Autofocus slowed

ericB&W

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My Tamron 70-300 af. DI-VC started to focus very slowly, i've tried with Canon eos 33, Canon eos 5, 630 and 650 film cameras and Canon 550
digital, all focused slow, so can't be a camera fault .
The strange thing is , that i tried to spray inside with a compressed air can and it returned to focus normally, that is, fast
but after a while it turns again to focus slowly and sometimes doesn't reach the focus point , so i have to manual override.
The stabilizer works flawlessy .
It is the fourth time that i repeat the experiment, spray the air , works again and then , after some minute is slow again.
i thought that could had accumulated some dust in some critical point indide , for this reason i tried with the air,
but now i can't understand why this issue reappears again and again .
 

Sirius Glass

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Now that you have done about all that you can do other than give it several hard wacks with a hammer, so send it in for a CLA and be done with the problem.
 
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ericB&W

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Sirius Glass said:
Now that you have done about all that you can do other than give it several hard wacks with a hammer, so send it in for a CLA and be done with the problem.
Click to expand...

What i can't understand is why the air compressed solve the problem for about an hour
and then the problem comes out again .
If something was broken , air should have no effect .
Strange things happens with modern cameras and lenses, months ago the stabilizer of the same lens stopped to work on Canon eos 33 but only in A-T-and Manual modes while with the others auto programs, landscape, portrait, close-up etc. worked perfect, this issue after a couple of months disappeared and now the stabilizer works again perfect .
 

Sirius Glass

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May be the camera is complaining that it does not get out enough and needs fresh air.
 
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ericB&W

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As i suspected , is something connected with temperature .
The air compressed cools down the inner parts,so made a test and put
a couple of minutes the lens in the freezer without using air compressed and then the autofocus
was perfecly fast .
 

Sirius Glass

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ericB&W said:
As i suspected , is something connected with temperature .
The air compressed cools down the inner parts,so made a test and put
a couple of minutes the lens in the freezer without using air compressed and then the autofocus
was perfecly fast .
Click to expand...

Until it warmed up?
 

MattKing

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Most likely something to do with lubricant that is either not where it should be or not as "liquid" as it should be.
 

Sirius Glass

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MattKing said:
Most likely something to do with lubricant that is either not where it should be or not as "liquid" as it should be.
Click to expand...

Post #2 has an easy to implement fix to the problem.
 

koraks

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ericB&W said:
yes , when warms again starts to not work properly .
Click to expand...

Sounds like excessive friction due to fouling/dirt. At low temperatures, components will shrink a little. Maybe at this stage of the progression of the problem, this effect is sufficient to make thing seem and function normally. As it warms up and parts expand, friction becomes excessive.

Either get it CLA'd as @Sirius Glass says, or open it up and start cleaning.

MattKing said:
Most likely something to do with lubricant that is either not where it should be or not as "liquid" as it should be.
Click to expand...
I'd expect a positive correlation between temperature and correct functioning in that scenario, not a negative one. Most lubricants tend to be more viscous when cold.
 
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ericB&W

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MattKing said:
Most likely something to do with lubricant that is either not where it should be or not as "liquid" as it should be.
Click to expand...

But here is the contrary, a lubricant as anything , becomes more liqiuid with hot temperature while , in my case, if i put the lens in the freezer then works , while at ambient temperature a.f. doesnt works.
Anyway for all these reasons i still prefer old mechanical stuff .

A nikon F80 died two years ago for power problems, i bougth another one and now this strange thing happens :
I switch on , thake the first shoot and is ok, then the display disappear and the camera doesn't work, after about a minute turns ok ready to shot again, if i want to shoot immediately another photo, i have to
switch off, then immediatel switch on , it takes less than a second to do this operation and in this way
the camera works properly .
 

MattKing

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If the lubricant is grease, you don't want it liquid - it doesn't stay where you want it .
 
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