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07-03-2012, 05:06 AM   #1
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Promaster 28-210 with a weird problem.

I have this Promaster (made by Cosina) 28-210.

It used to belong to my wife until a few days ago. She liked my 28-300 Tamron, and she had complained of the AF being flaky on the Promaster, so I swapped her. After shooting a few photos with it, I noticed a weird quirk... It will only focus to infinity from about 200 to 210mm. From 28 to 200 it doesn't quite get to infinity. It's like the focus stop needs to be just a tiny bit farther.

Any way to fix this? I know it's a cheap lens, but it's a surprisingly decent performer. I bought it a couple of years ago brand new & wasn't aware if the issue 'til recently. Unfortunately, I don't think the eBay seller was an authorized dealer, so no warranty.

Thanks,
Bobbo :-)

07-03-2012, 05:26 AM   #2
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Hi

There is always an adjustment that can be done, not having seen any of those lenses I can't tell you exactly how but usually
there is a way to adjust the front element.
On Tamrons there are 3 screws under the piece that holds the Hood that allow you to turn the element to move it in and out.
Most likely there is something similar.
07-03-2012, 05:48 AM   #3
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Hmmmmm... I don't see any screws on this thing, except for on the mount.
07-04-2012, 06:22 AM   #4
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Sometimes it is a little tricky to find...

I can't find a decent picture of the front of one on the Net, check if that plastic ring around the front element comes off. Could only be held
by sticky tape and not screwed on or that big ring around the front slides back. Anyways there is a way to move that front element as it is the
last adjustment made and some other human did it before you.

07-04-2012, 06:44 AM   #5
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With zoom lenses it is necessary for the register (distance from sensor to mount flange to be as near exactly correct as possible, and the rear group position,rearmost, at widest FL must be correct.
Otherwise the lens will not focus sharply thru its range.

Maybe the mount flange has moved relative to lens barrel or has been replaced with shims missing etc ?

On a non zoom. the register dimension is not critical for sharpness, only for infinity focus.
07-05-2012, 07:28 AM   #6
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I e-mailed Promaster and asked about warranty service. It has a lifetime warranty. I bought it new, but unfortunately I can't find the receipt. I fully expect them to be as helpful to me as an air conditioner would be to an Eskimo.
11-09-2013, 07:57 PM   #7
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Slide off the rubber grip. Under that there is a metal door held on by tape. I haven't opened it yet, because I'm in the field, but there should be adjustments under that door.

Charles.
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