My interest is primarily with wildlife photography and in this thread I want to explore the near future (the next decade - if you can consider that near) of telephoto lens inovation. Over the past 2 or 3 decades telephoto lens size appears to have changed little - is this going to change over the next 10 to 20 years?In 10 years you may need 25K to buy a new lens. Prices are doubleing with each new generation of lens. Many of the used big whites sell for more than they cost new.
1. What specifically restricts lens size with existing DSLR technology? Does the distance from the sensor to the lens make enough of a difference that future telephoto lenses on mirrorless systems will be substantially smaller? (forgive me for assuming that mirrorless cameras will replace DSLR)
2. Ten years from now, when you're shooting with a 100mp mirrorless camera body, will it still be an advantage to shoot with a massive 600mm f4 lens, or will cropping to a 20mp image with a significantly smaller lens eliminate the need for a super-telephoto? There are certainly differences that will be difficult to overcome, such as tracking wildlife from a distance and accurately focusing at that distance with a smaller mm lens. Do you think these challenges will be met?
Canon has filed a number of patents over the past few years which have the effect of reducing the length of a lens, but not the diameter. So, lenses are going to be shorter.
In a nutshell, 10 years from now (when I finally have 10k to spend on a lens) will I still want to purchase a 600mm 5kg lens for optimal image quality?
The size of a lens is based on the focal length, aperture, and size of the image circle needed to cover a sensor. For the long telephotos, the aperture and focal length determine the diameter, so the sensor size has no affect.