The best, most highly spec'd camera in the world is still going to produce mediocre results if not equipped with decent (read expensive) glass and/or it's in the hands of somebody less able to take advantage of it's functions 'n features.

Even some of the most expensive lenses available for any given marque can have issues with softness at the edges wide open, colour fringing, or other aberrations.

For me, Pentax glass is unsurpassed when considering both image quality and value for money in the 'which brand and sensor format to go for' decision process.

My one disappointment is that some excellent third party lenses are no longer available in Pentax K mount.

It's good to remember that the camera/lens combination is merely a tool to record an instant in time as an image, the photographer makes that image and/or chooses the right moment to record it. There is no point in owning the best there is if you can't get the best from it.

Download a 30 day trial copy from here.

That's probably an upgrade/update version and you'd need the original CD or serial number to load it.

Easy decision, stay with the Pentax and don't be sucked into believing that full frame is better than APS-C.

Welcome Katy.

With radio triggers you can use just about any flash. The Cactus V5's work OK with Pentax cameras as far as I know, you'll need to get a handle on totally manual operation to get the best from it all though..

I would question the accuracy of that statement and would even venture to state that it is wrong.

As far as I am aware, when using P-TTL (as in TTL in the olden days), the camera does the flash metering and sets the flash accordingly.

I have taken plenty of shots with the Stofen fitted and the flash head pointing straight forward with no incorrect exposures.

Of course, if you have the flash set to A mode, that's a different matter and it is highly likely that the flash output will affect the flashes own metering.

The Stofen is probably the quickest diffuser to attach & detach. The Lumiquest can be a bit of a nightmare because it's a reasonably sized lump of plastic origami which needs to be assembled, then velcroed to the flash.

Stofen would seem the best option for you I think.

I have both K-5 and K-5 II bodies and 2 x AF500FTZ and 2 x AF540FGZ flashes.

It all works as I have stated.

Q: Which lens do you have fitted?

So, there is a problem either with your flash, or your camera. Given that you have tried two different flashes with the same result, the problem points to the camera.

First, ensure your camera firmware is up to date.

Download version 1.14 from here, then try the flash again.

Next thing to do is clean the hot shoe contacts and the flash contacts.

Try that and report back.

PS: When I tried the K-5 + AF500FTZ combination, as soon as I set the camera to M, the flash followed suit and set itself to M.

The age old policy of "if it ain't broke, don't fix it" rings true here. If you have a working, reliable Windows 7 installation that is still running at a speed you are happy with, don't upgrade to Windows 8 unless you have some really good reason to do so.

Windows 8.1 looks interesting though, especially for corporate users.

If you new PC already has Windows 8 installed, best get used to it.