Tamron did at least one Adaptall zoom lens with built in AF that worked on MF bodies. Perhaps Pentax originally intended to have a AF lens that worked with all bodies

PNY seem OK I've got a 4GB one Class 4 or 6 (not got it to hand)
and it's actually faster than a Transcend Class 10

Any SDHC card should be OK in a K-x. 4GB or 8GB is big enough
for photos. Movies need 8GB or larger. Class 6 minimum.

I would avoid Transcend due to reported poor performance.

Someone called "iaintpayinyou" has just bought it

I'd be careful jamming or gluing anything in If it falls out it will seek out a method of supercharging your camera like you never thought possible

Helios lenses can easily taken apart and the pin held down from inside with a small piece of insulation taken from a similar diam. copper wire.

The arcade is my favourite.

I'm not sure what is the worst.....

A). Tesco's opening a supermarket in a church?

OR

B). ASDA having a Chaplin in a supermarket?

If B). is OK what would be unacceptable about Tesco's putting
a Chaplin in their Church

I don't think it matters Danny, all I'm saying is that if I have my screen set to 800 wide and my viewer set to reduce the pics to that width and the Z Key set to zoom the picture by 3x that is what I would see and they would be the equivalent views of a 315mm and 945mm lens. The view equivalent to a simulated 945mm being of acceptable quality for web use where 14.6 megapixels never get used, don't exist in the NEW file sizes and are now irrelevant. The file sizes are now just 213k and 282k. It would of course be different printing but something like Genuine Fractals could be used if needed.

You get similar situations in all photography especially with film, you take one shot and then need another a bit closer.... do you change lenses or just enlarge a shot from your current position. As long as the result is what you want you may as well just enlarge a shot rather than change lenses.

There's already quite a lot on the net about the maths involved. Personally I've not really looked into to it much, some discussions on these sites:

http://www.robsphotography.co.nz/focal-length.html

dpreview 1

dpreview 2

Dyxum

I just measured the length of the bird on my monitor on the original it was 100mm and on the enlarger 800 wide pic 300mm = 3X bigger.

Just out of curiosity I've just enlarged a shot of a bird by 3X from
a 315mm focal length lens so without doing any trig. calcs I think
that would be equivalent to a 945mm lens. I would get better results
at 100ISO and from RAW + not handheld.

Blackbird Young from last Summer (JPG file)

Full Frame 280ISO 1/125th Handheld K20D 300mm A* f/4.5 Lens 6mm Extension Tube



Approx. 3x Enlargement/Crop from JPG NOT RAW



Should be better from a K-5 as well
If I had one I don't think I could handhold a 1000mm lens

There's a lot of moaning about Pentax not doing 400mm+ lenses, but when they actually go on sale there's very little interest A few have gone though ebay and there's still a Pentax-A 400mm f5.6 in classifieds which has only had 344 views other classifieds have had 1000+

With better Camera IQ it's possible to get decent results enlarging part of the frame from a 300mm.

If you already have a 400mm there's little point in buying a 500mm because the 500mm FOV isn't a big jump from the 400mm and easily achieved by enlarging the 400mm frame.