Cosina 100-400 on 400d

[bend the light]

Hi all,

I bought a lens in a charity shop. Knew it was cheap and cheerful, but thought it would do me ok as a long lens for birding when I'm in Wales during the holidays (going to visit the red Kite centre, for one).

The lens is a Cosina 100-400 f4.5-6.7. Push and pull to zoom. But, I have a problem...

I can focus, autofocus works, and the zoom works well, and I can take a shot when on manual focus. But when I swithc to autofocus, it does the focussing, but then doesn't take the photo. The shutter won't go! The focus confirmation light (green dot on bottom right of viewfinder) flashes slowly when the shutter is depressed, but no shutter actuation.

anyone had any issues like this? Is it Cosina? I don't get the Err99 that you sometimes get with non-genuine lenses on the 400d, so it's not that...

[bend the light]

Well, I went outside, found a decent edge, opened the aperture rigt up, and it takes a shot, but only with very slo shutter.
Checked the aperture by closing it down, and then with the DoF preview, and it MADE NO DIFFERENCE. Did the same thing with the 75-300 canon lens, and the aperture closing can be seen clearly when the DoF preview is pressed. So, conclusion, the aperture is not being controlled. It is closed down at f22 (minimum, I think) and doesn't respond when changed on the camera. So, either a communication fault, the lens is not compatible, or there's a mechanical fault with the aperture blades. Any which way, it don't work!

[miketoll]

Bad luck. My guess would be the aperture blades. Charity shop or not they still should sell an item that is fit for purpose so you should be able to take it back for a refund.

[bend the light]

True, Mike, but it's 100 miles away! May be able to get my mum to take it back...her caravan is nearby.

[postcardcv]

Originally Posted by miketoll

Bad luck. My guess would be the aperture blades. Charity shop or not they still should sell an item that is fit for purpose so you should be able to take it back for a refund.

that's a tricky one - if the charity shop was selling it as a fully functioning lens then I guess it could be returned, but I guess if ask they would have said that it was sold as seen. Personally I don't think I could bring myself to take something like that back to a charity shop.

I'd be intereted to know how much was paid for it, if it was cheap enough I would buy it as I would quite like to get my hands on a dead lens to try something with...

[bend the light]

Originally Posted by postcardcv

that's a tricky one - if the charity shop was selling it as a fully functioning lens then I guess it could be returned, but I guess if ask they would have said that it was sold as seen. Personally I don't think I could bring myself to take something like that back to a charity shop.

I'd be intereted to know how much was paid for it, if it was cheap enough I would buy it as I would quite like to get my hands on a dead lens to try something with...

How cheap is cheap.

I paid £40 for it...

Not sure I would take it back...might fleabay it.

I'll put the money to my 50mm f1.8 that I need in a months time.