I would say it depends...
- Higher magnification usually results in the ability to capture more "detail", as the details you're trying to capture become larger relative to the resolving power limits of your system.
- However, it is also harder to capture a sharper image as the focal length increases unless you can counteract the effects of motion blur by using fast shutter speeds and a stable tripod*. But then do you have enough light so you don't have to crank up the ISO?
- Also, most consumer grade lenses' resolution drops as the focal length increases (especially wide-open), so the relative benefit from increased magnification is decreased. You can stop down 1-2 stops to preserve some resolution, but by then you're at f/8-11 and now your shutter speed and motion blur becomes more of an issue.
- At high magnifications, seemingly little things like atmospheric haze and scattering become more apparent and have increasingly detrimental effects on your resolution
- Beware the effects of extreme downsampling. You can have Gigapixel image resolution on capture, but at what resolution are you presenting / viewing that image? Resizing/resampling images is a destructive process like noise reduction and sharpening that obliterates the original pixel structure of your image. You're mathematically reconstituting the pixel structure of your image whenever you downsample, and when you go to sharpen/USM the downsampled image as you inevitably have to, you will again disrupt the pixel structure. In order to see those now tiny details that were once captured at a much larger size, you need to sharpen significantly. And now those heavily sharpened micro-details look kinda funny now.
- The moral of the story here is that above a hundred megapixels of capture resolution, presentation size / resolution becomes by the limiting factor, not capture resolution. And no amount of photographic or software trickery can address that. Monitors are essentially useless; you need to print, and you'll need to print large. Very large. From a wide format printer that most people can't afford at home. $200 prints + $200 mounting & framing as a start.
- So to answer your question about using a 100+ mm lens to capture a Gigapixel image, I would probably use a 50 mm instead unless you have the ability to produce massive prints.
* - Speaking of tripods, with panos, the issue of parallax and shooting around the nodal point is something to think about. It isn't something to worry about if you use a lot of overlap and don't have anything in the foreground that is prone to parallax shifting, but something you should know.
