Hi Remon550 what lens are you using some lenses are variable aperture ie RF 24-105mm F/4.0-7.1 IS STM lens. As you zoom in the maximum aperture of the lens decreases. Variable aperture lenses are cheaper to make then constant aperture zoom lenses. For ex. RF 15-35mm F/2.8L IS USM which is more expensive due to the wider aperture.
-Demetrius
40D, 5D IV, EF 16-35mm F/2.8L III, EF 24-70mm F/2.8L II, EF 28-135mm F/3.5-5.6 IS USM, EF 50 F/1.8 STM
430EX III-RT & 600EX II-RT
-Demetrius
Bodies: EOS 5D Mark IV
Lenses: EF Trinity, EF 85mm F/1.8 USM
Retired Gear: EOS 40D, EF 50mm F/1.8 STM & EF 70-210mm F/4
Speedlites: 420EX, 470EX-AI, 550EX & 600EX II-RT
