I have been using D7200 for almost 4 years now, got the 18-140mm kit lens along, which i have stopped using since an year now, the image quality was pathetic, lacked sharpness throughout the photo, I am looking for a replacement, I mostly shoot Landscapes, couple shoots or portfolios, events. So i need something which covers wide to telephoto range. Maybe a 24-120mm? Is it a good lens? Never got a chance to test it!
So i need something which covers wide to telephoto range.
If you care about getting top-notch image quality from your equipment, trying to do it all with one lens isn't the solution. Get a selection of lenses, and change as appropriate - it's an interchangable lens camera for a reason.
As for which lenses to get, that's where you have to decide which compromises work best for you. The "holy trinity" (at least on full-frame) is the combination of the 14-24, 24-70 and 70-200 f/2.8 lenses, but I'm guessing you probably don't want to spend $6k or more on lenses. If you don't want that, decide whether you're prepared to compromise on:
- Zoom range
- Image quality
The entire point of an interchangeable lens system camera is to allow you to use different lenses that are better or even great at one thing but unsuitable for other things. Fixed lens cameras force you to use a single lens that is mediocre or worse at a lot of things but better at nothing. Insisting on using only a single lens with an interchangeable lens camera is not materially different than using a camera with a permanently attached zoom lens.
The best lenses are all prime lenses. That means a single focal length. No.Zoom.At.All. They're really good when they provide the field of view and other characteristics you need. This is because they can be optimized to do one thing at one focal length. A good flat field 100mm macro lens is different from a good 85mm, 105mm, or 135mm portrait lens. But such specialized lenses are not always very flexible, so you need a lot of them for various different things. Some are pretty good for not much money (e.g. EF 50mm f/1.8 STM @ $120). Others are incredibly good for a boatload of cash (e.g. EF 400mm f/2.8 L IS II @ $10K). Most fall somewhere in between.
Short ratio zoom lenses, that is zoom lenses with a less than 3X difference between their longest and shortest focal length, can also be very good. But the best ones cost a lot. A lens like the Canon EF 24-70mm f/2.8 L II runs around $2K and can match the image quality, if not the maximum aperture, of a $120 EF 50mm f/1.8 STM. It's also built a bit better and can shoot at 24mm (with near the same IQ as a mid-priced 24mm prime) and 70mm and anywhere in between.
When you move outside of the 3x limit is when image quality really starts to noticeably go down. Some 4-5X zoom lenses that fall entirely in the telephoto range can be pretty good. But when you start trying to design a lens that goes from wide angle to telephoto and covers a 5X-10X or more zoom range, that is when it really starts getting difficult to keep it affordable and manageable with regard to size and weight and still provide excellent image quality. You'll usually get better image quality and spend less buying something like an 18-55mm and a 55-250mm pair of zoom lenses than you would get with an 18-200mm 'all-in-one'.
Will you get better image quality with the AF-S 24-120mm f/4G ED VR than with the AF-S DX 18-140mm f/3.5-5.6G ED VR? You probably will. It probably won't be as big of a difference as you seem to expect or want, though. The difference will not be near as much as you'd see using different lenses specifically designed for specific photographic tasks.