I've been shooting so much that I haven't had much time to write.
I received my Olympus 8mm fisheye lens and I'm quite pleased. I'm extremely happy with it, but it takes some acclimation to its ultra-wide angle. I'm working on a specific report of my experiences.
July 5th, I got a special deal on the Nikon D7200 and Sigma 18-35mm f/1.8 lens. I've been shooting so much that I haven't even had a chance to write more than this about the combination. I have plenty to say, especially since this is the first real attempt to switch brands--or at least, add to my arsenal of tools.
I haven't used any Nikon equipment since film SLRs. It's taking some time to get good work done. Their whole design work, electronic and physical, lacks clear thinking. I appreciate that they have a status display, but if should be interactive, instead of just being frustratingly informative.
Something interesting and frustrating was learning how to switch from the factory setting of auto focus scatter pattern with 51 focus points to 1 focus point. There is a button located within the AF/MF switch to the left of the lens mount. Is it labeled? No. You hold it and rotate the rear dial to change patterns.
In any case, I am finding many new user problems that I didn't find with the Pentax K-50.
My main reason for buying the D7200 was its low(er) light performance. I first took it out at 11/23 at night. It was a frustrating experience, especially since AF supposedly works to -3 EV--what was standard with the Panasonic GH3 way back when it was introduced. Half of the photos I tried to take just would not happen. Subsequently, I took the Olympus E-M1 and Panasonic GH4 out at similar times. The E-M1 struggled a bit but the GH4 didn't hesitate. How good is the image quality of a camera body that won't take an image?
My first impression of the Sigma 18-35mm f/1.8 is that it's small, light, and too short in its focal length range, especially compared to my Olympus 14-35mm f/2.0. It's also not weather-sealed which could be a major problem. I didn't pay full price for it, which helps alleviate some of the shortcomings. If you think it's not small or light, take a look at the Tamron 15-30mm f/2.8 lens.
I'll take some time to write about these experiences in detail.