Rattle in pentax 67 55mm from ebay

[brian_carter2]

<p>I recently received a late model 55mm "67" lens from ebay that was sold as like new, etc.<br>

Upon inspection I noticed the regular bearing like rattles that are common (in my limited experience) to 67 lenses (though this one may have more bearing rattle than most). But I also hear a bit of a thunk when the lens is flipped over. The thunk originates from the rear element group that moves in-out when the focus is changed. I estimate total play at around .5mm to .75mm. There does not seem to be any side to side play. There does not seem to be any free play at the front of the lens, suggesting there would be some optical impact from the motion.<br>

Obviously, I am concerned about alignment and optical quality and wondering if anyone has had experience with this. Does your 55mm make this thunk? Any looseness back there? The lens is in otherwise great condition.<br>

I did get a decent price on it but am trying to choose between the 45mm and the 55mm and don't see keeping both.<br>

I did some searches and found someone else with a similar problem:<br>

http://www.photo.net/medium-format-photography-forum/00Evp6<br>

General questions:<br>

How serious is it? Optical impact? What typically causes it? Will it get worse?</p>

<p>Thank you!</p>

 

[ronald_moravec1]

<p>.5 mm is enough to throw the lens out of wack.</p>

[d_purdy]

<p>My 55 does have some motion when I shake it on the axis of the front and rear elements.. like a salt shaker. Funny I never noticed it before. That is the only motion it has. My lens is fine.</p>

[brian_carter2]

<p>Thanks for checking, Dennis, Is it more like a thunk or more like ball bearings/rice? I thought the ball bearings/rice noise was normal. It isn't quite as loud when the lens is stopped down and on manual.<br>

I hear the ball bearings/rice sounds from the 45, 55 and 105.. the 55 is the only one with a thunk.<br>

If I hold the lens facing up, I can feel the play on the bottom group by pushing up on the collar.</p>

 

[razondetre]

<p>Tighten the retaining ring holding the glass in place. Those rings loosen on lots of lenses and the glass group moves around. Just make sure it flumps back down smoothly into its seat and tighten the retaining ring. </p>

[brian_carter2]

<p>Thank you, Josesph. Hmmm.. The outer rings seems snug when I try and tighten them with rubber gloved fingers.<br>

When the focus is adjusted, this entire rear optic assembly retracts into the lens. It is that entire assembly that seems slightly loose, not an individual element. And it doesn't seem to wiggle, more of in-out looseness. I would guess that something down near the base of that assembly (deeper in the lens) is the issue. As I look in with a flashlight, that element group sits on a wider plate within the lens and it is the whole assembly that has the potential issue. If I had a good internal diagram, I could understand the mechanics, which I am curious about (but sufficiently fearful of!). It would be nice to know whether this is resolved with an adjustment or inexpensive repair, etc.<br>

The seller says he has owned the lens since it was new and it takes great pics. I would like to believe him, of course, but have no way of knowing. Maybe the lens was dropped in a way that did not produce external damage, I don't know.<br>

I wish I could 'trigger' the slop while looking through the viewfinder but that would be difficult. And the 67 finder is rather dark. I guess my concern is focus shift during MLU or shutter trip.</p>

<p> </p>

[rod_sainty2]

<p>Brian, I'm going to suggest that there is nothing seriously wrong with your lens. I've never owned the 55mm, but have owned the 45mm, 75mm shift, 90mm, 165mm and 300mm. In these and, I think all, Pentax single focal length (67 and 35mm) lenses, the entire, not just the rear, lens assembly moves as a single entity towards and away from the film plane as focus is adjusted. Yes, when you focus closer, the rear of the lens moves forwards. But the front of the lens also moves forward by the same amount. So, the slight movement that you can detect when you hold the lens facing up and push on the rear collar should move the entire lens assembly upwards. This will not affect sharpness, and could be easily fixed if you wanted. However, if you can confirm that the rear lens element does move 0.5mm to 0.75mm independently to the front element, then, obviously, sharpness would be compromised. Nevertheless, I think that this would also be an inexpensive adjustment by a competent technician.</p>

[chuck_pere]

<p>I've also just picked up a used late model (67 type) 55mm that sounds the same. First it has that "rice" like rattle when you rotate the lens back and forth. My other lenses a 105 and 200 don't have this same rattle. But from what other say it might be common. It also stops when the lens is stopped down. Then you only hear a small clicking rattle. Shaking the lens back and forth (like a salt shaker) you hear the clunking noise. I can also hear this noise when pressing on the rear element group but only when the front of the lens is slightly elevated. The rear element looseness seems to coincide with a small click that occurs as you rotate the lens front to rear. When the the front is below the rear there is no play in the rear group. When it is above the rear the rear group has some very slight play and you hear a clunk when pressing on it.<br>

The lens seems to function fine on the camera. Couples to the meter properly (Pentax 6711) as checked with other lenses. Focus is OK. I've run some film through it and the negatives looked fine. Included some crude sharpness tests of newspapers, bookcase, tree limbs. Now that I've seen the problem closer I'll need to try more checks. Maybe setup a subject at a distance and shoot with the camera pointed slightly upward and slightly downward without changing focus. See if I can see any difference. Like yours mine does not show any type of external damage. In fact it is in mint shape and came with the original box. I could have returned it but didn't because I got a good deal and when buying used equipment sometimes the devil you know is best.</p>