lens - Universal solution for wide focus length DSLR camera in 2017

Please help me to find the right solution for my needs. I'm looking for a high quality camera, it should be modern, capable to record high-quality videos in FullHD (4K not needed at all). In the question of photography I find myself taking low light photos more often than anything else. But I need a universal lens with focal length range ~20 to ~200 (+/-) and a camera that suit this lens perfectly well. For now I consider Pentax KP and Pentax SMC DA 18 - 270 mm f/3.5 - 6.3 ED SDM, but I'm not sure it's the best what I can get under my budget (US$2500).

Priorities:

• FullHD still video recording (natural indoor light, w/o any additional lights set)


• Daytime photography macro - portraits - telephoto;


• Optionally I would be happy to be able to take acceptable (or better quality) shots at evenings;

I would really appreciate your help as well as if you point out weak and strong sides of my current pick. Will I've better results if I stick with a superzoom camera, like Sony DSC-RX10M4 or Panasonic FZ2500?

It's very important to have only one lens so please do not suggest me two use 2 different lenses.

Answer

The solution you want does not exist in 2017.

There are no 20-200mm f/1.8 lenses for full frame sized or APS-C cameras. There are not even any 20-200mm f/2.8 lenses for FF or APS-C cameras. f/2.8 is pretty much the default minimum aperture for shooting stills in very low light.

The reason there are no such lenses are that they would be far too heavy, much too large, and way too expensive to be practical while still delivering much poorer optical image quality than much smaller, lighter, and cheaper lenses can deliver.

If you really want to go there, you can get a broadcast quality video lens such as the Canon DigiSuper 100AF that projects an image circle large enough for a 2/3" broadcast camera with a 9.3-930mm focal length. It gives an equivalent field of view on such a cameras as that of a 36-3656mm lens on a FF camera. It only weighs 60 pounds and costs a bit more than $200,000. And that is for a 9.59x5.39mm video sensor with a 3.9X crop factor.