The description says the lens has a "constant f/4 maximum aperture". The summary says the lens has an "aperture range of f/4 to f/22". Can you tell me what I am not understanding? Thanks.
The f/4 maximum aperture being "constant" means that even when you zoom in to 35mm with the lens, you can still open your aperture up to f/4 (maximum). You do not lose your f/4 capability by zooming in. (If a lens has two maximum aperture numbers, for example f/4-5.6, this means you can open up to f/4 on the wide end, but you lose that stop when you zoom in; at the telephoto end, you can only open up to f/5.6 maximum.)
However, the lens can still run through the rest of the aperture range, all the way to f/22. The description is letting you know more about your max aperture capability, but assuring you that you can choose a smaller aperture/larger f-stop number. (A little difficult to explain! If you need more clarification, please reach out to us at email@example.com.)