Nikkor 50mm 1.4 AI-S, aperture visible at wide open.

[zanxion72]

I have just noticed that the aperture on my Nikkor 50mm 1.4 AI-S stops down by just a bit making the blades just visible at f/1.4. It is just by a millimeter or less. Is that normal? I don't have another Nikkor 50mm 1.4 to compare.

 

[shutterfinger]

50/1.4=35.7. Looking through the front of the lens is the aperture opening 35.7mm? Aperture=lens focal length divided by entrance pupil. Entrance pupil is the diameter of the aperture opening as viewed through the front of the lens. Divide the focal length by the f number to get the diameter that the entrance pupil should be. Measure at the center of the lens.

 

[zanxion72]

I could not help it and opened the lens from the front. It is just easy. I noticed that the aperture governor ring had slipped as those red marks on the black weren't aligned with these on the screws. I loosened the screws a bit, pushed the black metal by just as far as to bring the blades sharply aligned to the widest opening but no further. And that was it. That lens had either been opened, or that ring had just slipped by a bit.