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01-28-2009, 12:50 PM   #1
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Slower Than Molasses!

So a few months ago I purchased a Tamron 35-90mm f4-5.6 AF lens (apparently they are rare to find and rarer still to get any info on!)...I needed to fill a focal length gap with minimal overlap and this seemed like a good lens for it. When I received it I automatically installed it on my K200D to see what it could do. No surprise that it was a bit searchy in low light as I have found with other Tamron lenses but the biggest surprise was how bloody slow it Auto-focuses...I'm talking frustrating slow. I had no time to be upset because I was leaving on vacation and I REALLY needed it.

It shoots phenomenal pictures...I took it to Ireland and used it as my primary lens with excellent results...it was completely USELESS for anything other than Still-life and landscape shots. Luckily I had my K10d with my Vivitar Series 1 19-35mm and a Sigma 75-300mm to capture flying birds and the running Toddler daughter.

What would make a lens like this so Slow? Is the mechanism bad? Could it be it's Connection with the Camera?

Any insight into this would be appreciated.

01-28-2009, 01:16 PM   #2
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Could be the lubricate in the focusing helical is getting stiff. Lubes can get very thick as the fluids evaporate from the grease.

I have a Tamron 28mm that takes both hands to turn. I plan on redoing it soon.
01-28-2009, 01:30 PM   #3
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Another note.
If it is due to stiff grease. It may put an abnormal load on the auto focus motor assembly.
Wouldn't want a burned out motor., or stripped gear.
01-28-2009, 07:04 PM   #4
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Thanks for the info...now I have never taken a lens apart and I fear I may damage it in some form. How would I go about checking the lubricant and what should I be looking for in it's viscosity if it is, indeed, gunking up?

Any other ideas from other people would be appreciated...I forgot to mention that I bought it from a guy who had it sitting on a shelf for a LONG time...probably 15 years...

01-28-2009, 07:21 PM   #5
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With the lens off the camera, just turn the focus ring. An AF lens should have very low or no resistance to turning, and the same effort through its range. You can also turn the AF drive screw with a common screwdriver to see if that mechanism is dragging.

If it was me, I would not bother taking it apart unless you're really adventurous. AF zooms are complicated, and the focus mechanism is probably hidden under everything. You can easily find a lens with similar specs on eBay for $30-50, possibly with a free film camera attached.
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