60D-Aperture problem when shooting video

[LegacyVideo]

I have a 60D with an 18-135 mm 3.5 lens. I've set the camera for manual exposure. When I have the lens full wide, the aperture reads 3.5, when I zoom in tighter, the aperture changes to 4, 4.5, etc. Seems like there's something automatic going on that I don't understand. If I'm on manual exposure, shouldn' the aperture remain at 3.5 until I change it? Many thanks for any ideas.

[diverhank · Accepted solution]

I wouldn't call it a problem...your lens has variable maximum apertures depending on focal length - f/3.5 at the wide end and f/5.6 at the tele end.  When you set the f-stop to f/3.5 at the wide end, it was allowed but when you zoom in, 3.5 is no longer attained, the camera simply is smart enough to set the max available aperture for you even in manual mode.

[LegacyVideo]

Thank you for the information!