I spoke to the Manager but I didn't push for a new lens. It has gone for repair. They were surprised by the fault but could see it, and think it could be the spring which pulls the blades closed has lost its springiness, so probably needs a new spring. They had no idea how long it would take to repair. I'll have to have a trawl through my photos to see if I've kept any that went inexplicably wrong. If I did it was probably because it was the only one I had of something which isn't going to prove much on its own.
Thanks again for your help John.

I've just had a look at my receipt. It was bought as the kit lens with my K5 on 30/08/11. Would you believe it though - the receipt is for a "Nikon" K5. Anyway when I spoke to Devon Camera Centre they said a replacement for something a couple of weeks old was probable but not for something 6 months old. I should have spotted it sooner but I kept thinking that I must be doing something wrong.

I've phoned Devon Camera's in Exeter, whom I bought it from, and they said bring it back for repair under warranty. The problem was getting worse and worse the more I used the lens while my other lenses were showing no problems at all. I was also wondering if it could have been a software problem, I'm running version 1.12 so I suppose my next step would have been to upgrade to version 1.13. I'm not particularly mechanically minded so I don't understand why the problem should be more obvious at 18mm as opposed to 135mm but I might just search the net to see if I can find any reason for that.

Thanks John,
Yes its still under warranty and thanks for helping me work it out. I'm really glad its not the camera or me.
Thank you everyone for all the help, I think you're all great

The aperture is closing on my 35mm lens, and at both ends of two other zooms (50-200 & 55-300), is also closes at the 135mm end of my 18-135 lens but not at the 18mm end.

What does that mean?

Fran

Thanks John,
I reset all the Custom functions to factory defaults this morning before I started. I've checked the Drive Mode and it is set to single frame shooting. I've pressed the +/- button and the EV compensation was set to 0.0. Does that cover all the auto-bracketing and EV options?
Fran

Mannesty, I was using Green mode because I was getting the problem in other modes and since I'm new to DLSRs and not knowing what I was doing wrong, I decided to try leaving it up to the camera - I think I was trying to eliminate "user error".

So far this morning I have tried the following:
1. Cleaned contacts with a soft cloth. There were a number of very small black particles around the rim perhaps paint or metal shavings. Removed these with cloth but made no difference.
2. Checked Av settings on screen at 135mm end of lens- all displayed OK.
3. Took jpeg shots in Manual mode, F11,ISO100,1/125 sec 18mm (the settings that gave good results in Green mode). First shot OK, subsequent shots over exposed.
4. Repeated manual mode shots in Raw. After a few I could see from the screen that they were over-exposing so on a whim I pressed the green button. The Aperture value changed to F10 and the shutter speed to 1/500 sec and subsequent 7 shots (all I took) were fine. I seem to have found a work-around, even if I haven’t a clue what’s going on.

I’ll keep investigating. If I look on the bright side, this is certainly helping me find my way around the camera.

Thanks for all your help and suggestions I will certainly follow them all through.

Thanks John, I'll try that too.

Thanks Jonathan, No to your question. I changed the metering switch to multi-segment yesterday evening. I've lost the light from that particular location so I'll have another go tomorrow. I've also got a 50-200mm lens so I'll have a go with that too.

I hope you can continue to give me the benefit of your advice. I took lots of pictures this morning using my 35mm lens and everything seemed OK. I then came home and took some using the 18-135mm lens. Things seem to be OK at the 135mm end of the lens but I'm getting some odd behavious at the 18mm end. The camera was in green mode for all of the following pictures and apart from pressing the shutter (handheld) I did nothing else.
In the first set of images below I moved the focus point from the dark open top half of the caravan door to the white bottom half on every alternate shot. The results don't appear to be consistent with this change.
In the second set of images I kept focus on the dark top half of the door. There are still discrepancies.


Images with change of focus:
[IMG]http://i1134.photobucket.com/albums/m616/Frankie174/CaravanScreenDump1.jpg[/IMG]
Images with no change of focus:
[IMG]http://i1134.photobucket.com/albums/m616/Frankie174/CaravanScreenDump2.jpg[/IMG]

Help please, is it the camera, the lens or me? Is there anything else I can do to try to work it out?