Finding the Non Parallax Point - Panoramic photography

[marcal]

Hi there,

I'm introducing myself to the panoramic photography. In order to get started I purchased a Panosaurus head (which is a really good value for the money you pay for it). I calibrated my 18-50 EF-S lens without any problems. Then I tried to calibrate (find the NPP) my other lens, a Tamron 55-200. I found that I was only able to calibrate it up to 100mm of focal length. Any further than this, I was unable. I asked the manufacturer and he told me that it can be that, dependig on the geometry of the lens, one is not able to find the NPP for all the lengths.

Does anyone have experienced something like that? Any experiences with this lens?

Thanks in advance!

[inkista]

No experience with that lens, but I use a Sigma 8mm f/3.5 circular fisheye, and it changes its no-parallax point depending on the angle of yaw rotation (i.e., if I'm taking four shots around a 90° intervals, I have to use a different point than if I'm taking six shots around at 60° intervals). So, yeah, a shifting no-parallax point is not unknown or uncommon, even with prime lenses. :/

The thing is, that in practical usage, getting a perfect no-parallax point is often irrelevant. Stitching software can correct for certain amounts of parallax error, so if you get "close-enough" it can still all work, as long as you're using a stitching package with some leeway in it, rather than just using layers or something to combine images. I regularly shoot handheld panos with my fisheye lens, and while I do get stitching errors from parallax, they're typically patchable, as long as I wasn't too wildly off or in too small a space.

[marcal]

Thanks for your reply. I, too, have observed that handheld panoramas also look good. Still it puzzles me all this trouble with my lens because, what I love is those gigapanos where you can zoom in endlessly. It's a shame I can't afford a nicer lens.

BTW I'm using autopano giga on my iMac.

[OsmosisStudios]

Originally Posted by marcal

Thanks for your reply. I, too, have observed that handheld panoramas also look good. Still it puzzles me all this trouble with my lens because, what I love is those gigapanos where you can zoom in endlessly. It's a shame I can't afford a nicer lens.

BTW I'm using autopano giga on my iMac.

Gigapanos arent done using super wide lenses: they're done with fairly long lenses. most gigapixel panos are done with thousands of shots.

[marcal]

Originally Posted by OsmosisStudios

Gigapanos arent done using super wide lenses: they're done with fairly long lenses. most gigapixel panos are done with thousands of shots.

That's why I would like to use 200mm instead of 100mm

[inkista]

Was googling around, and saw this thread on the Max Lyon forums that suggests your no-parallax point might actually be negative (i.e., behind the lens, rather than inside it).

The thing is, parallax only becomes a problem to stitching if you're shooting foreground objects that are close to you. If the majority of your scene is far away, then parallax isn't likely to be much of an issue, and you can just use the pano head to track coverage, with more precise rotating in yaw and pitch.

The no-parallax thing is more critical for folks like me, who do spherical panos, rather than gigapixel panos. If I'm shooting in a very tight space (say a doorway or stairwell), then I have to be very careful and use a panohead and even then, I can still get parallax errors. At those close distances, even being a millimeter or two off can make a huge difference. Because I use a fisheye and only shoot a handful of member images, I may not have enough overlap to clean up stitching errors in the final pano.

[marcal]

LOL, I asked the same question in the kolor.com forums and I got the same link from another user, haha.

Thanks for your input, I really apreciate it. I'll take it into account. Nevertheless, it would be nice to be able to calibrate the whole length range on my lens, but I have to assume that I can't change the laws of physics.

Cheers!

[inkista]

Well, the whole point of a telephoto design is to make a lens shorter than its actual focal length.

And yeah, you're going to get generalized help like that from generalized boards. You may want to hit a more pano-specific forum like the Max Lyons group (where the whole gigapixel thing got started), or a gigapan group--that's where the expertise is going to be. For more generalized photography questions it makes sense to seed 20 boards and see what pops up, but for the specialty stuff like this, I think a more targeted approach probably gets you more meaningful information.