I've had a look at Surfseen's picture and this is definitely not a sensor stain, it is a small fibre or hair on the sensor. It is common to get this and should be no problem to remove with a rocket blower. I would avoid giving the sensor a wet clean if possible, but if this is required I use pec pads and a wooden spatula with a flat end which I make from something like a clean lollipop stick or other similar small piece of smooth wood. Wrap the pec pad carefully around the end of the stick and moisten it slightly with isopropyl alcohol. It must not be 'wet' only 'damp'.

Pull it gently across the sensor making sure the edges are wiped. Before you do this make sure there's no dust on the sensor or you may risk scratching the surface.

This is not difficult to do, but you must be careful.

Regards
David

I don't know why everyone constantly frets/worries about 'new models' and 'discontinued models'. It is a fact of commercial business and progressive development that each model will have a very short lifespan, unless it becomes a 'cult classic' and continues for this reason, or it is cheap to make and fulfils a role in developing markets (think VW Beetle, Morris Oxford). I too have just bought a K-5. It will work exactly the same as it does now (which is very well BTW) regardless of whether Pentax replace it or not.

Stop worrying about whether or not your camera will be discontinued and concentrate on taking the best pictures you possibly can with what you have already got!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Regards
David

This thread has become really interesting. I did a test last night (not scientific of course) where I shot a still life of a porcelain ornament with my DA 16-45, both with and without a UV filter. The subject was chosen because I could control lighting and focus to be 100% identical between the two shots. Camera was mounted on a tripod, so no movement either.

Of the two shots, the one without the filter was marginally (and I do stress marginally) sharper. On the other hand, the one with the filter had less distracting reflections from the subject. Which was better? I can't say.

I think genesisphil makes a very good point above. There are situations where a filter is necessary to protect the lens, and of course situations where it enhances the picture (polariser, ND etc.). Jules makes the point about a store making more profit from filters. If anyone nowadays buys their filters this way they must need their head examining. You can get great filters for next to nothing on ebay or other online sources, so cost / profit margins do not come into the argument nowadays.

It's a matter of personal preference. I think if I was buying a used lens I would be more inclined to purchase it if I know it had been protected by a UV filter during its working lifetime. All glass needs cleaning and if you keep cleaning the front element you will scratch it.

Regards
David

I have spent a lot of time learning to know intimately the characteristics of the lenses I own. I don't have any 'exotic' ones but I do know each one inside out and therefore I know instantly which to use in a certain situation, and what aperture I need to set to make it perform in the way I wish. For example, my old 135mm SMC Takumar F3.5 is superb for portraits and still life shots, giving the colours a warmth that the modern lenses don't, whilst still being very sharp. My DA 16-45 is great for landscapes, but tends to make a mess of tree branches. The 55-300 is a fantastic all-rounder and my old Chinon 50mm F1.9 makes a good macro lens when teamed up with tubes.

Before you go and spend a fortune, get to know the lenses you have and what you can do with them. Armed with this knowledge you will know better which lenses you want to upgrade to next.

Regards
David

Keep experimenting - I suspect these were taken with the aperture wide open - you really need to stop the lens down a bit to get more depth of field. Usually F8 to F16 is viable for macro, unless you are intentionally trying to create wafer-thin DOF.

Regards
David

Absolutely glorious shots. Probably the best seen on here.

Regards
David

Number 2 is a great shot, truly outstanding.

Regards
David

I have had real problems with some polarisers that look clear / sharp when you look through them, but render focus impossible on the lens, but never with a UV and I've had a lot of these filters on a lot of lenses. I can understand that any filter, even a good UV one will have some effect on image quality, but I'd rather bear this than lose the lens. I've dropped a couple of lenses in my time that have only been saved because they had a UV filter attached which was smashed completely. Without this the front element would have been broken.

Regards
David

I can't see why a UV filter would affect the focus of a lens - it does not affect mine. Circular polariser yes - these do not work well on some lenses but a decent UV filter should not alter the focal length of a lens unless the filter is doing something it's not designed to do.

Regards
David

Put a UV filter on it. The effect on performance is virtually nil, assuming the filter is good quality and you would not thank yourself if you scratch or damage the front element.

Regards
David