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05/18/2005 05:46:49 AM · #1 |
I've done some panoramic photography over the years, some came out pretty good and some failed. The reason I haven't been producing them more often is the lack of control that the software has been giving me. I don't want to rely on the software to make seamless panoramics. Sometimes it just doesn't work, and then you've wasted your time even though you know what it IS possible. From what I've read, PanoTools can offer me exactly what I need for panoramic stitching.
Let me outline what I think a panoramic stitching session should consist of, and where I need help.
1- Take the series of pictures. Tripod obviously helps, but shouldn't be indispensable. I often get inspired for a panoramic when my tripod isn't around. Overlap by around 25%. For now, we'll stick to talking about a one-line panoramic (as opposed to a matrix panoramic).
2- Rectify the distortion. I'm willing to invest in this step, as it will surely facilitate the following steps, and prevent the computer from making stupid stitchings or freeze up during compiling. My thoughts (although I haven't even started doing them yet):
I print out, on large format paper, a series of concentric rectangles (3:2 because my camera has this crop ratio) and photograph it at many possible focal lengths, ranging between 18 and 70mm with the standard D70 lens. I then use the correct radial shift function in Panotools to rectify each image separately (make the rectangles straight edged), and note down the correction parameters. Now I have a "profile" for my lens. Please let me know if such a profile already exists.
Now, for every panoramic set of images I take, I could rectify each image seperately and save them all in a new folder (probably through the use of a script if it's possible).
3- Here is where I could only expect a computer to do this for me. Basically, I feed the files in order to the software, and flag a few pairs of points for every pair of photos, so that the computer can align all of them (ie: calculate the yaw, pitch, roll and picture-to-picture alignment) and return a psd file with the series of pictures overlaped as seperate objects.
4- I could then choose my blending mode: feathering or custom blending. Also, I could then easily do exposure corrections the image as a whole or in different parts. If the pictures were not taken along the horizon, the outcome will probably be curved, in which case I think there are some correction tools in the Correct menu that can linearize the stitched panoramic.
step 1 and 4 shouldn't cause any problems.
step 2 seems like a lot of work, is there a way around it? or some shortcut I could use?
step 3 I think I could do in Panotools, from what I've read... but I have no clue how??? Is it done directly in photoshop via the adjust menu? or is it done through PTstitch or some other java program?
Does anyone know any tutorial on PanoTools, or could give me some advice? I'd greatly appreciate that.
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05/18/2005 10:11:22 AM · #2 |
I think I can shed light on the process. I'll take it by your steps:
1- There's no real reason you have to use a tripod for landscape panos. For interior panos, where parallax is a great concern, then a tripod and pano head (rotation about the "nodal point") is almost a necessity. Let's focus on landscape panos, since my interior pano experience would fit in a shot glass.
2- As far as distortion, you may want to google a little tool called "PTLens", it's a PS plugin that corrects distortion for your specific lens. It's pretty good!
//epaperpress.com/ptlens/
That said, unless your lens produces a lot of distortion, it might not be worth correcting. I think shooting a grid of squares and running PTlens on the result would be enlightening, and will likely try it myself. I typically don't pre-correct my shots, but I typically shoot at 24mm in portrait orientation for pano work.
3- Here's the trick, get one of the GUI front ends for PanoTools. The one I use is PTGUI, which is $49 USD, and there is PT Assembler, which is, I think, $39 USD. Another option is hugin, which is an open-source, cross-platform effort that is in beta. I've no experience with PTAssembler or hugin. I think hugin has potential, and may try it out.
//hugin.sourceforge.net/
//www.tawbaware.com/ptasmblr.htm
//www.ptgui.com/
Also, here's a nice little read that covers workflow. He's using a Mac, and of course the details are specific to his software, but there's a lot of good general info there:
//vrm.vrway.com/issue20/BEGINNER_S_TOOLS_PANOTOOLS_WORKFLOW_FOR_MERE_MORTALS.html
Finally, just a comment that how the scene is captured has a great impact on the uality of the final output. Ideally, I shoot in full manual mode, with both shutter speed and aperture set as desired. White balance should be set to a constant, ideally using a white or gray card, but in any case not "auto", since that will allow the WB to shift per image, which inevitably causes problens matching color later.
If shooting hand-held, I try to rotate the camera around approximately the front of the body. this will minimize (not eliminate) parallax, and for landscapes, this is "good enough". It's NOT good enough for interiors.
Use a low-distortion lens if available, and shoot at the longest usable focal length. The wider you go, the more distortion, and the more difficult the stitch will be. I try to shoot at 24mm (mostly because the 24-70 is my preferred pano lens). I shoot portrait mode, and that gies me a 50° vertical FoV, which is usually sufficient. I overlap about 20-25%.
A few words about stitching panos where the combined FoV is really wide, approching or exceeding 180°; don't use the default projection method in PTGUI, which is rectilinear. Use cylindrical projection instead.
Edit: reposted to parse URLs...
Message edited by author 2005-05-18 10:12:02.
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