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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Rendering Fisheye to Rectilinear?

Hey everybody - thought I could contribute to this post. I've used Shake to correct out lens distortion on several occasions. The workflow is very straight forward. Make sure you cam is straight and level and the frame filled w/ a grid-ish pattern (horz and vert straight lines - but you don't need many). Then w/ the lens distortion node you tack out a few splines on the curving lines of the grid in a couple parts of the frame.

The node assumes those lines should be straight and creates a correction algorithm for that. Once you have your lens dialed in, you should just be able to use the values generated in future corrections.

-JF

www.jfernsler.com
 
Bruce Allen said:
Hopefully at some point there'll be a Mac-based compositing program with built-in support for texture projection on true 3D objects / bicubics.
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Nuke can do this and runs on most OS's:
http://www.thefoundry.co.uk/promo/nuke.html

It was Digital Domain's in house compositor and just recently moved over to the Foundry to support. It doesn't have the prettiest gui nor is it cheap, but it is damn fast.
 
deke,
shake guy, fusion hater.
Put a grid in front of it
 
Welcome to the forums Deke. I hope to see more of you in these parts. Are you looking into renting/ordering a RED for yourself or just looking at the post implications?
 
There's lots of photo tools out there to convert between fisheye and rectilinear. But if we're talking video or even RED footage, then it's more involved, obviously.

Some basics, with some simple tools for stills are mentioned here. But this is a good page that shows you what's going on in such a conversion. http://photo.net/learn/fisheye/ ...Funny, it comes up as the first page in a google search with "fisheye rectilinear conversion", but I found this page a few months back in a semi-related search.

I think there are several ways to approach this sort of conversion, but a high end tracking and match moving software or compositing app is probably the way to go. Nuke is great, 30 day free trial too, but it is overkill to buy just for this purpose. These tools often need a lot of tweaking anyway or will need to know specifics about the optics being used or adjusted by sight until it looks right. Not all fisheye lenses have the same level of distortion or same FOV -- a 10mm Nikon fisheye is different from a 10mm Peleng. ...Same with rectilinear optics.

Personally, I would hack out a solution using a 3D app myself. The basic concept (in brief description form)... Similar to what jfernsler mentioned, I would make a board with a grid on it. Shoot it with the fisheye lens, then shoot with a rectilinear lens. That will give you the line basis for distortion on a 2D plane. In your 3D software, create a flat plane on which to project your image. Use a UV map to distort the projected image based on the grids you shot -- you could set up a UV map for conversion to rectilinear and another to convert to fisheye. Tweak to your liking, set to render with an orthographic camera setting directly facing this distortion plane. offsetting the axis of the view camera from this plane can compensate for perspective adjustments and positioning for a direct crop while rendering out.

If you don't have any 3D software at your disposal, then you're back to the point of finding and learning new software. This may be a bit more involved than you would like if you don't need the 3D software for other uses... But there's some better pricing options here vs. Nuke or similar apps. For 3D apps, Blender is free, some others that will handle this task can be had for under $1K.
 
im.thatoneguy said:
Welcome to the forums Deke. I hope to see more of you in these parts. Are you looking into renting/ordering a RED for yourself or just looking at the post implications?
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Mostly post implications and if I shoot stuff it would just be a rental. It's always nice to know all you can about the camera that your material is coming out of that your going to matchmove, comp, etc.. on.
 
Jeff Kilgroe said:
Nuke is great, 30 day free trial too, but it is overkill to buy just for this purpose.
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I disagree. We're not talking about a single frame here. If you have a Red and need to undistort thousands of 4k files. Then doing it in 3d or some other software could possibly cost you months of processing time. $3500 is not so bad anymore if it only takes you 1/10th the time.

Though Stu does DI in After Effects, so you can use anything you want if time isn't an issue.
 
dekekincaid said:
I disagree. We're not talking about a single frame here. If you have a Red and need to undistort thousands of 4k files. Then doing it in 3d or some other software could possibly cost you months of processing time. $3500 is not so bad anymore if it only takes you 1/10th the time.
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I know Nuke is fast -- I've played with the trial some, will probably buy it once I have a project that needs it. Shake is still working for me now. Anyway, the 3D app approach wouldn't be any slower once you have the basic template files set up. It's just a more manual setup and creation to the process and this will take more time on the front end. I know I'd want a whole day to set up such a conversion in Lightwave, XSI or Maya... By the time I run off a grid on a large printer / plotter, shoot it with both lenses, build the 3D scene files, run some tests, tweak, test, tweak, etc... Definitely not a luxury available in all situations.

But like you said...
so you can use anything you want if time isn't an issue.
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Hmm..

the fastest way I can think of doing it is using Defish to unwarp a 16bit UV gradient.. and then using shake to displace your frames onto that warped UV..
that way you get the warp from Defish.. but your processing in shake....

I can explain that in more detail later...
 
