Tight fitting Pentax-M 50mm f 1.7?

ZombieArmy · 11-27-2017, 04:00 PM

Hi. I just got a Pentax M 50mm 1.7 on ebay. The lens is in immaculate condition but it seems to take a lot of force to get it on my k-01. To the point where I think it scuffed the mount a little bit.

This doesn't happen with my 200mm which is also an M lens, what could be the cause?

photoptimist · 11-27-2017, 04:04 PM

Maybe a warped mount ring or bent bayonet tabs?

I'd sight along the ring and tabs carefully to see if you can find the offending bend.

A wee bit'o filing (with ALL lens opening covered in masking tape) might reduce the tightness if you can identify the source.

**twilhelm** · 11-27-2017, 04:09 PM

Sounds like it was dropped on the mount. Do a close inspection side be side comparison with your 200. You’ll find the problem spot.

Not a Number · 11-27-2017, 04:09 PM

The location of the scuff marks should provide a clue where a possible problem could be.

It may just be the luck of the draw - the mount on the lens as at towards the extreme in one direction of the specified tolerance and the mount in the other direction. Both are still within specifications but combined things work out to being stiff or tight.

ZombieArmy · 11-27-2017, 04:35 PM

I can not perceive any warping on the mount. The pentax 200mm will go on and turn with no effort, while when i put the 50mm on it will not move at all with the same amount of force.

pschlute · 11-27-2017, 04:44 PM

The M50 mm are cheap enough on ebay. Get another and sell yours for parts

ZombieArmy · 11-27-2017, 04:50 PM

Originally posted by pschlute

The M50 mm are cheap enough on ebay. Get another and sell yours for parts

Sorry but we're not all in a situation where we can throw away money.

pschlute · 11-27-2017, 04:53 PM - **1 Like**

Originally posted by ZombieArmy

Sorry but we're not all in a situation where we can throw away money

Well then throw away the lens. Or would you prefer to keep damaging the camera mount?

ZombieArmy · 11-27-2017, 04:54 PM

Originally posted by pschlute

Well then throw away the lens. Or would you prefer to keep damaging the camera mount?

You could leave my thread.

photoptimist · 11-27-2017, 04:57 PM

Originally posted by ZombieArmy

You could leave my thread.

Honestly, I think he's giving you good advice. The camera is worth more than the lens.

ZombieArmy · 11-27-2017, 04:59 PM

Originally posted by photoptimist

Honestly, I think he's giving you good advice. The camera is worth more than the lens.

I thought it was common sense to stop using a lens that requires 6x the force to mount onto the camera. The thread is for causes and possible solutions, not to tell me to call it all a loss "because it doesn't cost much".

**twilhelm** · 11-27-2017, 05:24 PM

Unfortunately that is part of the risk of ebay and buying old equipment. People will put things on for sale which look good but have a defect. I've lost a few and I've won a few. I bought a Sigma 28 which looked new, but was so badly de-centered it was not usable. Then I had a guy ask if I wanted a horrible looking lens in K mount with a bent filter ring and he threw it in for free. I got one of my favorite lenses, a K 55 1.8 which looks terrible, but has perfect glass.

**jatrax** · 11-27-2017, 05:26 PM

Originally posted by ZombieArmy

I thought it was common sense to stop using a lens that requires 6x the force to mount onto the camera. The thread is for causes and possible solutions, not to tell me to call it all a loss "because it doesn't cost much".

You already got the most probable cause, the mount is bent. Carefully examine where it is rubbing and you should find the issue. I sorta agree with the other poster about tossing it out, an M 50 f/1.7 should be what $25-$30? Not worth damaging your camera. But in your case you bought it on ebay so tell the seller it is defective and you want a return.

If you don't like those options then get out a file as @photoptimist says.

Or just keep using it and scratch up your camera mount. Leaving this thread now.............

stevebrot · 11-27-2017, 05:29 PM

It should mount easy and smooth unless the lens mount was poorly machined or has been damaged. As noted above, are there any signs of unusual wear, scratches, or damage to the mount tangs or mount face? Is the aperture actuator properly aligned and fully operable with a flick of the finger with no roughness or hesitation? (A bent/misaligned actuator is a dangerous thing.)

You are right to be exercising full caution with the lens on your camera. A defective Russian fisheye permanently damaged the aperture actuator of one of my film bodies. You may want to be talking to the seller.

Steve

ZombieArmy · 11-27-2017, 05:34 PM

Originally posted by stevebrot

It should mount easy and smooth unless the lens mount was poorly machined or has been damaged. As noted above, are there any signs of unusual wear, scratches, or damage to the mount tangs or mount face?

That's the thing. When compared to my other M lens it looks no different at all. It's incredibly strange.

Quote:

Is the aperture actuator properly aligned and fully operable with a flick of the finger with no roughness or hesitation? (A bent/misaligned actuator is a dangerous thing.)

Yeah it works incredibly smoothly. The lens seems to snag immediately on the body when putting it on, like it never lines up, but no matter how I look at it I can't seem to tell where the problem is.

11-27-2017, 04:00 PM	#1
ZombieArmy Pentaxian Join Date: Jun 2014 Location: Florida Posts: 3,210	Tight fitting Pentax-M 50mm f 1.7? Hi. I just got a Pentax M 50mm 1.7 on ebay. The lens is in immaculate condition but it seems to take a lot of force to get it on my k-01. To the point where I think it scuffed the mount a little bit. This doesn't happen with my 200mm which is also an M lens, what could be the cause?

