QTVR panos with a Zenitar fisheye.

QuickTime VR panoramas with an MC Zenitar 16mm fisheye.

Copyright © 2001-2007 NK Guy

Please note that this page now has a new URL; noted below.

http://photonotes.org/articles/zenitar-panoramas/
Last year I tried shooting some QuickTime VR panoramas using a 20mm lens. I shot three and was able to stitch them together. It wasn’t a total success - I didn’t understand the importance of rotating the camera around the nodal point of the lens back then, so the photos had pretty bad parallax error - but it was a lot of fun.
Unfortunately some rat bastard burglar stole my 20mm lens, so I was sort of resigned to not being able to shoot any more panos this year. However, I picked up an inexpensive Russian-built manual full-frame fisheye lens - the MC Zenitar 16mm f/2.8.
Anyway, I got to thinking - could this lens be used to shoot QTVR panos? At first glance it seemed like the idea wouldn’t work. Apple’s QTVR Studio application does not accept fisheye lens input, and a rather aggressive American firm named IPIX have been trying to enforce their fisheye lens immersive photography patents through use of threatening letters and lawsuits, thereby preventing a lot of other firms from making software that can accept fisheye lens pictures.
This legal action is particularly troubling since there’s a lot of prior art on the topic of fisheye lenses and panoramic computer imagery. Fortunately for us, two software authors have produced very interesting tools to enable ordinary folks to use fisheyes to take panos without being forced to use IPIX’s products.

Useful fisheye software.

The first is PanoTools, a suite of software from Helmut Dersch in Germany. It allows you to do all kinds of wacky stuff, and includes a variety of stitching tools and other utilities. Unfortunately it’s as complicated to use as it is powerful, and I wasn’t sure I really wanted to embark on trying to learn it.
The second program was more interesting to me. It’s called DeFish, and is written by Ken Turkowski, an American who works for Apple Computer in the US, where he happens to develop QuickTime VR software. I find it particularly interesting since it’s a relatively easy to use program that can alter fisheye output so that QTVR Studio can handle it. However, it’s Macintosh-only, unlike PanoTools, which has been ported to a variety of computer systems. Luckily for me that’s not a problem.

Shooting a test.

First I shot a test. I went to Stanley Park here in Vancouver, set up a tripod with a pano bracket, and shot a series of 8 photos using a Canon EOS 10s camera with the Zenitar fisheye. The weather was pretty drab and grey, but at least it wasn’t raining, so I was able to get my shots. I set the camera to portrait orientation to maximize the vertical coverage of the photo.
Ken Turkowski had suggested that the vertical field of vision (FOV) of the fisheye lens in portrait orientation was probably in the 130 to 140 degree range, with the horizontal FOV being around 93 degrees. So I shot 8 pictures at 45 degree intervals. I might have been able to get away with one or two fewer, but 45 degrees is an easy angle to rotate whereas something like 51.4 degrees is not. Anyway, the more overlap the better, up to 50% or so I understand, for stitching accuracy.
I got the negs scanned for cheap at a local drugstore. The quality is pretty awful, but I didn’t want to spend a lot of money on this simple test. I then threw the colour-corrected (since the photo was taken late in the day there was a lot of skylight causing a blue cast to the photo) source photos into QTVR Studio in order to see what it would do.
First fisheye panorama test.
The final result looked surprisingly good at first glance. But then I noticed some severe problems. For example, one of the totem poles was almost entirely missing except for part of one wing floating ghostlike in the air. Not so good. And not the least bit surprising. Check out two of the files that QTVR Studio has to overlap:

As you can see the totem pole with the wings is in two utterly different and incompatible positions. So there really isn’t very much for the poor merging program to work with, and it ends up just faking things by blurring the various source files together as best it can.
So I decided to try out DeFish.

DeFish.

DeFish allows you to load up image files and apply a variety of transformations to them. The procedure goes like this:

Open the first file in the panorama using DeFish. Do this either by droping the file icon onto the DeFish icon or using File > Open. I did have trouble once dropping the icon, (the Finder claimed that the program didn’t exist) but the File menu is obviously a safe choice.

Select Warp > Choose Settings > 16 mm max perspective.

Select Warp > Create Perspective. Your computer will chug away and then open a window with the dewarped image.

