Saturday, May 2, 2015

Playing with the new panorama stitching mode in Lightroom CC/6

I've been playing extensively with the new panorama tools built in Lightroom CC/6 that just came out a few weeks ago. The quick and dirty conclusion is that it is not so useful for what people normally do with it, which is horizontal panoramas, but it is extraordinary at stitching the high resolution composites I like to do. Let me elaborate on this. Traditional horizontal panoramas are made by somebody panning (preferably on a tripod) the camera horizontally. What you would do is select the individual shots in Lightroom and then hit Photo-Merge->Panorama when you right/control click on the images. This brings up a simple dialog after a short while where you can select the projection and output your image. The good and the bad of this:
The good:
  • Generates a 16-bit floating point pseudo raw file (a dng). This allows almost full control of the resulting image concerning white balance, shadow/highlights, etc. without any loss of quality. This is extraordinary and quite unique. Everything else will render a white-balance baked in file including my preferred method using hugin.
  • Uses the full resolution of the input file
  • Corrects for lens distortion, vignetting, aberration, etc. all automatically
  • Corrects for exposure automatically
  • Stitches are very high quality - I wonder what algorithm they use as it is different than Photoshop's merge to pano.
The bad
  • Generates absolutely gigantic files with no way of generating a slightly smaller scale. It needs a slider with a resolution multiplier (i.e. 0.5, 0.25, 0.1, etc.)
  • Very easily generates curvy horizons with no way of correcting this. This is the main issue in my opinion why it is not good for simple horizontal panos. If your horizon is not in the middle of the images it almost always generates a curved horizon. This cannot be corrected in any way as Lightroom lacks the adaptive wide angle filter you would use in Photoshop and the dng files generated in Lightroom cannot be directly edited without rendering them to tiff in Photoshop. The interface needs a way of dragging the images up and down to give you more control over this. The gold standard for panoramic stitching: hugin, does this with a few clicks and drags.

Interestingly, these pros and cons actually make it extraordinarily good at stitching the high resolution composites I have blogged about before (see for example this post). These are images that are built up from several rows of individual images. You will want to select the rectilinear projection (i.e what Lightroom calls "perspective"). An example is the below image that I never stitched before from False Kiva in Canyonlands National Park, an extraordinary place that is not shown on the park map or any of the USGS or USFS topo maps. The composite was done using 12 images arranged in 3 rows of 4. Each image was shot at 70 mm, f/16, 1/100 and ISO 100 using a Nikon 24-85 mm f/3.5-4.5 lens.

I on purpose left the images undeveloped and as you can see I exposed for the highlights not to blow out as you should always do with digital images. I simply selected these, let Lightroom put them in a panorama with perspective selected. What came back into Lightroom was a 14722x15848 pixel image (after cropping). I only had to rotate it lightly to get the horizon straight, change the white balance to a more appropriate value and play with shadows and highlights and here it is:

"Window on the world", stitched from 12 images from a Nikon D600, Nikon 24-85mm f/3.5-4.5 at 70mm, f/16, 1/100s, ISO 100.

To show you the incredible detail in this image, here is a closeup near the center of Candlestick tower, a prominent landmark on this side of Canyonlands.

Note that on a typical display, you are looking at a print of 12 ft x 13 ft or 3.6 x 4 meters, which is higher than a single story of a typical house! The slight softness you see here is owing to the fact that the lens was focused at the hyperfocal distance and not infinity and I was shooting at f/16 where diffraction should be evident.

So if you make high res landscapes using stitching, give Lightroom a try. The great thing is that it gives you a very flexible dng file that you can edit like any raw file with much more latitude than if you stitch with any other piece of software. The only "disadvantage" is that the image you'll get is absolutely gigantic.