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View Full Version : Who has an EF 50mm f/1.4 USM lens?


Doug Kerr
December 21st, 2010, 08:42 PM
My Canon EF 50mm f/1.4 USM lens has always had a substantial amount of "lost motion" in the operation of the manual focusing ring. It occurs with the AF/MF switch in either position.

Here's the scenario.

The camera is trained on an object well within the focusing range. The current focus setting of the lens is beyond the subject distance.

While watching the image in Live View, I turn the focusing ring in the "near" direction to being the object into focus, but I go a little too far.

So I reverse the direction in which I turn the ring, now to the "far" direction. But the ring moves quite a way (about 1.5 ribs on the rubber tire, or about 4.5) before I see either any movement of the distance indicator or any change in the focus state of the image.

Then, after this "lost motion" is taken up, I see the distance scale begin to move in the "far" direction, and the image begins to change accordingly.

There is some dispute as to whether this is an inherent side effect of the very peculiar full-time manual focus mechanism used only in this lens, or if my copy just has some defect.

Could those having this lens take a minute to see if they work that way? It does not even need to be on a camera to check this.

Thanks.

Best regards,

Doug

Asher Kelman
December 21st, 2010, 09:02 PM
My Canon EF 50mm f/1.4 USM lens has always had a substantial amount of "lost motion" in the operation of the manual focusing ring. It occurs with the AF/MF switch in either position.


Doug,

Luck would have it that the EF 50 1.4 was already on my 5DII. I used live view and MF to check for any gap in focus response as the focus ring direction is changed. Even using 10 X magnification, I couldn't detect any lack of responsiveness. The slightest movement in the new direction always altered the focus in the expected manner.

So, at least under the conditions I used, there appears to be no "lost motion" in the MF of the Canon EF 50 1.4.

Asher

Doug Kerr
December 21st, 2010, 09:54 PM
Hi, Asher,

Doug,

Luck would have it that the EF 50 1.4 was already on my 5DII. I used live view and MF to check for any gap in focus response as the focus ring direction is changed. Even using 10 X magnification, I couldn't detect any lack of responsiveness. The slightest movement in the new direction always altered the focus in the expected manner.
Thank you so much for that prompt and unequivocal report.

In addition to the focus changing immediately upon motion of the manual ring in either direction, I assume there was also not any lost motion with respect to the visible movement of the distance scale.

And, to be absolutely sure there is no chance of misunderstanding, if you "rock" the manual ring back and forth a very small amount, I assume the distance scale follows.

So, at least under the conditions I used, there appears to be no "lost motion" in the MF of the Canon EF 50 1.4.

That's good news. Among other things, that means that Canon should be able to fix mine (once they pay attention to my complaint - it has gone back for a second pass).

Thanks again so much.

Best regards,

Doug

Ben Rubinstein
December 22nd, 2010, 03:10 AM
Although the focus ring on mine is somewhat sluggish, it doesn't seem to display the characteristics you describe. Keep in mind that this lens does not have full time MF due to the older 'micro USM' motor, you need to put it into MF otherwise you may strip the gears.

Doug Kerr
December 22nd, 2010, 06:32 AM
Hi, Ben,

Although the focus ring on mine is somewhat sluggish, it doesn't seem to display the characteristics you describe.
Thanks for the report.

Keep in mind that this lens does not have full time MF due to the older 'micro USM' motor, you need to put it into MF otherwise you may strip the gears.
Not so. Although most EF lenses with a micro USM motor do not have full-time MF, the 50 mm f/1.4 USM does. To that end it has a mechanism unlike any other EF lenses.

I do not yet know the exact nature of the mechanism, but I believe that it is in fact a differential, conceptually (but not physically) like the one in the ring USM lenses with mechanical FTMF. (All ring USM motors have FTMF, but in a few it is "fly by wire".)

It is in fact the uncertainty over the nature of the mechanism in the 50/1.4 that made me uncertain that the "lost motion" I experienced was actually a misbehavior in my copy (as contracted to an unfortunate but unavoidable side effect of the working of the mechanism).

Thanks again so much for your report.

Best regards,

Doug

Doug Kerr
December 22nd, 2010, 06:51 AM
Curiously, four guys on dpr report exactly what I describe, most mentioning that they hate it. One guy said "oh yes but he had gotten used to it" and didn't even realize anymore that there was such a thing until I asked about it.

So there is still some mystery here.

