Hello. Please help. I immediately apologize if my English is not very good. Camera Canon EOS 2000D. Tamron 100-400mm f/4.5-6.3 Di VC USD (A035) Canon EF lens. What is the question, in manual mode, I set the aperture value to the maximum opening (f / 4.2) for example, but when I use the zoom on the lens, the aperture automatically closes, the degree of closing depends on the value of the zoom increase. On the original lens that came with the camera, the same situation. I would be grateful if you tell me if this situation is normal and if something can be done about it. Thanks a lot!
Variable aperture - You can read up on this more if you like, but yes it is normal. To produce zoom cost effectively the by design the widest aperture will depend on the length of the zoom so as you zoom to the long end you loose the 4.5. Fixed aperture zoom will add cost, and isn't available as you start getting longer lenses. Yours is not available in fixed so lets compare some others, look at the 70-200, they have fixed F2.8 and f4, and you end up with a L series and the cost doubles going from 4 to 2.8. For 400mm non zoom, canon makes an f4 but its $7000 , so your can see the wide aperture gets expensive as you get longer.
