Upload & Sell: Off
It would seem to me that the 400 2.8 IS nearly fits that description - I can stack up to 4x worth of TCs behind it and see increasing level of captured detail (on a per frame basis, beats upressing).
Of course, I lose fast AF with the 2x and no reliable AF at all beyond 2x. If a 288 MP 1.6x crop sensor arrives, I will have the luxury of throwing away my TCs and enjoying fast f/2.8 AF (with the bonus of being able to shoot at lowest ISOs). All this while achieving maximum "reach" allowed by the...Show more →
I know we are not close to the 288 MP sensor that you want, but what I love the most about the 7D is related to what you are saying. With 18 MP on a 1.6 crop sensor, the 7D is the first camera that I've used that allows me to do much of my long lens shooting with a 400 mm lens and no extenders, and the obvious advantage of that is that Canon gives us the choice of 3 relatively light weight lens options at 400 mm, and those options allow for mobility, ease of hand held shooting, etc. that cannot be realized with any lenses longer than 400 mm.
The 1D Mark IV comes the closest of any 1-series camera, both before the 1D Mark IV and since the 1D Mark IV, by allowing me do most of my shooting with a 500 mm lens and no extenders. While the 1D Mark IV has, by a good margin, the highest pixel density of any 1-series body, unfortunately, Canon does not give us any 500 mm lens options in the range of 4 pounds, like the 100-400, 400/5.6, and 400 DO. Thus, the 1-series body that will eventually replace my 1D Mark IV will not likely come until there is a 1DX Mark III with pixel density that exceeds that of the 1D Mark IV.