One question might be about the vintage of the lens copies. Mine is about 4-5 years old (s/n 89302535).

Asher, Ben: is there any chance that your copies might be newer than that?

Best regards,

Doug

Bart_van_der_Wolf
December 22nd, 2010, 09:52 AM
So I reverse the direction in which I turn the ring, now to the "far" direction. But the ring moves quite a way (about 1.5 ribs on the rubber tire, or about 4.5) before I see either any movement of the distance indicator or any change in the focus state of the image.
[...]
Could those having this lens take a minute to see if they work that way? It does not even need to be on a camera to check this.

Hi Doug,

I just checked, my copy has something like 0.5-1.0 'rib' play when manually changing focusing direction, before it actually does show a change on the distance scale. I'd have to double check with 10x Live View, but I don't think it will show anything different.

Cheers,
Bart

Doug Kerr
December 22nd, 2010, 10:15 AM
Hi, Bart,

I just checked, my copy has something like 0.5-1.0 'rib' play when manually changing focusing direction. I'd have to double check with 10x Live View, but I don't think it will show anything different.

Thanks so much.

A check just observing when the distance starts to move scale is quite adequate (not even looking at what happens to focus).

It begins to look as if all the lenses have some play, but it might well be that certain versions of the mechanism (it is already at issue 009 of the second part number) have reduced its degree, which is certainly worthwhile.

Maybe Chuck just got an especially good one (but in fact his report that it shows play when reversing direction at the end of travel makes me suspicious).

My copy is about 4-5 years old.

I am fascinated by several aspects of this matter, and will probably end up buying a drive mechanism just to disassemble (it will cost me about USD75.00 delivered).

I am also trying to link up with a guy in Singapore who has completely dissembled the lens in order to get the elements out to remove fungus.

Thanks again.

Best regards,

Doug

Bob Latham
December 22nd, 2010, 11:21 AM
I believe that the 50/1.4 has an inherent problem with the lug which locates into the focus helicoil. If the lens is stored at the extreme of the focus range then the lug is prone to wear and will eventually shear off when it gets thin enough. I suspect that the backlash you experience is the result of the lug's diameter being worn down somewhat.

Bob

Ben Rubinstein
December 22nd, 2010, 01:43 PM
Mine is 4 years old approx. I almost never MF with it and I doubt that the focus is ever stored at the extreme, I also never shoot with it at infinity so I doubt it goes into the bag like that. Apologies over the mistake over FTMF, I had understood this lens to behave as I mentioned.

Canon need to pull their finger out and make a newer version of this lens with modern USM and better build. It's a nice lens if you have a good one, dreamyish at f1.4 though with weird bokeh, sharp and nice at f1.8 and super sharp from f2.8 onwards. The sigma f1.4 lens however is much much better with incredible bokeh, razor sharp wide open, etc. Problem is the inconsistent focus on canon bodies which plagues this lens and which has held me off thinking of buying one especially for my 5D classics with no MA ability.

Doug Kerr
December 22nd, 2010, 02:07 PM
Hi, Bob,

I believe that the 50/1.4 has an inherent problem with the lug which locates into the focus helicoil. If the lens is stored at the extreme of the focus range then the lug is prone to wear and will eventually shear off when it gets thin enough.
I suspect you may be talking about this problem area (a disgraceful design):

http://dougkerr.net/images/technical/_MG_8902-Edit.jpg
EF 50mm f/1.4 USM (not mine) - focusing cam barrel (infinity position) and cam follower

I suspect that the backlash you experience is the result of the lug's diameter being worn down somewhat

Well, it's hard to imagine that causing backlash in just the way I experience it. Note that when I move the manual focus ring, it is not just that the inner barrel (with the
lens elements) doesn't start to move right away. The focusing cam barrel itself (with the helical tracks) doesn't start to move right away (the distance scale is fastened directly to it, so we can see if it moves).

The lens has hardly ever been used, and I think not ever dropped when extended.

But indeed there must have been something awry in that area, since the cam barrel was just replaced at the Canon FSC. (The note in the service ticket explaining what they did was badly scrambled, so I can't be sure!) But the play is still just as it always was.

Thanks for your input.

Best regards,

Doug

Bob Latham
December 24th, 2010, 01:55 AM
I see you point now Doug. The 50/1.4 does seem to be one of the more injury prone of the mid-range offerings from Canon.

Bob