This would appear to be an entirely different scenario. Your first example of two images had exactly the same exposure settings.

What you have now reported is two shots with wildly differing shutter speeds.

Any news from Mattmatic?

You're obviously closer to the sun than I am.

To qualify my "Flash is essential" statement, when you are working very close to your subject, as the OP will be with a reversed lens, more often than not (in my experience) your own body and/or camera will cast a shadow over the subject.

In those situations, flash, or some other additional lighting (reflector), is essential if you want something more than a very narrow depth of field.

My money is on the DA* 55mm 1:1.4 SDM lens. Sublime.

Flash is essential. Macro shots with anything other than minimum DOF need as much light as you can throw on the subject.

The bracket in your link looks as if it would do the job as long as you can get the flash forward enough, and it's a lot less expensive than my solution which I'm hoping will cater for all lengths of macro lens from a reversed 28mm on the body to a 180mm + bellows + tubes. My longest is the Sigma 180mm and when I add extension tubes and/or bellows, it's quite a stretch, which the Hydro Arm should cope with (I hope).

No, the bits weren't lying around, I bought them. More money than sense some might say, but I do a lot of macro work so I consider it's worth it. We all spend our disposable income in different ways I guess.

Some of the older Jessops tubes have insufficient contacts and may need some paint removed from the contact area. I have a set of Kenko tubes but I think they are quite rare now since Kenko stopped making them.

A separate power pack for the flash might be a bit overkill I think, but if you have the money, yes it'll reduce recycling time.

There are Pentax P-TTL compatible third party ring flashes from Metz and Sigma, you might like to investigate those.

For focus stacking, you'll need a macro sliding rail because ideally you need to move the whole rig, camera and flash, back and forth. Simply refocussing has a similar effect but the magnification changes slightly. You might prefer bellows instead as it is essentially a macro rail with adjustable extension for your lens.

Well your shopping list is about complete but you haven't said what your intended subject(s) are or whether you'll be taking them indoors in a studio type environment, or in the field.

Reversing rings can be had from eBay.

For flash, a ringflash is ideal but can be expensive and you'll need to make the adapter to fit the ringlight to a reversed lens. Pentax did make one but it was horribly expensive.

If you plan to use a conventional hot shoe flash, you'll need to be able to position the light/diffuser over the front of the lens and hence over the top of the subject, or thereabouts.

I'm currently constructing my next flash bracket having tried a few others that have their drawbacks. It'll consist of a CB Mini-RC (made by Custom Brackets - sourced from Warehouse Express), a Manfrotto 819-1 Hydrostatic Arm, a 1/4 female to 3/8 female tripod adapter to join the two together.

The AF540FGZ will have a Lumiquest Softbox fitted and will mount to the Hydro Arm using a Hama ball mount. The flash will be cabled back to the hotshoe to facilitate P-TTL operation but it would probably work wirelessly as well.

I'll post a photo of it when it's complete.

Given that the exposure parameters (according to the EXIF data) for each of the two pics is the same, I think the only possible cause of this is that the lens did not stop down as it should have done.

There is too little information here to be able to isolate whether it was the body, or the lens. It could have been either. Maybe you have a lens/body registration problem that could be due to a badly fitting/fitted lens.

Next step is to clean body & lens contacts and wait for it to happen again.

According to the EXIF data of your two images on Flickr, they had exactly the same exposure settings IE: 1/25th, f14, ISO 100, 0 EV comp.

That would indicate that your problem is not the same as the OP's.

Is your firmware up to date? It's showing as V1.01 but I don't know if that is the latest.

The only other variable I can think of is WB but I can't see that being the cause. WB setting is listed as 'Manual' in your EXIF.

You could compare the EXIF data of both photo's yourself in PhotoMe where you will see much more EXIF data.

I've had some feedback to the same question on another forum from Pentax users who have tried this. The bottom line is, it doesn't work very well, manual focus only, and stop down metering is a pain (we have the green button, Canon users don't).

I'm not sure I'll bother going this route.

Thanks all for your replies.

The most important part of upgrading firmware is to ensure you use a fully charged battery. It's not that it takes very long, only a couple of minutes, but if your battery dies after only one minute . . . your camera could become a doorstop.