Lens recalibration

[peter_bury1]

I was just wondering ...

 

... has anyone ever had a lens go obviously out of alignment and

need recalibration?

 

The only reason I ask is that I, like some other people here, had

the dreaded 10d focus issue with some of my lenses. The (VERY

helpful) guy at the store suggested the body + lens recalibration

route and mentioned that over time lenses can "drift". I can't say

I've ever heard of this outside of the digital world - but, hey, I

was just curious.

 

Cheers

[roland_vandenbulcke]

Hi, I have only my 10D from now and only 2 lensen, a old EF 3.5 4.5 35-105 and a new tamron 28-300 ( where i cant believe the results from) and no back or front focus in real live situations. I readed a lot about the problem and was realy afraid at the start but after a little time a knew that the problem was me .... Time to slow and so on. Take a tripot and shoot and look closely to your pictures and dont believe to mutch what some people say ( as I did in the beginning) look at my last uploads full opening at 300 ( not once )

hope for you that your problems be solved.

[peter_bury1]

Roland, thanks for the answer.

 

I think I should rephrase my question, though. My DIGITAL focus issue is resolved (one way or another).

 

I'm just curious if anyone has ever had this problem OUTSIDE the digital domain - ie, a lens noticably loosing it's focussing ability and needing a tweak from the Canon (or anyone's) engineers.

 

Pete

[ron c sunshine coast,qld,a]

Many older lenses need infinity focus recalibrating but that's not really an optical/mechanical problem but a pure mechanical one-a simple adjustment fixes it.Newer lenses though rarely have this problem because they are made to go past infinity anyway-they depend on the autofocus to stop them at the right point.

<P>As for the optics themselves-most cheap modern lenses have glass lens groups molded in plastic so the whole group is just one peice.The different groups can get loose in their focus/zoom cam tracks though,so some lenses have different size rollers made for them for when they wear.The 28-105/3.5-4.5 is one example.Most cheaper zooms have no such adjustments available.

<BR>Better built lenses are a whole different story(from what i've seen).Alot of the elements are still held by machined metal parts and are usually completely disassemlable.I assume there are similar shims/rollers available to keep the moving groups aligned.I'm not sure what happens with the individual lens elements though.Some people say to never take apart a lens because it will not go together exactly the same but with the older manual focus lenses i've worked on i have not seen any evidence that the elemets CAN go in wrong-there is no way to put them in crooked.Testing lenses after i've worked on them seems to prove this...

<BR>I presume modern lenses are built along similar lines?

[andrew robertson]

I don't know about Tamron, Sigma, or Nikon, but Canon's lenses are all glass. The only

plastic used (resin actually) is in replica spherical elements and DO elements.

[ron c sunshine coast,qld,a]

I allways write things too briefly.What i meant by 'molded in plastic' was that the glass elements are held together by a plastic molded part which basically makes them mostly immune to being bumped out of alignment

[peter_bury1]

Thanks for all the replies. I guess with the mechanics of most lenses, something pretty major would have to happen for a focus problem - slipped elements and the like.

 

So in the occasional recalibrations done by Canon on EF lenses with the 10D, does anyone know what happens? I'm assuming it's purely electrical (motor tweaking or something).

 

Again - to emphasise - I don't have 10D focus problems and this is NOT a "my £1200 camera's a waste of space" type of question.

 

Just wondering about things.

 

Cheers,

 

Pete