Thanks. All great information on the "how to". Any specific suggestions on a lens for the A7r. I do some extreme backcountry locations that require multi-day backpacks so the GigaPan is not a practical option for this application unless I pack it in via horseback. Thanks and thanks again.
Hi,
The required focal length depends on the required file resolution for output. The required output resolution is determined by the viewing distance of the print.
Example, an 18 feet wide print would probably be viewed from some 6 to 18 feet distance. If it must retain high resolution with shorter viewing distances, everything scales proportionally. Let's assume 10 feet viewing distance, easy to calculate with, then for someone with 20/20 visual acuity, the output must be printed from a 29 PPI source image (which would be upsampled to 360 PPI for printing with good output sharpening).
The 29 PPI image means that the print file before upsampling to native printer resolution would be 29 PPI x 216 inches = 6264 pixels wide. That's easy enough with most lenses that offer enough Field Of View for your scene, 2 or 3 stitched images would already allow to that. Those 2 or 3 images would need to cover the angle of view you want to shoot. If the angle of view is extreme enough to compromise the available lens quality, a longer focal length and more stitched images will be required.
However, if you need the same viewing quality at 1 foot (1/10 of the example) viewing distance, then you'd perhaps need 10x as many pixels, or something like 15-16 images with 30% overlap taken with a much longer focal length, per required Row (maybe 5 rows will suffice). If cylindrical projecton is acceptable, then not much (if any) additional resolution is required. For Rectilinear projection it would depend on the actual angle of view to cover.
So you need to determine the print viewing conditions, and the scene angle of view to cover, the rest can be calculated. Maybe a good 24mm, or 35mm, or perhaps a lightweight 50mm lens is all you need, but to determine that more info is needed.
As far as traveling lightweight, I can still recommend a click-stop indexer if you indeed need to stitch many images for the field of view you have in mind, and you could even use that instead of a ballhead or other head if you need to shave of as much weight as possible. But then a very lightweight (but with significant load capacity)
Easy Leveler II will allow to do the final leveling and composing, to finish what you started with the tripod legs. I use one mounted directly on the tripod base plate, and a Manfrotto click-stop indexer on top of that with an Arca Swiss clamp on top of that for my No Parallax Point (NPP) bar (a RRS MPR-CL II) . Multi-Row setups may require more components.
Cheers,
Bart