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02-21-2010, 06:25 AM   #1
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Ricoh Rikenon XR f50mm 1:1.7 White Ball

Hi pentaxian.

i always wonder what is the purpose of the white ball in between the aperture and focusing ring?

i attached the picture of the lens. I found these white ball only on older type of lens. is it an aide for photographer to tell the focusing mark or something.

this may be a silly question but i'll ask it anyway :P. it's driving me mental for not knowing haha.


02-21-2010, 10:25 AM   #2
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As a film camera n00b myself I didn't know it, either. But from what I've read this knob-thing is for mounting lenses blindly. The lens release button and this knob are aligned when you mount the lens.
With Pentax DSLRs these knobs aren't overly useful as the lens release button is slightly shifted in its position.

Last edited by Egg Salad; 02-21-2010 at 02:05 PM.
02-21-2010, 11:06 AM   #3
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Precisely correct. With older Pentax SLRs, the lens can be mounted blindly by feeling when the lens release button and the "white ball" are lined up. Quick and easy with a little practice.
02-21-2010, 11:09 AM   #4
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That's exactly right. Working in the dark or blindly in the Heat of Battle/Sport watching while exchanging the lens at the same time.
20th century here. FSLR.

02-21-2010, 11:48 AM   #5
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I have heard the term "blind button" used to describe this feature.

02-21-2010, 12:34 PM   #6
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The purpose of the white ball is to drive you nuts when it gets unglued and gets lost!
02-22-2010, 05:53 AM   #7
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Original Poster
guys, awesome pentaxian.

i tested it "blindly" fitting it into my k1000 and yes it helps ei!

Thanks again!

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