Olympus S Zuiko 35-70/3,5-4,5 zoom

[Eugen Mezei]

I got this lens for my OM10. Now I have a question regarding the size of the apperture hole.
When I am at the 70 mm position than the apperture opens completly. At the 35 mm end the apperture blades become visible. I don't know if this is normal. I would like to hear the opinion of somebody else owning this zoom and if his acts exactly like mine.

Yes, I know the definition of the apperture number. k=f/d
So I will get 3,5=35mm/10mm and 4,5=70mm/15,5mm what clearly states 5 mm difference of the apperture hole at the two ends of the zooming focal lenght.

Still, I wish somebody could confirm me if my lens is not faulty. (I got it used from KEH and we all know their warranty politics.) I wish to shoot some slide in my OM10 so I hope this lens would not incorrectly expose.


Also it would be nice to know how the CLOSE FOCUS setting on this lens works.


Greetings,

Eugen

[aoleg]

I don't have experience with this particular version of Zuiko 35-70, but my Zuiko 35-70/3.6 behaves exactly the same way. For the f/3.6 version, this is normal behavior; Olympus did it to maintain the fixed maximum aperture of f/3.6 throughout the range. What's particularly neat about the design is that the blades stay OPEN until you actually shoot the lens (or push the DoF preview button on the lens), so at 35mm you focus at something like f/2.8 (Yes, the lens seems to be a f/2.8-3.6).

Note that Contax Vario-Sonnar 35-70/3.4 behaves exactly the same.