Save the image to disk using File > Save... DeFish will save your photo as a PICT file. As far as I know there’s no way to specify another format, so you may need to batch-convert these files to TIFF or whatever later on.

Now you can take the dewarped images and stitch them together. Once again I used Apple’s QTVR Studio.

Problems.

Unfortunately I ran into some problems.

First, stop-down metering turned out to involve a fair bit of fiddling to figure out, since my Canon EOS camera isn’t meant to work with all-manual lenses like the Zenitar. For more information on stop-down metering check out my manual lens on EOS cameras page.

Second, the vertical field of view of the fisheye in portrait configuration was so immense it turned out that the tripod itself was appearing at the bottom of each photo. So I had to go in and Photoshop it out of half the frames - a small price to pay for such great coverage, in my opinion. One of the more egregious examples, from my second test photo shoot is shown below:
QTVR Studio unexpectedly quit when I tried to stitch the images. Reliably every time with an error of type 2. After fiddling around and scratching my head for a bit I realized that the new files were very big. (the original files were 1028 x 1536 pixels in size. DeFish increased them to 1314 by 3425 pixels in size.)
Reducing them in size by 50% solved the crashing problem.

DeFish lowers the quality of the image when it stretches it. This is kind of inevitable given what it’s doing, of course. The original image is on the left, the DeFished image on the right.

But it also appears to alter the colour quality of the file. Rather than apply the Photoshop image processing before DeFishing I’m going to do it after. Compare these two files. The image on the left is the original and the image on the right is the DeFished version. (I didn’t adjust for size, so the original images are slightly larger)

The colours are quite washed out on the latter image. I’m not sure what’s up with this - going to have to do a little more work. It might be a gamma problem.

Even once I’d got the successfully DeFished image into QTVR Studio it wouldn’t line up quite right in the stitcher. I don’t know what’s causing this - if it’s an issue with the lens, if the equations used by DeFish don’t precisely match the characteristics of the lens, or what. I’m presuming it’s the latter and a lot of fiddling and experimentation might eventually resolve things. As you can see below, if I align the winged totem pole the outer poles start to bend off in different directions.

Usually I was able to get stuff in the middle to line up OK, but the further you’d get above or below the centre line the worse things got. Have a look at these trees. Quite a bit off, as you can see.

Finished panorama.

In the end I was able to get an acceptable panorama together. Not brilliant - there are problems with the trees as noted above, which leads to some ghosting at the top. And the image is still rather muddy and not as crisp as I’d like.

Of course, it isn’t a particularly brilliant panoramic subject, as there isn’t much in the foreground, one side has a huge boring expanse of gravel, and the sky is overcast and spectacularly dull. But it was a useful testing point.

Final first panorama test.

English Bay - second panorama test.

A couple days later I drove over to English Bay on a much sunnier evening. I took a few photos near the large stone Inuit figure on the beach and made that into a panorama. Here’s the result.

Second panorama test.

It’s a bit more interesting, though the auto colour correction applied by the cheap drugstore scanner has lead to an awful magenta cast to the clouds and sky in one segment. I need to go in and fix that. There’s also a ton of glare from the sun, but that was expected - I wanted to shoot a panorama with the sun in the picture to see how the fisheye lens would deal with it. Not particularly well, as you can see - a huge patch of the sky is totally white because of lens flare.

I also need to go back and resize the thing - it starts out rather small. But the file size is pretty big, so you can zoom in quite a way.

Conclusion.

Turns out that using the Zenitar lens to slap together simple panoramas isn’t particularly difficult at all. Nor, at only 8 frames per pano, is it that time-consuming or expensive. As an additional bonus you get far greater vertical field of vision than with most rectilinear lenses.

There are problems with image quality and with poor image-matching at the extremes of the frame, but I presume these are addressable through Extensive Fiddling.

I also wonder if it’s possible to do cubic panoramas using a fisheye. I assume it is, but how easy it is is another question, I’m sure...

Useful links.

Helmut Dersch’s PanoTools site.
Panotools.org.
QuickTime VR Authoring Tricks.
Making Environment Maps from Fisheye Photographs.
No IPIX.

- NK Guy, PhotoNotes.org.
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