[Nayu]

Hi guys,

I recently purchased a FA 100mm F/2.8 macro lens on eBay. The focusing ring has the same problem as described in this thread:

https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/316268-manu...-macro-wr.html

That is, throughout the 270(?) degrees of rotation for the focusing ring, there would be a few spots where the focusing ring seems to get stiff as if it got stuck and scraped on something for a bit before becoming smooth again. This does not sound like normal operation . It happens with the clamp screw securely on the OFF setting -- I would say it feels like the clamp screw is ON for just those few points. This behavior seems to put extra stress on my K-5's AF motor, causing AF to overshoot(?) sometimes with a nasty physical jerk of the camera in my hands.

However, as it is an old lens (and there is no return policy for that seller except for the eBay money back guarantee), I can't exchange it for a new one. Does anyone have an idea as to what is wrong with the lens? Would it be the internal barrel(?) being off center, resulting in it scraping on the clamp screw once in a while?

There are also marks on some internal element of the lens as if someone opened it up to clean it and left some residue on the element. This is only visible from an angle with a flashlight shining through the lens. Is this cause for concern?

Otherwise, the lens has been exhibiting good optical performance for the limited time I have had with it.

Thanks,

Nayu

[tom1803]

Was the stiff focus ring issue or the dirty element mentioned in the seller's listing on eBay? If not, then I would suggest that you return the lens for a refund.

The stiff focus ring does seem to suggest that "the internal barrel(?) being off center" as you have already assumed. I would guess that the lens has been dropped, front end first, on to a cushioned but firm surface (like a carpeted floor). The impact would have been enough to bend the barrel slightly without showing any external damage.

[grahame]

make sure the clamp is set at "off" when you turn the focus ring.

[Nayu]

Was the stiff focus ring issue or the dirty element mentioned in the seller's listing on eBay? If not, then I would suggest that you return the lens for a refund.

The stiff focus ring does seem to suggest that "the internal barrel(?) being off center" as you have already assumed. I would guess that the lens has been dropped, front end first, on to a cushioned but firm surface (like a carpeted floor). The impact would have been enough to bend the barrel slightly without showing any external damage.

The stiff focus ring issue was not mentioned, and the dirty element wasn't mentioned either. This is the text in the listing:

"I'm switching systems so this is a good opportunity to get a really good deal on a great lens for your APS, K-1, or film Pentax body. It's in good condition both functionally and cosmetically. The glass appears flawless. It comes with a Pentax front cap and an aftermarket back cap."

The seller won't take returns, but there's still the eBay money back guarantee. Should I take that route? Or try to message them first?

make sure the clamp is set at "off" when you turn the focus ring.

I tried turning the focus ring at various clamp settings and it still exhibits the same issue. At "OFF", it is smooth everywhere except for the aforementioned spots where it would get stiff. At "ON", the stiff areas become stiffer along with everywhere else.

[edmundrt]

I don't have any experience with the focussing issue, but my FA100 also has a dirty element - it was very cheap - and it barely affects performance. Pointing it into the light at f2.8 generates more of a halo effect than I would expect from a clear lens, but stopping down quickly cures the problem and by f5.6 it is so sharp it hurts.

[tom1803]

The seller won't take returns, but there's still the eBay money back guarantee. Should I take that route? Or try to message them first?

"No returns" is sort of a standard clause for eBay sellers but in reality, it doesn't mean much because eBay will almost always side with the seller if there's a problem that was not mentioned in the listing.

Best way to approach this is to contact the seller first and POLITELY (don't be angry or aggressive) mention the problems you are having and ask them what can be done about it. If the seller is good, they should offer a full money back on item and postage, plus return postage costing you absolutely nothing except your time. If the seller's response is not satisfactory, then start a "Item not as described" dispute process with eBay, however, you may have to bear the cost of return shipping. If you had to pay import duty, then you need to contact your customs office to get a refund.

The "dirty" element is a common problem with FA 1:2.8 100mm Macro lens. Of 20~30 of these lenses I have serviced, more than half have had this issue in varying degree. Pentax must have used some paint, oil or grease that was prone to evaporation. Curiously it all happens on the same surface, a thin film of oily residue coats the surface of third element that's facing the aperture blades. Usually, the clouding caused is very light and will not have a noticeable image degradation unless you shoot back-lit scenes wide open at f/2.8. It can generally be cleaned off 100% fairly easily. However, whilst taking a lens apart to clean is not "rocket science", I would not recommend it unless you have necessary skills and patience. Even for a pro, servicing a lens always involves risks.

[Nayu]

Best way to approach this is to contact the seller first and POLITELY (don't be angry or aggressive) mention the problems you are having and ask them what can be done about it. If the seller is good, they should offer a full money back on item and postage, plus return postage costing you absolutely nothing except your time.

Thanks for the advice -- I messaged the seller politely and will be returning the lens soon for a full refund.