That being the case, have you tried a similar experiment with the 540 mounted on the camera and set the 540 to wireless master?

That would help confirm/eliminate issues with some of the flash circuitry. If that all works, the issue will be with the onboard flash.

If, in your earlier experiment, the flash was firing every time, it clearly wasn't pushing out enough light sometimes. Does the onboard flash work consistently when NOT set to wireless mode?

You should mount the flash on the camera at least once anyway, and power up the camera and flash to synchronize the flash/camera wireless channels. Perhaps try changing the channel to see if things improve.

Interesting test with even more interesting results, and not what I would expect.

From your test results I can identify two separate issues that are probably both caused by a faulty onboard flash.

1: Sometimes the onboard flash doesn't fire at all, and
2: Sometimes when the onboard flash does fire, it fails to trigger the slave flash.

The EXIF data for the 'black' frames shows that the camera thinks that the flash did fire, in compulsory flash mode, whatever that means.

Can you say whether the flash did actually fire, but maybe much lower power?

If it didn't fire, I'd suggest your camera is faulty.

Any lens you can attach to your camera is compatible with the shake reduction (SR) system, even the 50+ year old Takumar screw thread lenses (with an adapter).

Image quality can be heavily influenced by the zoom ratio and I prefer not to buy zooms with a ratio greater than 3 or 4. That is, divide the zooms longest focal length by its shortest to determine the ratio. EG: 55-200mm has approx. 4:1 zoom ratio, 50-500mm has a ratio of 10:1.

Some of the older zooms are very good, the FA 80-320 is excellent up to about 260mm, IQ falls off a bit towards the long end.

With a limited budget, you are more or less limited to these older lenses anyway but as others have said, Tamron & Sigma lenses can be found at reasonable prices and I'm surer you'll find something that will suit you.

Finally, if you are not getting usable IQ from your kit lens I suspect you are not getting close enough to your subject. The Pentax kit lens is one of the best amongst all manufacturers and if you are able to fill the frame with your subject, you should be able to make perfectly good prints up to A3 size.

Remember your viewfinder shows only about 94% of the image that is recorded. If you exactly fill the viewfinder with your subject, when viewed on screen it will have more of the scene than you saw when you shot it. So my advice in the short term is . . . get closer.

@ Mike_P, Well you won't be needing that K7 then, will you?

Thanks Ian, but it has gone to that great lens warehouse in . . . . Watford.

It was a huge surprise to me that nobody here wanted it enough to actually buy it, especially those who complain about there being no long glass in Pentax's current lineup.

It's an affordable long and fast lens only bettered by the astronomically expensive * lenses.

I only sold it because I simply wasn't using it and I too use a T/C on my DA* 300mm with good results, but not as good as a dedicated prime.

Unless he's sold it already.

At last it has perspective correction.

Mike, don't use a rocket blower to clean the sensor on this one . . .

PS: You lucky bar steward. If only I could have logged in faster, that could have been mine. I did get a 4Gb SDHC card for £3.42 though

The Samsung 4Gb SDHC card I bought from them turned up today.