>>3288523Unless you own BOTH full frame and crop sensor cameras simultaneously, just learn to use APS-C lenses. There is absolutely no reason for people who only own crop sensor cameras to keep trying to force the "FF equivalencies" camera shop meme.
1. A moderately wide to moderately telephoto "standard zoom" is going to be something like 18-50mm or 16-50mm or 18-55mm, something in that range - for a little bit of extended telephoto range, 16-85mm gives you that edge, usually at the cost of being physically larger.
2. True normal is 27mm, but anything from about 23mm to 30mm will be about as effective for "walkaround" type photography, allowing you to zoom with your feet to make up for the difference.
3. Anywhere from 35-70mm is a good general focal length range for portraits. 50mm would be more of a classic focal length. 90mm crops in pretty tight, but works great if you have enough room to back up. 23mm is good for wider perspective, environmental portraits.
3. A super magnification zoom is going to be in the 18-135mm or 18-200mm range, something like that. Such lenses go from relatively wide to borderline long enough for wildlife, usually at the cost of image quality.
4. 300mm is long enough for most wildlife and casual birding. 400mm f/5.6 is better for birding, but also is about as long as you'll be able to use effectively, given the limits of a crop sensor's high ISO noise (unless you're using a super modern camera like the D500), the shutter speed required to freeze subject motion and camera shake, and the lighting of when you'll find most wildlife.
5. 10-20mm is an ultrawide focal length range. Any extra range at the long end will make the lens a bit more useful. 8mm would be typical for a fisheye.
6. Additionally, aside from its effect on exposure, f-stops of f/2 and lower only should be considered competent in terms of subject isolation.
