I recently switched from my Nikon D300 workhorse to the full-frame Nikon D750, and had the opportunity to try the D750 out on a trip to Kazan, which is the capital of the Republic of Tatarstan in Russia. When released in 2007, the D300 was a stellar, tough-as-nails DX-fomat camera that was great at action, wildlife and general photography. The D300 was my companion on trips all over Europe and North America. It was impeccably reliable, and I appreciated the extra reach of the DX sensor.
However, I finally decided that the price was right to jump to a full-frame sensor (FX), and picked up the D750. I first started in photography with a 35mm film SLR, and always had the itch to get back to an FX format. The two primary motivations for the switch were much higher resolution (24.3MP vs. 12MP for the D300) and the well-known, superb low-light capabilities of the D750. I wanted a camera that was good at both shooting landscapes and, say, low-light interiors, while still having many of the advantages of the D300 in terms of shooting action and other types of photography as well as having weather-sealing. Like the D300, the ergonomics and general layout of Nikon D750 DSLR camera are also great.
However, I did consider moving to the mirrorless Sony A7III. Much of my shooting is travel photography, and the light weight of the Sony system was seductive. The D300 felt like a brick around my shoulder. I decided against the Sony for three reasons.
One was the price. Aside from the body which was about $2,000, the lenses were very expensive and limited in selection. For example, the Sony FE 24-105mm f/4 lens was $1,300. By comparison, I could (and did) get a superb Sigma 24-105mm f/4 Art Nikon-mount lens for $899. The lens selection for Sony will improve in the near future, though, as other lens manufacturers like Tamron and Sigma begin offering lenses for the Sony mount.
Second, in my opinion, the ergonomics of the Sony A7III are not great compared to the Nikon. The Sony is very angular, and doesn’t have the natural, comfortable feel of the Nikon camera. Nikon spoiled me in this regard.
Finally, I wasn’t convinced on the longevity of the Sony. For example, Imaging Resource conducted an infamous water torture test on a selection of DSLRs including the Sony A7RIII and Nikon D850. In a nutshell, the environmental sealing of the Sony left a lot to be desired compared to other cameras. I’ve been caught in some nasty weather while traveling or hiking with my old D300, and never had to worry about it.
Many professional photographers have switched to the Sony system, but, for me, its advantages were not enough to dump Nikon. If I switch to mirrorless in the future, it will likely be to the Nikon mirrorless Z6 camera. The new Z6 was announced when I pulled the trigger on the D750. Why would I buy a D750 over the Z6? Mainly because I didn't want to wait until Nikon smoothed out the inevitable kinks of its new mirrorless system. I tend not to be an early adopter of technology, which is one reason I stuck with the D300 for so long.
The next step up from the D750 is the Nikon D850. The D850 is a beast of a camera with stellar image quality. However, it’s also a little overkill for my purposes. It was $3,300 and weighs one-third more than the D750, which I snagged for $1,600. The differences in capabilities and image quality between the D850 and D750 were not sufficient to provide a good return on investment from purchasing the D850, in my opinion. Like the D850, the D750 is weather-sealed. In the end, I would rather spend the difference in price on lenses.
For travel, I paired the Nikon D750 with the Sigma 24-105mm f/4.0 Art lens. The Sigma lens is known for its sharpness, particularly at wide angles, and it is a very versatile, general purpose lens. This combo was actually a recommendation made by Tony Northrup, and it performed extremely well on my trip to Russia. Overall, I am very happy with the D750. Even though some may consider it old tech, it’s still a robust, highly capable DSLR that will satisfy my needs for the next several years.