Originally posted by Rondec
Finally, I think the biggest argument is the "good enough" argument, which is that getting people to buy interchangable lens cameras when their cell phone is adequate for their needs is going to be tough. People want something they can take selfies with. Can you do that with your D800, even if you had connectivity?
People are going to have the same aversion to taking selfies with any DSLR, not just FF. When they see a deficiency in their phone, they'll be looking to add a real camera for those times, and they will be more willing to spend $1000+ to do so if there's a large delta between a 2020 phone and a 2020 camera. FF gives that large delta.
Think of it this way - assuming you upgraded from a P&S to a DSLR at some point in the past, why did you do so? Those same upgrade reasons will exist in the future, and people are not going to necessarily want to upgrade to a camera that barely trumps their (probably realy good, by 2020) camera phone - they're going to want to see a real upgrade in quality and performance if they're going to spend the money.
At the same time, manufacturers are going to want to keep the $1000+ price point, and they're going to want to get aps-c and smaller DSLR/MILC shooters to stay on a body upgrade path, so they're going to bring FF down to the $1000, $1500 point to do that. Upper-end aps-c (especially DSLR) gets squeezed when that happens.
What does that portend for a company (Pentax) who's trying to sell lenses for an aps-c DSLR mount? (hint: bad things... unless they're selling FF at the time.)
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