On Fri, 21 Jan 2022 at 21:47, johnfine2017 wrote: > > I'm trying to assemble a specific vertical panorama, but also trying to learn > methods for assembling a vertical panorama. > > One major issue (that I'm furthest from figuring out on my own) is the > exposure issue: > Taken on a cell phone (fixed F 1.9, Focal length 2.91, aperture 1.85, not > sure those even have the same meaning as on big camera) with auto varying > time:
They have the same meaning except all the dimensions are smaller for a small sensor, Hugin should interpret them ok. > Bottom photo is 0.025 sec exposing the street well and including some totally > blown out sky. > Middle photo is 0.0083 sec exposing buildings well with sky blown out and > street too dark. > Top photo is 0.0073 sec exposing the sky well. > > I definitely don't want to compress the range. I'd rather be dishonest than > correct for that. > > If the alignment were perfect, then doing no exposure correction would work > with the blending from one image to the next smoothing the exposure > transition. But I haven't gotten the alignment near that good and would like > to learn how to live with poor alignment. That involves narrower transition > zones in controlled places, which would then generate ugly exposure jumps. > > What I think I want is a height based exposure shift in each photo (rather > than the usual exposure to exposure nonlinear mapping to compress the range > without losing much detail). In each photo I think I want a smooth > transition from making the bottom a little brighter to making the top a > little darker. Then the same final pitch of each photo would match in > brightness. Hugin will by default map the exposure of the photos to the scene, meaning that it will brighten your sky image and darken your ground image so that they match the exposure of the middle image - the end result (if you stitch to an 8bit format like JPEG) is that you may as well have taken the photos on the middle exposure in the first place. Actually most of the time this is wanted, most panoramas I shoot these days are taken with my phone on auto-exposure, and I don't worry that the individual photos have different exposure times, Hugin blends them together seamlessly. But it doesn't work if you want to see the clouds and undergrowth in the same final panorama - for this you need tonal range compression - things you can do: 1. Stitch to a file format that can hold this large dynamic range, such as EXR, and 'tone map' this into a viewable 8bit image using a tool like LuminanceHDR. 2. Force Hugin to ignore the exposure recorded in the photos (and discard any fine-tuning by the Hugin photometric optimiser). Select the photos in the Photos tab, edit the Eev and set them all to the same number. It doesn't matter what this new Eev number is, but you do need to set the Eev of the output panorama to the same number, or the exposure of the output will be way-off (in the Preview window there is a little handy arrow button marked 'EV' that resets the output panorama exposure to the average of the input photos). This will give you your clouds and undergrowth visible in the same panorama, but the seams might not be exactly where you want them, so create masks that remove the overexposed clouds in your middle photo and that remove the underexposed buildings from your sky photo - don't try and follow the edge exactly, leave a bit of sky and building for Hugin to use for the transition - this will move the seam to the boundary between buildings and sky, and with luck this seam is completely invisible. > Also, is there good info on the other techniques for a narrow vertical > panorama? I don't know what projection works OK. The best I found with a > google search is to turn the whole thing sideways and use the usual methods > for that kind of panorama, then rotate it afterward. Is that really the best > way to do narrow vertical? Most of the Hugin output projections are designed for very wide angle of view scenes. You can try a fisheye projection like Stereographic, these are symmetrical and treat horizontal the same as vertical. But what you probably want is Transverse Mercator, this projection is designed specifically for tall and narrow panoramas. -- Bruno -- A list of frequently asked questions is available at: http://wiki.panotools.org/Hugin_FAQ --- You received this message because you are subscribed to the Google Groups "hugin and other free panoramic software" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/hugin-ptx/CAJV99ZhJDihqQHCnR6-%2BtiaawS5LK4XHjA2Ue2LCYTj2Vvx68g%40mail.gmail.com.
