Thanks John, yes there seems to be a lot of different prices on the net. I'll get the cheaper 300mm F4 DA* then...

No I meant the two I mentioned....strange then that there's about £200 price difference between them on the net....

Slightly off-topic, but which would be a good 300mm lens for my K7? What is the difference in quality between the Pentax smc DA 300mm f/4.0 ED (IF) SDM Lens and the Pentax 300mm F4 DA* Lens?

I want to get a 300mm soon but can't decide which. Certainly can't afford what that guy is asking on ebay, but it looks a very nice lens?

The background looks fine to me too, apart from cropping out the light bit at the bottom. It's a very nice pic. If I had any comments to make, it would be that perhaps the bird could do with the darker bits being lightened a bit to bring out more detail.

I never use manual unless it's bulb, or sometimes when taking bracketed exposures (but usually just use the in-built bracketing), where I first use the Av setting with aperture set to what I want to get a starting point from the cameras light meter. Also, for panoramas I use manual, as the settings need to be the same on all the shots. Again, I get the settings in AV for an average exposure across the scene. The rest of the time I use Av, and exposure compensation where neccessary (using the histogram as reference). That way you have full control over aperture and exposure. If I see the shutter speed is too low, I open the aperture , or change the ISO. (I never use the fuction allowing the camera to set ISO) In fact, I use Av even when shutter speed is the main criteria for the picture, just opening up the aperture or changing the ISO to get the speed I need. That way, ISO is the only guesswork I need, and it's a lot easier guessing that than trying to work out the aperture, shutter speed and ISO.

Personally, I don't see the point of having a sophisticated camera with very good automatic features, and then turning it into a manual camera.

Bean-bags
Lava lamps
Geodesic domes (R. Buckminster Fuller has to get a mention somewhere)

No,it'll be 10mm...it will just look like 16mm........

Just get yourself a Sigma 10-20 and enjoy it....

A lot of lenses (including a lot of older Pentax lenses) will work on both full-frame and APS sensors. The focal length is the same, it's just the field of view that changes. There has to be a standard reference, and that is based on 35mm when it comes to crop factor.

Here's a definition of focal length (or more correctly, equivalent focal length)

In a hypothetical ‘thin’ lens (i.e. a lens that can be approximated on a ray diagram to a single plane at which refraction occurs), the focal length is the distance from the lens to the point at which a collimated beam of light entering the lens is brought to a point. In Newtonian optics this point defines the focal plane, perpendicular to the optic axis. In practice the focal length is measured from the rear nodal point, or node of emergence.As the rear nodal point is the position of the equivalent thin lens, i.e. the Newtonian lens that would produce the same effect, this distance is properly called the equivalent focal length.

All digital camera manufacturers use full-frame as the reference for focal length. On Olympus, for example, the crop factor is 2x, effectively doubling the apparent focal length. The crop factor becomes an advantage at telephoto, when the crop factor gives a field of view of a 300mm lens on an APS-sised sensor equivalent to 450mm full-frame, ie smaller lenses for the same magnification compared to full-frame.
As John says, the focal length is still 300mm, it's just that the sensor is smaller than 35mm so giving a field of view equivalent to 1.5x the focal length.