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09-17-2009, 05:12 PM   #1
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Help diagnosing lens problem - newbie :o(

If anyone can help me here I would greatly appreciate it. I bought a Tamaron AF70-300mm F/4-5.6 Di lens and it is only 3 months old and I picked up my camera one day to shoot some pictures and the lens wouldn't work. It's been babied since I got it, I always wrap it back up in bubble wrap when I take it off and to my knowledge have done nothing wrong. I don't know much about lenses or the mechanics of them and it is my first so I'm flabber gasted over this. When I looked through the viewfinder, everything looked very dark no matter what I did. I did find a post on your forum from someone who had the very same problem (Jester????) and would like to know if he found out his problem. The lens won't focus on anything either. It's still under warranty but I'm leary about sending it because they could look at it and then come back to me with a bunch of technical jargon and say it was mis-used or something and I would never know the difference. Can anyone ease my mind on this matter. I'm even scared to send it in the mail thinking I'll never see it again ....hmmm....maybe I baby it too much )

09-17-2009, 08:06 PM   #2
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There are a couple current models of that lens. Lets assume you do not have the "Di" model. Looking at the pics it seems there is an aperture ring at the base where it connects to the camera. The ring has numbers ranging from 4-22 with an "A" at the end. If the ring turns, you need to click it back into the "A" position most likely unless you were setting the aperture manually for each shot...not likely. A little button should be near the "A" and need to press it to get it clicked into the "A" position. The ring should unable to turn once properly in the "A" position.

That makes sure the camera can control the aperture on the lens. If it was set at 22 by mistake it could have looked dark but still should have focused. Anyway, one thing at a time. I dont have your lens or even know what camera you have or what you know so try that and get back to us.

ps, if you DO have the "Di" model, forget all the above and we need to know more. Camera? Settings (Green mode if Pentax?) etc.

edit - you have a MACRO/NORMAL switch. You are familiar with that function by now maybe but make sure its in NORMAL mode. If there is another switch for Manual/Auto focus, put it on Auto.
09-17-2009, 08:37 PM   #3
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Welcome Digimom.
Indeed the only thing I can think of is the aperture ring that is set at something like 22 rather than A (if it's the model with the ring right at the bottom of the lens - the end that attaches to the camera).

If not, we'd have to go back to the drawing board and get more info from you.
Is the autofocus mode set properly on the camera body (and on the lens)?
Tell us some more.
09-17-2009, 09:28 PM   #4
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Sorry if you find this offensive but.. did you screw the lens in until it "clicks?

09-17-2009, 11:10 PM   #5
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Hmmm... well, first, welcome to the forum! Ok, now... hmmmmm. It seems you do have the Di version, which looks in the photos I can find of it to not have an aperture ring - if that's the case the it can't be the "aperture ring set to 22" problem some have theorized... My next guess would be Andi Lo's - that the lens isn't fully engaged on the mount. This would potentially fail to push the aperture lever enough to open the aperture, and the lens would be very dark - also the AF mechanism would not be able to engage if the lens were not rotated enough on the mount.

It's also possible (though unlikely based on how you treat this lens) that the aperture mechanism has failed internally, and the lens is remaining stopped down to min aperture all the time (which would prevent AF from working simply because it would be too dark).

I wouldn't worry about sending a lens in to Tamron for service - I've done it... it took a couple months, but the lens came back fixed under warranty.
09-18-2009, 12:07 AM   #6
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Welcome to Pentax Forums, Digimom,

Even if you did have an aperture ring on your lens, and it set to 22 I believe that your camera is design hold it wide open.
So that isn't your problem
It not being on all the way is one possibility, however I would imagine that was the first thing you tried.

So I'm going to say, it sounds like sticking aperture blades. Which you can't fix yourself
So, if the lens is on warranty you might want to look into getting it repaired. I don't know how good or bad Tamron are with their warranty repair. I hope that it doesn't take too long for them.

If it isn't under warranty there is some fellow in the US, whom several board members recommend. Although I don't remember his name, someone may bring it up.
Here in Canada I know that Gentec International repairs Sigma lenses, however I don't know if they'll touch anything else. They did a great job repairing one of my Sigma lenses
09-18-2009, 12:10 AM   #7

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Sorry to ask the obvious: does this symptom (dark viewfinder) happen with other lenses, or just the lens in question?

QuoteOriginally posted by little laker Quote
If it isn't under warranty there is some fellow in the US, whom several board members recommend. Although I don't remember his name, someone may bring it up.
If you mean Eric Hendrickson (, I don't think he does AF lenses.
09-18-2009, 12:34 AM   #8
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QuoteOriginally posted by SOldBear Quote

If you mean Eric Hendrickson (, I don't think he does AF lenses.
I believe that's whom I was thinking of. Thanks for that, I didn't know he was a manual guy only. It makes sense though.

09-18-2009, 03:00 AM   #9
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Thanks everyone

Wow...I wasn't expecting so many replys ) Thanks to all. The lens I speak of is the Di model and it does have an aperture ring and I did try it in the A positions as well as every other position. My other lens (the one the camera came with) which is a Pentax Km works fine so I do know it is a problem with the lens.
When I mount the lens, I do turn it until it clicks so I know that isn't the problem. Based on other threads I've read in this forum as well as a few of the comments in this thread...I think the problem may be the aperture blades are stuck. I've tried the lens set to Macro and Normal and that didn't do anything either. Is it normal for a lens to just stop working like this? I use to have a Minolta Di7 and used it for years and just bought the Pentax this spring with the extra Tamron lens so its my first experience with a camera that I can change lenses. As I mentioned, I do baby it so it's unlikely due to abuse. Thanks again for all your help everyone.
09-18-2009, 11:49 AM   #10
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Welcome to the forum!

I don't think the problem was a post by me (at least I don't recall having that problem or posting about one like that...maybe there's another Jester? Then again, my memory's not all that great)

Your last post shot down my two best ideas....not taking off the lens cover (don't laugh, it happens), or a dead or dying battery in the camera.
09-18-2009, 12:55 PM   #11
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