to avoid having these blurred areas have precedence over a sharper image beneath?  

Mask in green the sharp area at the bottom of each image?  Mask out the blurred areas near the edges of the bottom of each image? Crop out the blurred edges of the fisheye? Or what?

Thanks!

[Erik Krause]

Am 13.03.2016 um 21:57 schrieb twalp:
> I assume what's going on is that PTG is using a distorted and therefore blurred
> area along the edge of the fisheye image, covering up part of the adjacent image
> that's quite sharp.

PTGui tries to put the seam line as far away from the image borders as
possible. Moreover the blender favors the central parts of an image. At
least in theory. In practice it sometimes includes outer parts of
images, which often are blurred.

> I'm wondering what the pros here do to avoid having these blurred areas have
> precedence over a sharper image beneath?

If it's as obvious as in your shots, I mask the blurred image red. I
don't use green masks much, since they don't work for the alternative
blenders which I frequently use. Furthermore I use circular crop for my
full frame fisheye images, which cuts off the blurred corners. This only
works if the images get loaded in landscape orientation, which should be
the case if the orientation sensor in camera is turned off as
recommended. PTGui initializes the crop circle such, that it touches the
shorter edges and extends beyond the longer edges of the image.

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

[twalp]

Thank you for replying, Erik.  First, does this image qualify as a "full-frame fisheye image"? (I thought full-frame means the image is a complete circle without clipped sides like mine)

Does the red circle in the accompany picture illustrate what you mean by cropping off the blurred corners?

I believe I enabled my D800's "orientation sensor" because they were ending up upside down in PTGui. To compensate I tried entering a -90 for Roll (Image Parms) but commands like "Initialize and Optimize" would delete those changes, plus entering -90 in a bunch of bracketed shots was time consuming. So I've been liking having it enabled. Are you saying that cropping to remove the blurred area will not work unless the images are in landscape orientation, and if so, can you explain why (in layman's terms)?

[Erik Krause]

Am 14.03.2016 um 00:09 schrieb twalp:
> First, does this image
> <https://lh3.googleusercontent.com/Wi7Gz3q8BT2R41mkAFCwy9YfCuwQOoR_unmJKkJ2DPbLC1DLnXyMRyeayMztrLdG02M765ybiF_CVblussCkTFg6X-b5QFPbaSXnQ-gJEhACnXPwOAAnVgQhJEQBSKo4egZn4pdDim9pztVYUS9fjc0CQXKuWVv0bGCrXsUsNmN9mpq6BiszgvM7t-s89sHg_jxDlwMq8guPsAP_LYDJ7K0mUfofQ7bI_bOmmMuLsuaBwwFbLM-kAQaDABejGhY_M4lc54XIdZ8yY6Wy-NyImuw63qSQuZnSoElAMK2Vd44G4z_rWtbr03pW7vrzpKjLwMy5tDaMvyAH04TLC7xJ03V6dS10aauUKs0Z6tA6CIhBuaJ35Mj8exIa_gYJTk3EkI3HngM_rfK5uo8PFGw5mhqOW2vVMs3zSXb8U0dB3oEjbaABydNzwRTUYo_37auINPM8N-aHHJFeOPDZHjbQw7w6SOCQWwSRx0AnL7c1iYW5Ho-DDffxFd7EiuupWzJJzg3QBFoD_utZTqTIjjWgdo6gAf-LHV-0IsuJAS8BVYZb58HJaIfV1ziaIHHXGZMngoig9A=w270-h359-no>

...shows a forbidden sign only...

> qualify as a "/full-frame/ fisheye image"? (I thought/full-frame/ means the

> image is a complete circle without clipped sides like mine)

full frame fisheye means the image covers the full frame with no black
areas. Compare
http://wiki.panotools.org/Fisheyes#Types_of_Fisheye_Images

> I believe I enabled my D800's "orientation sensor" because they were ending up
> upside down in PTGui. To compensate I tried entering a -90 for Roll (Image
> Parms) but commands like "Initialize and Optimize" would delete those changes,
> plus entering -90 in a bunch of bracketed shots was time consuming. So I've been
> liking having it enabled.

This is not good, since the orientation sensor gives arbitrary results
if pointed straight up or down, in which case the images would not be
rotated correctly. Since PTGui applies lens correction relative to the
horizontal field of view, this would give strange results. Even if the
image is rotated 180°, which would look the same, the lens shift would
be applied the wrong way.
See http://www.ptgui.com/support.html#2_7 and other sections in the FAQ
(serach for "orientation")

You can rotate the panorama as total in 90° increments (together with
all source images), if you push the rotate button on Project Assistant
tab. If you shoot most of your panoramas always the same way, press
"Make Default" once you have good settings all together. PTGui will
start the next time applying all those settings from start. See
http://www.ptgui.com/support.html#5_10

> Are you saying that cropping to remove the blurred
> area will not work unless the images are in landscape orientation, and if so,
> can you explain why (in layman's terms)?

PTGui doesn't use the focal length internally, but the horizontal field
of view (hFoV). If you specify "Circular Fisheye" for your lens, PTGui
assumes a crop circle that matches the hFoV, which would be the image
width for portrait oriented images. The images can be shot in portrait
orientation nevertheless. If the camera orientation sensor is off,
they'll usually be treated as landscape.

[John Houghton]

On Sunday, March 13, 2016 at 11:09:52 PM UTC, twalp wrote:

Are you saying that cropping to remove the blurred area will not work unless the images are in landscape orientation, and if so, can you explain why (in layman's terms)?

Cropping can be used regardless of whether the image is in portrait or landscape orientation.  You need to specify the lens type as Circular Fisheye, even if the images i actually fullframe (no black areas).  You can then set the circle diameter as you please to crop away the corners of the image.  Of course you can use masking to exclude unsharp areas to achieve the same effect, in which case you can mask different sides of the image differently, if the blurring is not symmetrical.

Like Erik says, it's safest to switch off the camera's auto orientation feature to avoid problems when taking nadir and zenith shots with the camera pointing vertically up or down.  If you shoot raw,  it is only one click to rotate all the shots to portrait in the raw converter.  Alternatively, you can rotate all the images immediately after loading by using the rotate button on the Project Assistant tab. Or yet again, you can build this rotation into a template if stitching many panoramas shot in the same configuration.  Or you can select all the roll parameter boxes on the Image Parameters tab, and apply +/-90 there!

John