Why not shot with a rectilinear lens in the first place ?. Zeiss has the Ultraprime 8R (R for rectilinear) and I believe in their webiste there´s a comparision with a Nikon fisheye besides some other examples. If you´re going to need this for a couple of shots, you might get it cheaper by using the right lens than going through the post path.

Regards

Rodrigo
 
Rodrigo Lizana said:
Why not shot with a rectilinear lens in the first place ?. Zeiss has the Ultraprime 8R (R for rectilinear) and I believe in their webiste there´s a comparision with a Nikon fisheye besides some other examples. If you´re going to need this for a couple of shots, you might get it cheaper by using the right lens than going through the post path.
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Totally agree, except that the post path isn't THAT expensive. I did a rough recilinear conversion of the Peleng Matt Uhry posted in about 15 mins in After Effects (includes project setup time - now I'd be good to go really quickly):
http://www.boacinema.com/projects/red_stuff/peleng_rectilinear.jpg
http://www.boacinema.com/projects/red_stuff/peleng_rectilinear_overview.jpg

The problem is quality (especially if you are going for ultra-wide like I was in my rough example above - all the detail is in the center). But if you're shooting, say, a promo in SD, then the quality should be sufficient. Get a cheap computer, use it to convert the frames overnight... should be fun!

I think it's fun to explore this as a nice new option allowed by 4K capture. Eg, it would be hard to do this specific trick even for an SD finish if your source material was from a regular HD camera and not a Red. Not that there aren't other ways to get the same result using film, multiple HD cams, etc, of course!

Sorry. Bit of a backwards-worded post, this ;)

Bruce Allen
www.boacinema.com
 
... and here is an approach to the problem with the Peleng frame done in a 3D package, with pan/tilt/zoom applied to the image and then rendered to SD...

The image is mapped into a sphere, the camera centered into the sphere panning/tilting and zooming to re-record.

Plenty sharp enough for SD even with fairly tight FOV's...

http://ftp.datausa.com/imageshoppe/outgoing/RED/FISHEYE-to-SD.mov
 
Rodrigo Lizana said:
Why not shot with a rectilinear lens in the first place ?. Zeiss has the Ultraprime 8R (R for rectilinear) and I believe in their webiste there´s a comparision with a Nikon fisheye besides some other examples.
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I think it really depends the look your going after. Anyways, isn't the smallest rectingular is only a 14mm where a circular fisheye goes down to 8mm?
 
The Canon 10 to 22 would work great. Very sharp, with simple first order distortions, easy to correct to perfect rectilinear if necessary. The Sigma 10 to 20 is also good, but more complicated distortions to correct.
 
Jim Arthurs said:
... and here is an approach to the problem with the Peleng frame done in a 3D package, with pan/tilt/zoom applied to the image and then rendered to SD...

The image is mapped into a sphere, the camera centered into the sphere panning/tilting and zooming to re-record.

Plenty sharp enough for SD even with fairly tight FOV's...
Click to expand...

Agreed!

dekekincaid said:
I think it really depends the look your going after.
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Agreed!

dekekincaid said:
Anyways, isn't the smallest rectingular is only a 14mm where a circular fisheye goes down to 8mm?
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Don't agree - as mentioned above, Arri / Zeiss makes rectilinear 8mm.
http://www.arri.com/prod/cam/img/acc_smal/ultra_8r_s.jpg

Jim Arthurs said:
The Canon 10 to 22 would work great. Very sharp, with simple first order distortions, easy to correct to perfect rectilinear if necessary. The Sigma 10 to 20 is also good, but more complicated distortions to correct.
Click to expand...

Agreed again!

Bruce Allen
www.boacinema.com
 
Canon 10-22

Canon 10-22

Jim Arthurs said:
The Canon 10 to 22 would work great. Very sharp, with simple first order distortions, easy to correct to perfect rectilinear if necessary. The Sigma 10 to 20 is also good, but more complicated distortions to correct.
Click to expand...

Jim:

Are there motion picture solutions to fixing Chromatic Aberrations in the 10-22 (as well as others) like there are in the still photo world. That is there are programs/plugins that make this a very straight forward process with stills. It seems like you could batch process or that programmer could write a specialized version for motion pictures, but I was wondering if there is something like this already out there?
 
Sure, as Bruce mentioned in another thread, with After Effects,

http://www.reduser.net/forum/showpost.php?p=95310&postcount=13

another choice is a fairly non-user friendly product called PanoTools (works with Photoshop) which is cross-platform and perhaps other ones in other compositing programs.

Just as an FYI, the 10-22 isn't all that bad with CA...

http://www.photozone.de/8Reviews/lenses/canon_1022_3545/index.htm

Now, in the idea world, REDCINE would have the ability to deal with CA, distortion and vignetting as part of the export process... maybe someday...
 
Jim Arthurs said:
Now, in the idea world, REDCINE would have the ability to deal with CA, distortion and vignetting as part of the export process... maybe someday...
Click to expand...

Bruce mentioned, earlier in this thread, that he could possibly develop a RedCine plugin to do this.
 
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