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11-27-2017, 04:04 PM	#2
photoptimist Pentaxian Join Date: Jul 2016 Photos: Albums Posts: 5,121	Maybe a warped mount ring or bent bayonet tabs? I'd sight along the ring and tabs carefully to see if you can find the offending bend. A wee bit'o filing (with ALL lens opening covered in masking tape) might reduce the tightness if you can identify the source.

11-27-2017, 04:09 PM	#3
twilhelm Loyal Site Supporter Join Date: Feb 2009 Location: Florida Photos: Gallery \| Albums Posts: 2,369	Sounds like it was dropped on the mount. Do a close inspection side be side comparison with your 200. You’ll find the problem spot.

11-27-2017, 04:09 PM	#4
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,525	The location of the scuff marks should provide a clue where a possible problem could be. It may just be the luck of the draw - the mount on the lens as at towards the extreme in one direction of the specified tolerance and the mount in the other direction. Both are still within specifications but combined things work out to being stiff or tight.

11-27-2017, 04:35 PM	#5
ZombieArmy Pentaxian Join Date: Jun 2014 Location: Florida Posts: 3,210 Original Poster	I can not perceive any warping on the mount. The pentax 200mm will go on and turn with no effort, while when i put the 50mm on it will not move at all with the same amount of force.

11-27-2017, 04:44 PM	#6
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 8,188	The M50 mm are cheap enough on ebay. Get another and sell yours for parts

11-27-2017, 04:50 PM	#7
ZombieArmy Pentaxian Join Date: Jun 2014 Location: Florida Posts: 3,210 Original Poster	Originally posted by pschlute The M50 mm are cheap enough on ebay. Get another and sell yours for parts Sorry but we're not all in a situation where we can throw away money.

11-27-2017, 04:53 PM - 1 Like	#8
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 8,188	Originally posted by ZombieArmy Sorry but we're not all in a situation where we can throw away money Well then throw away the lens. Or would you prefer to keep damaging the camera mount?

11-27-2017, 04:54 PM	#9
ZombieArmy Pentaxian Join Date: Jun 2014 Location: Florida Posts: 3,210 Original Poster	Originally posted by pschlute Well then throw away the lens. Or would you prefer to keep damaging the camera mount? You could leave my thread.

11-27-2017, 04:57 PM	#10
photoptimist Pentaxian Join Date: Jul 2016 Photos: Albums Posts: 5,121	Originally posted by ZombieArmy You could leave my thread. Honestly, I think he's giving you good advice. The camera is worth more than the lens.

11-27-2017, 04:59 PM	#11
ZombieArmy Pentaxian Join Date: Jun 2014 Location: Florida Posts: 3,210 Original Poster	Originally posted by photoptimist Honestly, I think he's giving you good advice. The camera is worth more than the lens. I thought it was common sense to stop using a lens that requires 6x the force to mount onto the camera. The thread is for causes and possible solutions, not to tell me to call it all a loss "because it doesn't cost much".

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11-27-2017, 05:24 PM	#12
twilhelm Loyal Site Supporter Join Date: Feb 2009 Location: Florida Photos: Gallery \| Albums Posts: 2,369	Unfortunately that is part of the risk of ebay and buying old equipment. People will put things on for sale which look good but have a defect. I've lost a few and I've won a few. I bought a Sigma 28 which looked new, but was so badly de-centered it was not usable. Then I had a guy ask if I wanted a horrible looking lens in K mount with a bent filter ring and he threw it in for free. I got one of my favorite lenses, a K 55 1.8 which looks terrible, but has perfect glass.

11-27-2017, 05:26 PM	#13
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Originally posted by ZombieArmy I thought it was common sense to stop using a lens that requires 6x the force to mount onto the camera. The thread is for causes and possible solutions, not to tell me to call it all a loss "because it doesn't cost much". You already got the most probable cause, the mount is bent. Carefully examine where it is rubbing and you should find the issue. I sorta agree with the other poster about tossing it out, an M 50 f/1.7 should be what $25-$30? Not worth damaging your camera. But in your case you bought it on ebay so tell the seller it is defective and you want a return. If you don't like those options then get out a file as @photoptimist says. Or just keep using it and scratch up your camera mount. Leaving this thread now.............

11-27-2017, 05:29 PM	#14
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	It should mount easy and smooth unless the lens mount was poorly machined or has been damaged. As noted above, are there any signs of unusual wear, scratches, or damage to the mount tangs or mount face? Is the aperture actuator properly aligned and fully operable with a flick of the finger with no roughness or hesitation? (A bent/misaligned actuator is a dangerous thing.) You are right to be exercising full caution with the lens on your camera. A defective Russian fisheye permanently damaged the aperture actuator of one of my film bodies. You may want to be talking to the seller. Steve

11-27-2017, 05:34 PM	#15
ZombieArmy Pentaxian Join Date: Jun 2014 Location: Florida Posts: 3,210 Original Poster	Originally posted by stevebrot It should mount easy and smooth unless the lens mount was poorly machined or has been damaged. As noted above, are there any signs of unusual wear, scratches, or damage to the mount tangs or mount face? That's the thing. When compared to my other M lens it looks no different at all. It's incredibly strange. Quote: Is the aperture actuator properly aligned and fully operable with a flick of the finger with no roughness or hesitation? (A bent/misaligned actuator is a dangerous thing.) Yeah it works incredibly smoothly. The lens seems to snag immediately on the body when putting it on, like it never lines up, but no matter how I look at it I can't seem to tell where the problem is.