In article , Bruce
wrote:

So I have this Tamron 28-300 (which is 18-200 on a FX body, right?
Sorry if I get that backwards) which is a fine enough lens, but it
goes from f3.5 - f6.3. It's not a huge lens by any stretch.

What I am wonder is why such a lens can't be made that is either 2.8
straight through or has an at least lower f-stop throughout (say 2.8
- 4).

It simply isn't possible to make a good, wide aperture 11X zoom lens
at an affordable price. You can thank the laws of physics for that.

that's why they're not wide aperture, but rather f/4-5.6 or so.

11X zoom lenses are best avoided. Period.

nonsense.