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Fev
08

dos mundos redondos.

acabei de receber do spark um link para umas fotografias em um site em russo. olhando pras fotografias, dá muita vontade de entender russo só para saber como essas fotos foram feitas! o efeito é esquisito, porém interessante. dá uma olhada:

weirdphoto.jpg

eu disse que era esquisito… pra conferir as outras fotos, é só clicar.

ATUALIZAÇÃO: descobri como faz. ;) como nunca se sabe quando essas coisas podem sair do ar, para ler a explicação completa é só clicar abaixo. quem sabe alguma hora dessas eu aproveite para traduzi-la… quem sabe…

To build a 360°x180° panorama you have to take pictures on all directions, but not only on the horizon. You should also shoot the sky (zenith) and the ground (nadir). A missing zenith is not important if you only plan to build a planet.

This initial panorama is built from many individual pictures with the following tools:
* autopano-sift to create control points,
* hugin to figure out, from the control points, how each picture should be distorted,
* enblend, to stitch the distorted pictures together.

Rob Park’s tutorial about the above tools really helped me when I started making panoramas (I have a separate set for “straighter” panoramas). Unfortunately Rob has removed this tutorial from his site. You can still read the text, without the pictures, at webarchive, however today it might be better to start from the list of Hugin tutorials.

Converting the panorma into a planet can be done in different ways:
* Dirk Paessler posted a tutorial showing how you can use the “polar coordinates” filter of your photo editor (The Gimp has one)
* Sébastien Perez-Duarte (Seb Przd on Flickr) explored stereographic projections instead, and I find it usually looks far better. Consequently, that’s what I’ve been using too. This can be achieved with the mathmap plug-in for The Gimp. (Do not use the “stereographic projection” that comes with mathmap, it doesn’t do what you want. Just work from this formula.) Mathmap has a group on flickr where you can ask your questions.
If you can’t stand maths, or can’t use mathmap, you can also achieve the stereographic projection using hugin. Please refer to Manu’s explanations.

While I’m now using a DSLR on tripod with a panoramic head, my first planets were shot handheld with a point-and-shoot camera.

I have been shooting handheld until 2006-11-12, at which point I bought a simple tripod without panoramic head. Even though the tripod won’t rotate the camera around its nodal point, it still helps to reduce the errors. My brother then offered me a panoramic head which I’ve been using since 2007-01-01: no more parallax errors.

The first 48 planets (shot and uploaded before 2007-02-17) were all shot with my
Sony DSC-T5 point-and-shoot camera. The problem of this camera is that there is no way to lock the exposure, so the 50+ shots it takes to make a panorama are all exposed differently. At some point, Seb Przd pointed me to PTblender as a way to adjust the color of a picture to match its neighbor. Using PTblender to color correct an entire panorama is difficult as time consuming (see this comment for a description of my technique, this comments for an interesting side-effect, and this picture for some time estimation). I then bought a DSLR (Pentax K10D), so it’s likely that all panoramas taken after 2007-02-17 will be shot with it. I have been using the K10D kit’s 18-55mm lens until 2007-04-07, I’m now using a Pentax 10-17mm fisheye lens.

There is a last tool I’d like to mention here: I use exiv2 to copy the EXIF data from one of the shot into the final panorama. This way flickr knows when the panorama was taken, and people can look at it if they want.

If you have some questions, other people may have the same: so please do not send me private mail, ask publicly. I suggest you ask technical questions in the Create your own planet, Equirectangular, or Stereographic projection groups.


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