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Modifying a Canon 50mm 1.4 LTM
Old 02-13-2019   #1
Mjd-djm
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Modifying a Canon 50mm 1.4 LTM

I picked up one of these lenses cheap. The focus is very stiff so I took it apart to re-lube. It was fairly straight forward and everything seemed to work better after lubrication... until I slotted the helicoid back into the mount - stuff again. Iím pretty sure either the focus lock notch is rubbing against the helicoid as it turns, so I might try machining it to take a bit off.

While I was at it I was thinking I might as well try to machine the helicoid to get it to focus closer. Has anyone tried this on this lens?
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Old 02-16-2019   #2
Dez
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Presumably the helicoid was smooth at one time, so if it's tight now it's likely to be dirt, damaged threads, or warpage. I imagine you cleaned it thoroughly before re-assembling.
I usually use light white grease on a helicoid, and very little of it.
It's a good idea to check with a caliper to see if it's out of round. If it is, be extremely careful trying to rectify that; it's so easy to make things much worse.
I f you have suspicions about the threads, I would go over the inside and outside threads carefully with very fine steel wool.


Increasing the focus range is a lot of work and may not be worth it. It has been a long time since I had one of these apart, so I don't recall if this is a peg-in-slot affair or a stop block. You won't run out of thread, but will probably not be able to extend the range by much. If the body you plan to use it on doesn't focus closer than 1M, I wouldn't bother at all.

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Old 02-16-2019   #3
retinax
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Before you try more radical things, try with less grease. Too much, and that is less than one might think, will make the focus rather stiff.
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Old 02-16-2019   #4
Mjd-djm
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Iím really confused by it to be honest. After greasing it feels awful... like itís dry as a bone... a really scratchey, un-smooth feel. Maybe Iím just using the wrong grease... lithium based in a spray can. Although Iíve heard this should work fine.
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Old 02-16-2019   #5
retinax
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Quote:
Originally Posted by Mjd-djm View Post
I’m really confused by it to be honest. After greasing it feels awful... like it’s dry as a bone... a really scratchey, un-smooth feel. Maybe I’m just using the wrong grease... lithium based in a spray can. Although I’ve heard this should work fine.
OK, if it feels scratchy, the main problem is probably not too much grease...
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Old 02-17-2019   #6
Musashi1205
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Quote:
Originally Posted by Mjd-djm View Post
Iím really confused by it to be honest. After greasing it feels awful... like itís dry as a bone... a really scratchey, un-smooth feel. Maybe Iím just using the wrong grease... lithium based in a spray can. Although Iíve heard this should work fine.
I recently did this too. You should first clean the helicoid with cleaning petrol, Q-Tips and a old toothbrush. I also used lithium grease, but not as a spray. This would probably be too fluent.
I applied a little bit of the thick grease with a Q-Tip on both parts.
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Old 02-19-2019   #7
TenEleven
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Quote:
Originally Posted by Mjd-djm View Post
I’m really confused by it to be honest. After greasing it feels awful... like it’s dry as a bone... a really scratchey, un-smooth feel. Maybe I’m just using the wrong grease... lithium based in a spray can. Although I’ve heard this should work fine.
The grease is perhaps not viscous enough.

Also as others have said you need to make sure that the helicoid is completely and utterly clean before re-greasing and re-assembly. I use a bath of isopropyl alcohol and an old toothbrush. Then a second once-over with a q-tip and some lighter fluid. Just to be on the safe side.

Spots of old grease often have rough particulate matter in them which will make the helicoid feel scratchy and uneven. So it looks like you'll have to take it apart again and make sure it's fully clean, a superficial clean won't do. It needs to be spotless.
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Old 02-19-2019   #8
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If you have an ACE Hardware nearby this stuff works great:

https://www.acehardware.com/departme...reases/8138307

Shawn
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Old 02-19-2019   #9
peterm1
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Quote:
Originally Posted by Mjd-djm View Post
Iím really confused by it to be honest. After greasing it feels awful... like itís dry as a bone... a really scratchey, un-smooth feel. Maybe Iím just using the wrong grease... lithium based in a spray can. Although Iíve heard this should work fine.
I have used the spray based lithium grease as well and it worked perfectly fine with my lens.

But of course one should not spray it onto the helicals. After thoroughly cleaning the old grease off the helicals, I sprayed my new grease into a clean receptacle and then, using a Q tip, carefully and sparingly wiped some onto the newly cleaned lens helicals. A few dabs here and there worked, followed by re-engaging the helicals and twisting them to spread the grease evenly. I found a little too little is better than a little too much in the long run. At first I though that spray based grease would be too thin (but it was all I could find.) Turns out it was perfectly OK.

It could be possible you have applied too little or have not yet allowed it to spread out evenly by manipulating your helical.
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Old 02-19-2019   #10
Beemermark
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You can buy some 39 screw in close up filters cheap for close up macro work. I have some that I'll sell you. Same issue as modifying yours. Focusing stops at 1 meter.
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