Really wide image, stitched?

[littlemike]

I'm not quite sure which forum is the right one for this question, so if I've

mis-posted it, I apologize.

 

Say I wanted to document the entire length of a (non-moving) train which was

several hundred meters long, and could only stand back 30 meters from the side

of the train at any one point. I reckon that I'd move along the length of the

train and take individual shots, then stitch them together into one long image.

My question is about how one might eliminate the optical and lens distortions of

the individual images before stitching theme together into one seamless

(hopefully) strip.

 

I have a 20D, some good lenses, tripod, Lightroom, CS2, PTlens.

 

Thanks for any suggestions!

[jo7hs2]

Well, trains aren't part of nature, but they are made from nature, and they operate in it, so I think we can answer your question anyway.

 

Some of the stand-alone programs (Autopano, PTgui, etc...) do a somewhat better job than CS2's built-in stitching, so you might consider one of them. You definately can do what you are thinking of, but it may take some trial and error to deal with several of the problems. Ideally, you'll want to use your least distortion-prone lens that allows for the distance requirements you have. I'm not sure what I can offer regarding distortion removal beyond the use of PTlens. The only thought I have right now is that you could shoot the images in a way that allowed you to crop out the most distorted image sections, which would require a lot more work in taking the pictures, and would only correct certain optical issues.

 

I'm sure somebody more knowledgable about image-stitching and distortion removal will come along and provide you will excellent advice.

 

Great idea!

[littlemike]

Thanks, Joshua! It's really not a train I want to photograph, it's part of nature. I'm germinating an idea which is really cool, and I'm not aware of anyone having done it before me, so is it okay if I don't get any more specific than to say that the subject is really really long and has some height -- train-like?

[jo7hs2]

I don't think anybody will mind if you are a little cryptic to protect the originality of your idea. Just make sure to share the results with us when it does get done, so we aren't perpetually in the dark!

[dan_smith26]

A couple of things you might keep in mind. Exposure variations from frame to frame are killers when stitching wide images. They make a lot of work necessary and can be avoided if you are careful when setting the shooting exposure initially. A tripod really helps when keeping the camera level and at the same height relative to the subject matter.

 

Using a bit more overlap from frame to frame than you think necessary will help a lot with controlling some of the edge distortion. Also makes it easier to have matching points in each image if and when you hit areas where not a lot of contrast is available.

 

When doing the stitching you might do two or three frames at a time rather than a half dozen or so. It makes it much easier for you to see the progress as you are checking only one at a time and eliminating many small errors that can crop up in the middle of the project.

 

Best of luck with the project.

[pjmeade]

I used the photostitch software that came with my Canon camera.It worked nicely.

 

As dan points out, use a tripod, when I've tried hand holding, I enevitably dip and rise. And set your camera to manual too, get your average or best exposure and set the camera to that, otherwise you will change exposure as you pan and risk getting dark lines at image junctions.

 

Hope this helps.

 

P

[johnclinch]

You may find this useful, it describes stitching a long wall of graffiti

 

http://www.dojoe.net/tutorials/linear-pano/

 

The bottom of this tutorial describes what you want, but it describes it as impossible for anything other than a flat object. Simply put the borders of each photo have a different perspective, they simply can't be matched

 

http://slash72.club.fr/gurl/MODES-PROJECTION/en_prefecture_rectiligne.htm

 

If possible stand along way fron the object and use a telephoto lens from one point.

 

Best of luck

[littlemike]

Thanks, guys - this is all excellent info and completely pertinent. The first link that John gave uses non-Windows tools (Linux, I reckon) -- so I'll need to sort out the techniques in my environment. And I've learned that what I'm after is called a "linear panorama." And wowsers -- there are some fantastic examples of that kind of work on the second linked page.

[jo7hs2]

By the way, keep in mind that the software for combining the image will probably take FOREVER with a project of this size!

[johnclinch]

Actuall Hugin is avaible for windows and MAC as well and all for free. It is by any standardsan amazing piece of software. For example it estimate lens distortion and vignetting and correct for them, all by just examining your input images (or you can input information from the PTL lens data base). Enblend will cleverly cut round people who have moved, where possible. Everyone should have a copy

 

On the speed front I wouldn't worry. I have stitched 35 6Mp images on a computer with 512 Mb of RAM. It helps not to ask for to big an output, well at least until you are sure you need a big output. Just save the project then ask for a big output when you need it. They claim to have created giga pixel images with hugin.

[dan_hall4]

Shoot vertically unless you want a hot dog shaped image. I just got a Bogen elbow bracket for my 3011BN for that very purpose. Need to test it but feel certain that it will work. Specialized panoramic heads are out there and may be of use to you. Learn what a nodal point is. Basically, the camera needs to pivot from a center point and if it is off line from that, varying degrees of distortion will be evident in your images. I know very little about it so far or I would tell you more. It may make a difference with the project you are trying to do. Don't use a polarizing filter and be sure to use manual mode so all exposures are the same. Don't use ultra wide angle lenses. I have heard of programs running overnight to stitch big panoramics, so be mindful of that. Some of the software is very intricate. Some are user friendly stitching programs like in PS and PSE 6.0. I am learnign on that myself and can not offer any advice. Just pointing out that there are very complex systems and some that are rather simple. Lots of info on this forum in the form of old post and google. In the search box on this page in the upper right, enter panoramic. Search panoramic photo, panoramic images, etc.. on google. I found all kinds of links. Here is a few links that may be helpful. Good luck with your project and as Joshua suggests, let us see it when you finish.

 

http://www.shortcourses.com/display/display3-1.html

 

http://www.tawbaware.com/maxlyons/

 

http://www.amazon.com/Assembling-Panoramic-Photos-Designers-Notebook/dp/0596009755