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Author Topic: Taking fisheye to the extreme  (Read 15727 times)

bigben

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Taking fisheye to the extreme
« on: January 20, 2015, 04:08:58 AM »
Excited by my latest quick test of a combination I should have tried at the start.  Here's a teaser.
https://skfb.ly/CDWo

Shooting a more complete test this afternoon.

[update]Adding more samples here for those seeing this topic for the first time:

Test 1: repeated with optimised lens parameters
https://skfb.ly/CLRQ

Test 2: https://skfb.ly/CPpn
Entire building and surrounds
Full point cloud of this test: http://files.digitisation.unimelb.edu.au/potree/pointclouds/gatehouse_8mm.html
« Last Edit: February 08, 2015, 02:55:42 PM by bigben »

bigben

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Re: Taking fisheye to the extreme
« Reply #1 on: January 22, 2015, 12:56:52 AM »
As a panoramic photographer I work a lot with fisheye lenses.  I always had an idea to try a circular fisheye and now I don't know why I waited so long.  The first scene was just a quick series of 21MP  images shot while walking along taking a shot every metre or so... at arm's length from the building, camera pointing forwards.

This screengrab is the sparse cloud of the reshoot later that afternoon.  A previous test with a 24mm lens is here: https://skfb.ly/ArE9  Note the hole in the verandah. I took a short step ladder to get my hand above the flat roof on the annexe of the building.

Normally you wouldn't shoot in the direction of motion as it doesn't provide much parallax, but with a circular fisheye, a lot of the image is looking off to the side, so this doesn't apply.  There is, however, always a part of the image that is in looking parallel to the direction of motion. What impact this may have I don't know yet.

I crop my images to square now to save space, and have a circular mask image to mask out the edges.

So if you own a circular fisheye lens start by trying this... Go to a narrow laneway/street, walk along taking an image every metre or so, turn around and walk back taking more images. 

My test building also has a small alcove on one side.  I've shot this with a 15mm lens and it worked well, but it worked better with the 8mm, taking less images and not creating an area of excessive point density.  At longer distances from the camera, noise increases quite a bit but it's great for working in the 0-5m working distance range

Revising my shooting strategy with more tests.
« Last Edit: January 22, 2015, 01:01:01 AM by bigben »

Kiesel

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Re: Taking fisheye to the extreme
« Reply #2 on: January 22, 2015, 01:16:25 AM »
Indeed very nice results from a fisheye lens! Thank you for posting.

Karsten

bigben

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Re: Taking fisheye to the extreme
« Reply #3 on: January 22, 2015, 03:36:21 AM »
One more screengrab with the cameras visible and some thumbnails.  I was testing a few ideas to see what would and wouldn't work, including underneath the picnic table  ;)  The other thing that may be of interest... this is about an hour's worth of shooting.... and for reference, this is the location: https://www.google.com.au/maps/@-37.799871,144.9604602,169m/data=!3m1!1e3?hl=en

I'll generate a dense cloud over the weekend and put up some models of different sections for evaluation. 

Currently running a dense cloud on my other test subject... the atrium of the Melbourne School of Design.
http://thedesignfiles.net/2015/01/melbourne-school-of-design/

ThomasVD

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Re: Taking fisheye to the extreme
« Reply #4 on: January 22, 2015, 04:29:18 PM »
Would be a good procedure for modeling tunnels as well.. just walk through in both directions with a fisheye cam and voila.
Anyone up for modeling the Paris Catacombs ;) ?

bigben

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Re: Taking fisheye to the extreme
« Reply #5 on: January 22, 2015, 04:46:33 PM »
Would be a good procedure for modeling tunnels as well.. just walk through in both directions with a fisheye cam and voila.
Anyone up for modeling the Paris Catacombs ;) ?

I was thinking of different configurations of multiple cameras on a pole. In this case, you'd only need two cameras, one pointing forward and one back. Might be easier for tunnels to have a hoop around your body supported by straps over the shoulder.  Then you only have to walk through once.
« Last Edit: January 23, 2015, 12:17:45 AM by bigben »

bigben

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Re: Taking fisheye to the extreme
« Reply #6 on: January 24, 2015, 12:05:55 AM »
Here's a quick (15 minutes shooting time) test of a graffiti-filled laneway.  I failed to consider that the main parts of the image that are used for the reconstruction with this camera orientation are the outer portions. To get better overlap in these parts I should have reduced the distance between shots. 

