A70-210/4 - Optional ring @ rear element?

severalsnakes · 05-06-2015, 05:34 PM

The lens is the SMC Pentax-A 70-210/4

The little ring thing is loose. It moves more or less depending on where the zoom and focus are set, and I'm pretty sure it has fallen down/scooted back far enough once to either interfere with the mirror, or at least block light -- I was able to see the curved black shape of the ring through the viewfinder and the image made was completely dark.

Would it be a terrible idea to leave this ring out? I don't want to damage my $500 camera with a $50 lens. :-/ And it's so loose, I can't believe it's serving any functional purpose.

Last edited by severalsnakes; 05-06-2015 at 06:14 PM.

Erd§ · 05-06-2015, 06:23 PM

While I'm not familiar with that particular lens, is it possible that it is the ring that is meant to screw clockwise over the rear element to keep it in place?

severalsnakes · 05-06-2015, 06:42 PM

Originally posted by Erd§

While I'm not familiar with that particular lens, is it possible that it is the ring that is meant to screw clockwise over the rear element to keep it in place?

Good eye. I also noticed there was a smooth side and a threaded side, so I flipped it over and attempted to "screw" the threaded side down around the rear glass, but there are no threads to match. It just sits there.

**Odinz** · 05-06-2015, 07:28 PM

I just took a look at my A70-210/4 and the rear of it looks exactly like your lens in picture #4. I've had this lens for many years and I have never seen that other ring. Also, the rear element on my lens doesn't move with zoom, focus or macro mode.

Did you just get this lens? Its possible that the lens was serviced and the ring is misplaced from somewhere down inside the lens where it was supposed to hold another element in place, or maybe its not from this lens at all. I've disassembled quite a few lenses, but never this one so I don't know what the optic configuration is like inside.

If the rear element isn't loose, and the lens seems to focus okay, and doesn't rattle when you shake it, I probably wouldn't worry about it, but I'd hang onto the ring just in case..

Steve

severalsnakes · 05-06-2015, 07:45 PM

Originally posted by Odinz

I just took a look at my A70-210/4 and the rear of it looks exactly like your lens in picture #4. I've had this lens for many years and I have never seen that other ring. Also, the rear element on my lens doesn't move with zoom, focus or macro mode.

Did you just get this lens? Its possible that the lens was serviced and the ring is misplaced from somewhere down inside the lens where it was supposed to hold another element in place, or maybe its not from this lens at all. I've disassembled quite a few lenses, but never this one so I don't know what the optic configuration is like inside.

If the rear element isn't loose, and the lens seems to focus okay, and doesn't rattle when you shake it, I probably wouldn't worry about it, but I'd hang onto the ring just in case..

Steve

Thanks for your observations/experience! I bought the lens on Ebay from KEH, so it's anybody's best guess as to what it's been subjected to in the past... I've used it a few times before, but not extensively. When this particular issue popped up, I sat it on the shelf to consider for a while.

But. There's an airshow at the Air Force Base coming up next month and I thought the lens might have just the right focal range to bring along. I remembered this problem and figured I'd better start looking for a solution.

I appreciate any and all input! Thank you!

05-06-2015, 05:34 PM	#1
severalsnakes Veteran Member Join Date: Jan 2013 Location: Kansas City, KS Photos: Gallery Posts: 1,612	A70-210/4 - Optional ring @ rear element? The lens is the SMC Pentax-A 70-210/4 The little ring thing is loose. It moves more or less depending on where the zoom and focus are set, and I'm pretty sure it has fallen down/scooted back far enough once to either interfere with the mirror, or at least block light -- I was able to see the curved black shape of the ring through the viewfinder and the image made was completely dark. Would it be a terrible idea to leave this ring out? I don't want to damage my $500 camera with a $50 lens. :-/ And it's so loose, I can't believe it's serving any functional purpose. Last edited by severalsnakes; 05-06-2015 at 06:14 PM.

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05-06-2015, 06:23 PM	#2
Erd§ Veteran Member Join Date: Aug 2010 Location: SEQ Posts: 323	While I'm not familiar with that particular lens, is it possible that it is the ring that is meant to screw clockwise over the rear element to keep it in place?

05-06-2015, 06:42 PM	#3
severalsnakes Veteran Member Join Date: Jan 2013 Location: Kansas City, KS Photos: Gallery Posts: 1,612 Original Poster	Originally posted by Erd§ While I'm not familiar with that particular lens, is it possible that it is the ring that is meant to screw clockwise over the rear element to keep it in place? Good eye. I also noticed there was a smooth side and a threaded side, so I flipped it over and attempted to "screw" the threaded side down around the rear glass, but there are no threads to match. It just sits there.

05-06-2015, 07:28 PM	#4
Odinz Loyal Site Supporter Join Date: Jan 2008 Location: Virginia, USA Photos: Albums Posts: 259	I just took a look at my A70-210/4 and the rear of it looks exactly like your lens in picture #4. I've had this lens for many years and I have never seen that other ring. Also, the rear element on my lens doesn't move with zoom, focus or macro mode. Did you just get this lens? Its possible that the lens was serviced and the ring is misplaced from somewhere down inside the lens where it was supposed to hold another element in place, or maybe its not from this lens at all. I've disassembled quite a few lenses, but never this one so I don't know what the optic configuration is like inside. If the rear element isn't loose, and the lens seems to focus okay, and doesn't rattle when you shake it, I probably wouldn't worry about it, but I'd hang onto the ring just in case.. Steve

05-06-2015, 07:45 PM	#5
severalsnakes Veteran Member Join Date: Jan 2013 Location: Kansas City, KS Photos: Gallery Posts: 1,612 Original Poster	Originally posted by Odinz I just took a look at my A70-210/4 and the rear of it looks exactly like your lens in picture #4. I've had this lens for many years and I have never seen that other ring. Also, the rear element on my lens doesn't move with zoom, focus or macro mode. Did you just get this lens? Its possible that the lens was serviced and the ring is misplaced from somewhere down inside the lens where it was supposed to hold another element in place, or maybe its not from this lens at all. I've disassembled quite a few lenses, but never this one so I don't know what the optic configuration is like inside. If the rear element isn't loose, and the lens seems to focus okay, and doesn't rattle when you shake it, I probably wouldn't worry about it, but I'd hang onto the ring just in case.. Steve Thanks for your observations/experience! I bought the lens on Ebay from KEH, so it's anybody's best guess as to what it's been subjected to in the past... I've used it a few times before, but not extensively. When this particular issue popped up, I sat it on the shelf to consider for a while. But. There's an airshow at the Air Force Base coming up next month and I thought the lens might have just the right focal range to bring along. I remembered this problem and figured I'd better start looking for a solution. I appreciate any and all input! Thank you!