Thank you for the update, hopefully it will help others to avoid any similar pitfalls.

I agree. Everyone should use a filter from the moment they buy the lens to the moment they sell it to me on eBay.

I will then remove the filter before I start to use the nice clean lens I have just bought.....

The filter will immediately be back on eBay for the next person to put on a nice new lens!

If you want to research bubbles in optical lass then you need a treatise on the subject. This will not be for the faint hearted.

I haven't often seen bubbles in lenses, but they are quite a common thing that is not a problem. If I saw bubbles in my most expensive lens I would not be the slightest bit concerned.

If the lens did not perform properly I would be concerned, but the lens in question in this thread apparently performs well anyway.

Don't make it one of the Worried Well!

At 55mm I'm sure you can, but at 300mm (450mm equivalent!) I'm not so sure. Sharp enough maybe with a high shutter speed and maybe SR as well, but crisp means something else. That real, biting sharpness will I think still need a very sturdy tripod.

"People of older vintage," whatever can viewfinder be saying......

I always preferred black, but in the MX/ME Super days the black finish cost extra. It also wore off after a while unless treated with extreme care. Still, even a black MX with a little "brassing" looks pretty cool.

Chrome finish metal is very hard wearing, but I always thought that silver plastic looked cheap. If we have to have polycarbonate, then black is my choice.

Can you be a bit more specific please as to what is wrong with Image 1 and yet is OK in Image 2?

What is the problem you are seeing?

Both pictures are not critically sharp to my eye, but apart from camera shake and focusing issues plants move in the wind as well, so not a great subject to assess sharpness with.

If it's a focusing issue, you need to be on a tripod. Without a firm support the camera will be wavering to and fro as well as any shake issues, so not a good way to check focusing accuracy.

Bubbles in optical glass are very common and the higher the quality of the glass the more prone it becomes to bubbles forming.

There is nothing that can be done about this and it has no effect whatsoever on the image quality.

I think the images are very soft, either through inaccurate focusing or camera shake.

The DOF at f4.5 must be quite shallow as well, not helping the overall sharpness in this sort of scene.

If you have a sturdy tripod that might be a good way to go.

Well I wasn't really that shocked, only being a bit tongue-in-cheek, but...having had a good look at the Nikon D300 it didn't really inspire me in terms of handling. In terms of quality of results it's where I would head though if I had to move from Pentax.

However, I don't have to move from Pentax and I'm not really looking for anything that the K20D doesn't already deliver. Some more pixels maybe, but that's not urgent. Things seem to heave reached a plateau and from here onwards manufacturers are going to find it harder and harder to make us part with our cash.

Lenses may be the way to go, and Pentax are doing rather well at making unique and interesting optics that photographers aspire to.