I have been carrying this fairly small A7rii with the tiny 35mm 2.8 lens for a couple weeks and here is what I can say. It is a superb set-up with fast auto-focus and the files are outstanding. This was my main reason for trying this as a walk around. You see I am lusting after the latest version of the X100, the X100F. I currently own the T and love it but I often find that I tend to crop in post and would love to have a bit more file size plus I already own the Sony A7rii which I use for nearly all other photography.
But the fact is I am probably only delaying the inevitable as I will go back to my X100T soon enough and buy the X100F somewhere down the line when the price drops.
Right, I guess I should get to the why. It's simple really, the experience. The A7rii is a powerhouse. Tilt screen, stabilized sensor, beautiful viewfinder, dynamic range from the gods and files that can be blown up to skyscraper visuals. And none of that matters if I am not inclined to grab it every time I go somewhere or if the experience of making the images is just a tad less fluid because those two things combine to taking less shots and missing more moments. If you are a pro trying to capture a variety of images, changing setting is important all the time. You want a slower shutter, a different aperture, etc. On the Sony this means looking at a digital display either through the viewfinder or the screen on the back. On the Fuji, its right on the dial, making for a fast natural experience. Those film rangefinders that this camera is modeled after must have hit a magic formula.
The weight and size is a bit of a factor as well but I do believe ease of use it the killer app for me. Here are some images captured with both cameras. The first four are X100T and last 3 are Sony A7rii.
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