Normal noise level of AF with 18-55mm lens

TinkerPhil wrote:

I now found the source of the excessive noise when focusing. The aperture mechanism.

For example when the shutter speed is set to auto in low light conditions with a small aperture chosen manually, the aperture blades only jump to this setting once I press the focus button. Immediately afterwards, the blades slowly open up the aperture again. Then it's doing this the picture on the LCD screen gives off a weird flickering, I guess from the changing light conditions.

I assume this is to help the AF to find a focus? Is this completely normal or weird? The changing aperture makes a pretty loud noise, compared to the AF.

It's normal, the lens is stopping down to the shooting aperture to focus, then opening again to the brighter 'viewing' aperture.

The slow stepping after AF is so the brightness of the EVF/LCD can adjust without a distracting major sudden jump in brightness - but rather in smaller steps. The amount of stepping you hear will depend on the brightness of the subject (while viewing) and the aperture you set (for actually taking the shot).

Achieving AF with the lens stopped down to taking aperture ensures there is no focus shift - focus plane shifts at different apertures It means you get bang-on focus (far more accurate than with a OVF dSLR), the down-side is the noise and flicker caused by the aperture adjusting between the viewing- taking - viewing aperture.

My £2k GF lenses (on GFX 50S) do exactly the same thing, I except that, as focus is bang-on at the taking aperture.