Bayonet mount play

My 5D2 appears to have some play with certain lenses, mainly the EF 70-200 F4L IS and the EF 400 F5.6L USM: if I twist the lens whilst keeping the camera steady or viceversa, the lens/camera turns a wee bit: probably less than a millimetre or two, but still: it feels secure but loose. This camera has always been this way; some lenses are a 'perfect' fit with no moving, and some others feel loose. The 400mm I'm finding particularly annoying as, being the heavy lens it is, I'm experiencing that looseness constantly.

Is there anything that can be done about this? Or should I even worry about it?

It's making me nervous (and subsequently peeing me off :mad.

TIA

It's normal.

Yeah, absolutely normal. There are tolerances at play here, partly to allow some slack to make sure they will drop in behind the locking mechanism OK, and also manufacturing variances. So long as the lens goes past the locking pin and the mechanism can lock, some rotation is perfectly acceptable and has no affect on the image.

The lenses that don't move are at the tighter end of the tolerance range that is all. The slacker ones are at the other end, there is nothing wrong with them.

Alright, you've set my mind at ease, mates. Thanks a lot!

sandpiper wrote in post #16810485
Yeah, absolutely normal. There are tolerances at play here, partly to allow some slack to make sure they will drop in behind the locking mechanism OK, and also manufacturing variances. So long as the lens goes past the locking pin and the mechanism can lock, some rotation is perfectly acceptable and has no affect on the image.

The lenses that don't move are at the tighter end of the tolerance range that is all. The slacker ones are at the other end, there is nothing wrong with them.

There is nothing technically wrong with them. But it shows that canon does not spec their tolerances to be tight.

Frodge wrote in post #16810648
There is nothing technically wrong with them. But it shows that canon does not spec their tolerances to be tight.

They are tight enough to work perfectly, making the tolerances tighter would not improve the performance in any way, but would quite possibly increase production costs (and therefore selling price). There has to be SOME play there or any expansion on a hot day could make the lens awkward, or even impossible, to mount or dismount.

Canon specs tolerances as tight as they need to be to get the job done, without unnecessary expense, that is normal manufacturing practice.

I went through the same thing around the first of the year, following is what the good folks had to say to me then to put my mind at ease.... I believe all is well (but still wish it were tighter !)

https://photography-on-the.net …/showthread.php​?t=1353685

Cool. One of my concerns was (is?) that too much play might wear the mounts over time. But maybe that won't happen.

Alveric wrote in post #16811697
Cool. One of my concerns was (is?) that too much play might wear the mounts over time. But maybe that won't happen.

Well, there is quite a bit of play on my old 5D with two of my most used lenses. I've had it 9 years now and put over 100k clicks on it and there is no wear on the mount so far.

Alveric wrote in post #16811697
Cool. One of my concerns was (is?) that too much play might wear the mounts over time. But maybe that won't happen.

If you finally do wear something out, it can be replaced. But a more interesting question: How many threads here have you seen where people have needed to replace the mount on the lens or camera because of wear? That should give you an indication how likely you are to need to be worried.

sandpiper wrote in post #16810684
They are tight enough to work perfectly, making the tolerances tighter would not improve the performance in any way, but would quite possibly increase production costs (and therefore selling price). There has to be SOME play there or any expansion on a hot day could make the lens awkward, or even impossible, to mount or dismount.

Canon specs tolerances as tight as they need to be to get the job done, without unnecessary expense, that is normal manufacturing practice.

Working properly and having perceivable slop are two different things. Is Raheem have a lens that worked properly and had the tighter spec. You? Slop is never good, in fact, it eventually creates more play and slop in the fitting.

Frodge wrote in post #16812266
Slop is never good, in fact, it eventually creates more play and slop in the fitting.

Wrong. So very much wrong. Much mechanical products are intentionally given some slop because it needs to be there - it's the slop that make things function correctly.

While lots of people instantly seize up about wikipedia references, that still doesn't make the information bad.
http://en.wikipedia.or​g/wiki/Engineering_fit

Note:
RC1 to RC5 are a series of fits, where RC1 has the least play.

Transition fit RC1: Close Sliding Fits:
"This kind of fits are intended for the accurate location of parts which must assemble without noticeable play."

Above is the kind Frodge wants.

RC2: Sliding Fits
"This kind of fits are intended for the accurate location but with greater maximum clearance than class RC1. Parts made to this fit turn and move easily. This type is not designed for free run. Sliding fits in larger sizes may seize with small temperature changes."

RC2 has more play than RC1, but may still seize with small temperature changes. I bet most owners of camera gear do not want their lenses to seize up even at small temperature Changes? So both classification RC1 (where you can't feel any play) and RC2 represents a too tight fit for our lenses.

RC3: Precision Running Fits
"This kind of fits are about the closest fits which can be expected to run freely. Precision running fits are intended for precision work at low speed, low bearing pressures, and light journal pressures. RC3 is not suitable where noticeable temperature differences occur."

Even when stepping one step further, RC3 can still have issues at larger temperature changes.

But anyway - what is important with the lens mount is:
1) The lens must never fall off.
2) The lens must be kept at a very well defined distance from the sensor, so there is a need for some kind of bayonet fitting to press the lens towards the camera body.
3) There must not be any light leak between lens and body.
4) The mount must be durable, since people needs to change lenses quite often.
5) It must be strong, so it can be used with very heavy lenses without failure.
6) It must be possible to manufacture at a reasonable cost.

I'd say that Canon's mount fulfills the requirements.

The only issue that could be debated, is the position of the release button. But that's a separate debate.

pwm2 wrote in post #16812315
Wrong. So very much wrong. Much mechanical products are intentionally given some slop because it needs to be there - it's the slop that make things function correctly.

Some things need some play, for instance, a valve in a car. You set it cold with a feeler so that when it comes up to temperature, the slop disappears. Most mechanical thins have enough "slop" in order to be able to move. For example, a folding knife joint, a ball joint, a tie rid end. If there was zero "slop" it would be static and bind. When however the slop has a loose feeling, it is technically out of tolerance in its machining. Most lenses fit tightly once mounted. He ones that have perceptible looseness are at the loose end of what Canon calls "spec". If a lens and it's mount is supposed to have this perceivable slop or movement, then the ones that are tighter have to be out of spec. Pick your poison. A loosely specced interface and tightly specced interface cannot both be ideal.

You still haven't understood the issue.

There must be manufacturing tolerances.

And there must be slop.

And most specifically: that locking pin must never fail to engage because the tolerances are too tight so there is pressure on the side of it. If it doesn't engage, then you'll soon cry about broken glass when the lens is on the ground.

Right now, you are chasing shadows.

You think "some things need some play". Almost every mechanical fitting that is intended to come on/off needs play. Because we aren't supposted to need tools or heat when mounting/dismounting. And the locking pin is the one that stops rotation - but isn't allowed to see any side forces to make sure the spring can operate.

Most of the time when you play with some mechanical gear and think there isn't any slop, there really is. But there are some springy material there that hides the slop so you don't notice it.

Talk about "out of spec" the day you have links to the actual specifications, together with real measurements of your claimed "out of spec" lenses. But remember that both camera and lens must have +/- tolerances in that specification, whatever level of precision the specification claims. And these tolerances can't be arbitrarily selected because it must both be possible to manufacture and the final products must with all combinations of min/max tolerances must operate over the full temperature range.

Your valves? Well they operate at a quite limited temperature span. There isn't a heater that keeps a lens mount at an almost fixed temperature. And there is no layer grease that masks slop.