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[OM] Re: How hard and risky is it to repair a one touch zoom?

Subject: [OM] Re: How hard and risky is it to repair a one touch zoom?
From: Moose <olymoose@xxxxxxxxx>
Date: Mon, 24 Jul 2006 13:08:59 -0700
Fabio Fiorellato wrote:
> Hi list,
>
> I've recently discovered that my Tamron SP 35-105mm f/2.8, apart from having
> a mild amount of zoom creep, is not keeping correct focus when zooming from
> one end to the other.
>   
That's a real shame, as that is a great lens.
> I mean, if I focus a subject when the lens is at 105mm and then zoom the
> lens backwards to 35mm, the same subject is not in focus anymore (at least
> judging by the split image in the viewfinder).
>
> Of course the same happens when focusing at 35mm and then zooming at 105:
> the lens is acting as a varifocal lens, although it wasn't supposed to.
>   
I'm lucky, mine only creeps if held pointing at the ground and shaken. 
On the other hand, I just tried it and found that it is difficult to 
check for focus change with focal length. The zoom action is stiff 
enough (although not as stiff as my Zuiko 35-105) that it's hard not to 
move the focus while zooming. However, with care, it's clear that it 
does hold focus with zooming.

I think the proviso that zooms only hold focus when going from short to 
long fl is just manufacturers dealing with the reality that most folks 
can't focus accurately enough at the wide end to still be right at the 
long end.
> Furthermore, the distance reading at 35mm are totally wrong: a subject that
> is focused near infinite (>20m) when at 105mm, turns out to be at 5m or the
> like when correctly focused at 35mm.
>   
Definitely something that needs service.
> Given that years ago I had lost a Zuiko 35-105 with slow diaphragm because
> of an idiot repairman incompetency, I'd like to know from those of you with
> much experience in the field (John H. for instance) if repairing a one touch
> zoom is really that hard.
>   
As an amateur who has done a fair amount of camera equipment repair for 
myself, I've taken apart a Tamron one-touch zooms with fungus, just to 
see what's in there. They are quite complex inside. I think I might be 
able to fix creep, but not the focus problem.
> I can live with the problem (my guess is that at 35mm setting I won't focus
> right up to the minimum focusing distance, while at infinite there is no
> problem at all except for the bad distance scale readings) but I'm still
> considering the chance to let the lens be CLA'ed, if that doesn't turn out
> to be such a hard job.
>
> Needless to say, I'll go for another repairman rather than the one that
> killed my Zuiko 35-105 (R.I.P.).
>   
That's a real shame, a great lens and sticky diaphragm problems are 
often easy to fix. If you need a replacement, I have a Tokina 
35-105/3.5-4.3 I'd sell.

It is so close to the Zuiko in size, operation and performance that it 
has long been rumored that the Zuiko was made by Tokina. I bought mine 
mostly to check out that rumor. For various reasons, including internal 
design details, I concluded that the Zuiko isn't a Tokina, although 
before looking inside, I can see why people thought so

The reason I suggest it is that it is so cheap, compared to the Zuiko 
and to the faster Tamron, so the taxes, duties and fees should be more 
tolerable. It's in EX+ condition, with perfect glass and includes the 
hard to find (and cleverer design than the Zuiko) matching hood. It's 
for sale for $65, plus actual shipping & insurance.
> Anyhow, do you think that the focus misalignment should be a direct
> consequence of the increased zoom creep? When I first bought the lens the
> latter problem didn't showed, and neither did the misfocusing issue.
>   
I doubt it.

Moose

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