35-70/3.5 AIS Nikkor

[dynachrome]

I took delivery today of a 35-70/3.5 AIS lens. When the lens is not attached to a camera and I look through it,, with the aperture set to f/3.5, the view is round at the 70mm setting. As I turn the zoom ring in the direction of the 35mm setting, I see the seven aperture blades. Is this normal?

 

[Jesper]

At aperture 3.5 at 70mm you will have a physical opening of 20mm and at 35mm the opening should be 10mm

 

[fdonadio]

At aperture 3.5 at 70mm you will have a physical opening of 20mm and at 35mm the opening should be 10mm

I had never thought about that. So it means the lens could be one stop faster at the shortest focal length, if the light path would allow for it.

 

[jimjm]

Mine does the same. Never noticed it before, but it's probably normal.

 

[Huss]

How does it work with the lens on your camera?

 

[flavio81]

I took delivery today of a 35-70/3.5 AIS lens. When the lens is not attached to a camera and I look through it,, with the aperture set to f/3.5, the view is round at the 70mm setting. As I turn the zoom ring in the direction of the 35mm setting, I see the seven aperture blades. Is this normal?

Yes, this is normal on constant-aperture zoom lenses.

At the short end the diaphragm automatically stops down to maintain the constant f3.5 speed.