[Jester2138]

Hello everybody

I have a Pentax K100D and the kit 18-55mm lens. I have been very happy with the camera/lens, so I decided to expand on it and buy a longer lens. Not wanting to spend too much, I bought a Tamron 70-300mm lens. It seemed to be working great, and just when I thought the Gods were smiling upon me, something went wrong. Or at least I think something did. After all, I'm new to photography, so maybe I just did something wrong.

The image in the viewfinder is very dark with the Tamron. The pictures are dark as well. Since it happened fairly suddenly, I knew that it wasn't me accidentally flipping the shutter speed waaaaaay up. Something happened without my input. The pictures are useless due to much underexposure and I can barely see though the viewfinder. The camera can't either, because it hunts constantly and rarely ever finds a focus point. I don't think this is the camera's fault, because the kit lens works fine. The viewfinder is nice and clear, the pictures are well exposed, and the focus is quick. Something wrong with the Tamron, methinks.

So, if any of you out there read this and know what I should do, please post. I'm at a loss.

[little laker]

Welcome to Pentax Forums Jester,

My guess is that your shooting in Manual, and you have the aperture way up there. Otherwise known as f-stop.

If your shooting in Automatic then it's something else.

If it's a fully manual lens adjust the dial on it to a smaller number, and you'll see the image get lighter.
Or if it's manual with an A on it turn it to the A setting, and it'll act just like your 18-55mm lens.

You'll eventually learn how to adjust those settings to suite the photography your after.

Good luck and have fun.

[nosnoop]

Check the mount and the aperture.
Is it a newer or older lens? Does it have an aperture ring? Did you put in "A"?
After you mount the lens, the aperture should be wide open, if it is not, it will give you the dark viewfinder. With the lens dismounted and in your hands, gently move the aperture lever at the lens mount to see if you can operate opening and closing of the aperture. The aperture could be stuck.

[Jester2138]

Thanks for the replies!

I tried in auto and manual, but both had the same problem. Also: when stepping up or down, there is no visible difference in the viewfinder in terms of brightness.

I took the lens off the camera and turned the aperture ring like you said, but it didn't look like the aperture was closing or opening. It just sat there while I went from f/4.0 to f/32... I would think that it should be changing quite a lot, but it isn't. Maybe I have a stuck aperture?

I don't quite understand what you mean, nosnoop, by, "After you mount the lens, the aperture should be wide open, if it is not, it will give you the dark viewfinder". Do you mean that if the ring is on A, which I always leave it on btw, and I mount it on the camera, then when I turn the camera on the f/stop should be on the widest/lowest available setting and the viewfinder bright? I did try that just to see, but the viewfinder is still dark... maybe I did it wrong.

This is a new lens. Both in my ownership and on the market I think. Here's a link to it at amazon:
Amazon.com: Tamron AF70-300mm F/4-5.6 Di LD Macro Lens with hood for Pentax DSLRCameras: Electronics

[little laker]

That lens does have a stuck aperture then
I hope that you don't have any troubles returning it.

What nosnoop means by, "After you mount the lens, the aperture should be wide open
is that if your lens has an A setting and it's on that the camera will automatically open the aperture all the way up to make focusing easier
You'll never see this until you pull the on-off switch a little past the on position while looking through the view finder.
I believe that it's called depth of field preview or something like that but I really forget.

[Jester2138]

Great...

Well, I guess I'll be sending it off to be repaired. I was having fun with that lens...

Thanks so much for the help, I really would have had no idea what to do without you!