maverick75 wrote in post #17057471
Not sure if this has been mentioned but with a mirrorless system and adapted lenses you can actually make them faster and wider with pretty much no noticeable image quality loss by using speed boosters.
The metabones system is fantasic and used by world famous filmmakers, even the 3rd party knock offs are starting to be really good.
I mentioned focal reducers earlier, unfortunately most people are un-necessarily skeptical about them, probably because they don't really get how they work.
I have the Kipon BavEyes reducer for my Fuji and I absolutely love it. IQ is just as good through it as it is without it and it definitely gives you that FF DOF.
Tony_Stark wrote in post #17057476
Only applies to crop sensors as far as I know. I'll never understand the wizardry of Speed Boosters. Cool concept thats for sure!
They're really pretty simple. Think of it as the opposite of a teleconverter. Instead of magnifying the image they do as the name implies, they reduce the focal length using optics. It's more than a concept, it works, and they work very well. I'm really still putting my money on Canon making their own focal reducer for a future M, it would make perfect sense to have the option of using all of your EF lenses in their full glory with full AF and AE control, and given how good Canon's optics are it'll likely be the best reducer on the market.
Wilt wrote in post #17057513
Small thin body, nothing to hang onto except the barrel of a not-so-small lens (especially true of telephoto FL)...wanna buy a battery grip with that, to have place to put your ring finger and pinkie?!
Why does that simply sound like an iPhone with attached supplementary lens?! Anyone else feel like they need to add GPS and a telephone to the camera, and Bluetooth stereo headphone support?! Give it the name pPhone (photoPhone).
'speed boosters' take a lens which is designed for a larger format, shrink the image circle in size for support only of smaller formats (like dedicated video cameras) to accomplish the apparent magic increase in max f/stop. I just cannot imagine taking he Canon100-400 and using a speed booster to use the lens with mirrorless format camera...you need a grip to screw into the tripod mount on the lens, to hold the monster but it still will be front heavy since it has no dSLR body as a counterbalance.
For your first assessment... just no. If you can't see the practicality of having a smaller and lighter camera you're simply being close minded. It reminds me of how people acted when they heard of the 6D's WiFi capability, thinking it's a "gimmick". Give it 5 more years, every camera will have WiFi... why? Because it's incredibly useful. I bet people thought AF was a "gimmick" once too 
As for your second paragraph; I don't know why anyone would buy a mirrorless camera to stick a 100-400L on it... so not sure where that even comes from. But a focal reducer does in fact increase the amount of light for your exposure using the same lens, I know because I've tested it (it's not hard to test). I don't get the advertised full stop, but I do get from 1/2 to 2/3's a stop depending on the lens.
As I (and pretty much anyone else who actually owns a mirrorless camera) have said, it's not the right type of camera for everyone or every use (yet), but many people can see and understand the huge pros of using a smaller and lighter camera with IQ that's just as good or as near as makes no difference to a DSLR, even a FF one. Why everybody is so unwilling to see the advantages they can present is beyond me... if anything I'd say the people stuck thinking DSLR's are the only way to get good pictures are the hipsters