With a relatively flat ground there wouldn't  be much need to shoot in the reverse direction for the ground close to the camera. Taking two shots at 45° to the camera path would provide more overlap at the sides as these images would also include 45° behind the photographer.  There are a few other practical considerations.... more testing to do.

ThomasVD

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Re: Taking fisheye to the extreme
« Reply #7 on: January 24, 2015, 11:58:24 AM »
Looking good, thanks for the updates :)

bigben

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Re: Taking fisheye to the extreme
« Reply #8 on: January 24, 2015, 01:16:40 PM »
Put the MSD atrium (high) dense cloud online using Potree.  http://files.digitisation.unimelb.edu.au/potree/pointclouds/msd-atrium.html
Some quick nav tips... mouse scroll wheel moves backwards/forwards. Right mouse button pans, left button rotates. It gets interesting once you move into the middle of the model

This was about an hours shooting with no really structured plan, more of a suck it and see.  Camera path was a grid over the floor and along the stairs and balconies, camera pointing in the direction of travel. Bits have worked well, others haven't.   It was a bit ambitious to have such a large space work with an untested idea, but it was a very informative exercise.  I found it very hard to stop shooting and even did a single camera path down the stairs to the floor below.

Running the dense cloud for the gatehouse shoot at max density. I'll probably do my next test with multiple cameras on the gatehouse before returning to the atrium.

bigben

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Re: Taking fisheye to the extreme
« Reply #9 on: January 26, 2015, 02:31:48 AM »
Found one glitch that I think is caused by having the direction of travel within the frame.  The light coloured points circled in the image are along the camera path when I was walking towards the large window, which was overexposed. Masking out the windows would have been one options, although a bit fiddly.  Also thought it might be a good idea to mask out a small circle from the centre of the image, thus masking out the area of image with very little parallax change between images.

ThomasVD

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Re: Taking fisheye to the extreme
« Reply #10 on: January 26, 2015, 12:38:50 PM »
I suppose glass surfaces always remain difficult. You could try mounting a polarising filter on the camera? http://en.wikipedia.org/wiki/File:Polarizer_Through_Glass.jpg

bigben

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Re: Taking fisheye to the extreme
« Reply #11 on: January 26, 2015, 04:52:45 PM »
I wasn't expecting to get the outside of the building as I'd let it blow out.  In the previous screengrab you'll notice a large hole in the wall that is a window.  The desks and computers behind it showed up pretty well as the reflections weren't too bad.  With a circular fisheye you'd lose too much fov by putting a filter in front.  ... The extra fov also poses an additional problem in that the polariser will only be effective for removing reflections at a certain angle and you lens is now looking a a much wider range of angles.
« Last Edit: January 27, 2015, 02:12:07 AM by bigben »

bigben

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Re: Taking fisheye to the extreme
« Reply #12 on: January 27, 2015, 02:55:58 PM »
Still waiting for the dense cloud of the gatehouse and preparing some images of another test.  Reduced the spacing between shots to ~75cm which seems to work well for a working distance of around 1m.  It's nice to see how much area you can cover quickly. Attached image is a medium quality dense cloud from just 15 photos (yes, I'm impatient  ;))  This building also has some dark areas so I tried using aperture priority for exposure.

Watched the shutter speed as I walked and took smaller steps if necessary to keep the exposure differences between consecutive photos to be around 1/3 stop so that was a better chance of getting good tie points between light and dark areas.

bigben

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Re: Taking fisheye to the extreme
« Reply #13 on: January 28, 2015, 07:22:57 AM »
Here's a cropped model of the building I started this testing with. https://skfb.ly/CJpR This demonstrates some of the good points a bit better as well as some of the limitations and things I need to change.

bigben

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Re: Taking fisheye to the extreme
« Reply #14 on: January 29, 2015, 10:30:10 AM »
Finally got the point cloud up...
http://files.digitisation.unimelb.edu.au/potree/pointclouds/gatehouse_8mm.html

This includes areas cropped out for the sketchfab model.  The next step will be a proper run with multiple lenses to try and put my new shooting strategy into practise. Considering the Polly Woodside as a challenge http://www.pollywoodside.com.au