Quick question about a summicron 35

[Rhodes]

The various apertures of the blades (the f-stops) are different from lens to lens? I compared the apertures of my elmar with my summaron and the latter has smaller aperture for the same f-stop.
I am asking because, the summicron is a bit stiff and I post here a few time ago how to dismantle to lub,etc and during my try out, I dismantle a part of the lens that when I put it back and screw it tight, the blades could no open. I loose it up and know it's working fine, but I do not no if the f stops are correct.

I made a mistake about the name, sorry!

 

[umcelinho]

you mean same aperture in absolute size of the iris in another lens in the same focal range? i think it doesn't change from lens to lens, from what i've tested here with mine. F16, f5.6 and f2 all look to have the same iris size (canon 35/2, nokton 35/1.2, summicron 35 v4). but when comparing to a different focal length, say, 21mm or 50mm, the size of the iris is different.

 

[icebear]

Hi Rhodes,

the aperture is the ratio between the front lens diameter and the total length of the sytem, if I'm not mistaken. If you have different length of lenses f=8 in one lens will have a different size opening in mm than f=8 in another lens. The ratio might be the same, so the same amount of light will travel through the lens systems but the opening diameter is not exactely the same.

To test the lens if the apertures are still fully functional, you'll have to take pictures of time/aperture combinations that result in the same EV (exposure value / amount of light). If you measure e.g. 1/125 at f=5.6 , you try also 1/250 at f=4, 1/500 at 2.8 , 1/1000 at f=2 , etc. If everything still works fine, all exposures should be identical.

And about dismanteling and self CLA (cleaning lube adjustment)... I don't know your skills but usally that's a pro job. I would never open up one of my lenses myself and I would rate myself as pretty handy otherwise. If it's a cheap buy and 100 bucks for CLA is more than the lens is worth than just try your luck, have fun😉.

 

[Rhodes]

Thank you for the replies. I thought that to access the helicoidal part to re-lube was like the elmar, but it is not. The lens is only hard to move when un-locking the infinity lock then it is ok. But I only notice this when the lens is in the bessa R. In my IIIc, it does not apper stiff.