[Ketsuppi11]

Hi,

I bought a K135mm/2.5 that looks to be in excellent condition. Everything seems to work perfectly, except it doesn't focus to infinity.
I can't see any faults inside or outside the lens. Any ideas what could cause this?
I have tested the lens with KP and on a film camera and it always behaves the same way.

Thanks

[stevebrot]

K135mm/2.5 doesn't focus to infinity

When at its infinity stop, where does it focus, distance-wise?


Steve

[TwoUptons]

Sometimes this just happens... it could have been like that since new, and it’s possible prior owners never noticed.

In many cases, there’s a way to adjust where the lens focuses at the stop.

I adjusted my K45-125 zoom. It wouldn’t focus past ~15m. Now it’s fine. I had to pull back the lens rubber grip, loosen some set screws, move the lens, and repeat until correct. It took an hour or so of pointing the camera down the street one night, but it was totally worth it.

-Eric

[Ketsuppi11]

When at its infinity stop, where does it focus, distance-wise?


Steve

it focuses up to 15m or so. Focusing ring turns normally all the way to the infinity mark.

[stevebrot]

it focuses up to 15m or so. Focusing ring turns normally all the way to the infinity mark.

Well, that is not right.

You may be able to secure a return for refund or that failing, adjust the focus ring to a more acceptable position as described above. It may be that a previous owner found the minimum focus distance (1.5m) inadequate for their needs and nudged the ring to suit.


Steve

[Ketsuppi11]

Well, that is not right.

You may be able to secure a return for refund or that failing, adjust the focus ring to a more acceptable position as described above. It may be that a previous owner found the minimum focus distance (1.5m) inadequate for their needs and nudged the ring to suit.


Steve

The minimum focus distance is still 1.5m. There's no chance for refund but I got a good package deal so I won't take a big loss on this lens but I have been after it for a while so it would be nice to get it t work properly.

---------- Post added 13-10-19 at 21:10 ----------

Sometimes this just happens... it could have been like that since new, and it’s possible prior owners never noticed.

In many cases, there’s a way to adjust where the lens focuses at the stop.

I adjusted my K45-125 zoom. It wouldn’t focus past ~15m. Now it’s fine. I had to pull back the lens rubber grip, loosen some set screws, move the lens, and repeat until correct. It took an hour or so of pointing the camera down the street one night, but it was totally worth it.

-Eric

I would like to try that. Could you give me a bit more instructions how you did it?
Thanks!

[Not a Number]

I would like to try that. Could you give me a bit more instructions how you did it?
Thanks!

Adjusting the infinity focus on prime lenses is pretty much straight-forward. The basic procedure should be similar with K-series lenses. Remove the name/trim ring. Remove the 3 or more screws holding the filter ring. Remove the three screws holding the outer barrel to the front helical assembly. With the lens mounted on a camera body focus on a distant object by turning the front helical with your fingers. Replace the outer barrel aligning the infinity mark (centered) to the focus mark. Replace screws - don't tighten them down completely (or only one or two) as you may need to fine tune. Check infinity focus and minimum focus. Adjust if needed. Tighten the screws and re-install the other parts.

Check the lens disassembly database for tips on K-series primes
Pentax Lens Disassembly Database - PentaxForums.com

[stevebrot]

Adjusting the infinity focus on prime lenses is pretty much straight-forward. The basic procedure should be similar with K-series lenses. Remove the name/trim ring. Remove the 3 or more screws holding the filter ring. Remove the three screws holding the outer barrel to the front helical assembly. With the lens mounted on a camera body focus on a distant object by turning the front helical with your fingers. Replace the outer barrel aligning the infinity mark (centered) to the focus mark. Replace screws - don't tighten them down completely (or only one or two) as you may need to fine tune. Check infinity focus and minimum focus. Adjust if needed. Tighten the screws and re-install the other parts.

Check the lens disassembly database for tips on K-series primes
Pentax Lens Disassembly Database - PentaxForums.com

And, as always, any cross-head screws one might find are not Phillips-head. They are JIS cross-head and have both different depth and different angle. Use of a Phillips screwdriver runs the risk of stripping the screw head, though it has been done with no harm.* I might also caution that care should be used when removing the focus grip. It may be brittle with age.


Steve

* I have done so, but now that I own a selection of JIS drivers, the difference in fit is obvious.

[HoutHans]

Thanks for this, even when my K135 focusses to infinity, I find that it wobbles a bit. My guess is that this will allow me to sort that out as well.

[Not a Number]

And, as always, any cross-head screws one might find are not Phillips-head. They are JIS cross-head and have both different depth and different angle.

Thanks, I meant to add this caution but my attention got diverted elsewhere. Very wise advice indeed.

I might also caution that care should be used when removing the focus grip. It may be brittle with age.

Another good point. On telephoto primes the screws holding the outer focusing barrel to the front helical barrel are sometimes under the "rubber" grip which needs to be rolled/pulled away/off.

[jlstrawman]

And, as always, any cross-head screws one might find are not Phillips-head. They are JIS cross-head and have both different depth and different angle. Use of a Phillips screwdriver runs the risk of stripping the screw head, though it has been done with no harm.* I might also caution that care should be used when removing the focus grip. It may be brittle with age.


Steve

* I have done so, but now that I own a selection of JIS drivers, the difference in fit is obvious.

In my research, I have seen mention of at least 7 different screwdriver tips sizes. I suspect the larger numbers denote
screwdrivers for Japanese motorcycle repair, or similar. What sizes would an infrequent user really need to make adjustments
like mentioned in this thread?

Thanks.

[Just1MoreDave]

The front barrel on the K135/2.5 unscrews* and the front three elements all come off in that barrel. That should get you very close to the three screws that hold the focus ring onto the mechanism. Since it's a K lens, I wouldn't be surprised to see a large washer acting as a dust cover for the focus helix, which might just fall out if you invert the lens. Adjusting infinity should be pretty similar to any of the lens repair articles on Takumar primes like the 50/1.4 - loosen the screws, change the position of the focus ring, retighten, put the front back on and see if you get to infinity. Be careful with the very fine threads on the front barrel, they look easy to crossthread.

I know I have posted pictures of the lens with the front unscrewed, but can never find anything since it became Google Photos.

*without tools, just grab it and twist

[Mercifulfate]

Sometimes this just happens... it could have been like that since new, and it’s possible prior owners never noticed.

In many cases, there’s a way to adjust where the lens focuses at the stop.

I adjusted my K45-125 zoom. It wouldn’t focus past ~15m. Now it’s fine. I had to pull back the lens rubber grip, loosen some set screws, move the lens, and repeat until correct. It took an hour or so of pointing the camera down the street one night, but it was totally worth it.

-Eric

This is your easy answer right here.

[stevebrot]

What sizes would an infrequent user really need to make adjustments
like mentioned in this thread?

I am partial to Moody for small-size drivers and IFIXIT sells a four piece set of Moody small head JIS drivers (Moody #58-0405) for about $20 USD. These drivers have hardened steel shafts/point and safety handle and lifetime guaranty. These drivers are long-shaft, though similar sets from Moody short shafts are available through other vendors for a bit more money.

The sizes are:

#000
#00
#0
#1

IFIXIT | JIS Driver Set

These sizes will cover most of what you might encounter on Pentax 35mm and APS-C cameras and lenses. Medium format and long lenses might require a couple of sizes larger up.


Steve