Following a recent post by Adam on FB/G+ about view finder magnifiers; I decided with my average eyesight this might be work a go.
So I ordered from eBay a KPS UMC 1.35x eyepiece. It was AU$73.70, it came from South Korea, was ordered on the 29th of December and arrived here in Canberra on the 2nd of January.

How-to.

(Sorry about the rubbish photo's, a friend has my second DSLR at the moment)
Opening the packet, you have 1 eye cup, 1 view finder, 3 mounting plates, a screwdriver, an assortment of screws, and the most useless instructions known to man.

Start by removing the standard eye piece from your camera. My K-5 is pictured here. It simply popped up and off.

Needless to say, the mounting plate that comes attached to the view finder is the Canon one. So start my undoing the two small screws on each side of the glass and remove it.

Next, take the mount marked 'Pentax - Samsung' and place it on the camera where you just removed the standard eye piece, slotting it into the groves.

Now take the new view finder and place it up against the mounting plate. You will find the two of the screws are slightly longer than the rest. I found these the easiest to use here.
With a bit of fiddling, screw the view finder to the mounting plate.

Now simply screw on the new eyepiece

Finally, switch the camera on, focus on something recognizable and re-adjust the the standard focus slider on the view finder.

Review.

Pro's: Makes the view finder significantly easier to see, which I guess is what its meant to do.
Con's: Useless instructions. Useless focus mechanism. Bit pricey for what it is.

I really cant complain about the purchasing aspect of the product. It arrived very quick, however I did pay for express postage. Compared to alternatives it was about 10-15% more expensive.
However on arrival I was a bit disappointed with what I got for $70. Mind you, I dont know what else I could have expected.
I tried to make heads or tails of the instructions, with no joy. They seem to be backwards (I think), however the installation was pretty straight forward and I was able to assemble it myself without any hassle.
The device has its own focusing abilities (in theory). By loosening off a third screw you can rotate the entire eyepiece into focus and then tighten the screw back up. The problem is that it doesn't seem to do anything at all. From all the out to all the way seemed to make no difference in the clarity of the device. *shrug*.

All in all, I'd still recommend this for anyone who doesn't have the greatest eye sight but doesn't like wearing glasses while shooting. I was still able to get enough adjustment out of the built in viewfinder focus to make the new one unnecessary.

7/10

[nanhi]

I have an old original Pentax Magnifier (do not know the model number). This is a hinged type and can be moved up and out of the way to use the viewfinder without the magnifier. But it wont fit into the K-5 eyepiece as the front metal push on insert is smaller. Perhaps there is a DIY to make it fit the K-5 eyepiece. Any help or pointers to a DIY site would be welcome.
Regards.

[excanonfd]

I have an old original Pentax Magnifier (do not know the model number). This is a hinged type and can be moved up and out of the way to use the viewfinder without the magnifier. But it wont fit into the K-5 eyepiece as the front metal push on insert is smaller. Perhaps there is a DIY to make it fit the K-5 eyepiece. Any help or pointers to a DIY site would be welcome.
Regards.

I have the same one and I have thought about dremeling the slot wider to make it fit on a Pentax DSLR but there is a set of leaf springs riveted on the inside of the metal slots which must not get damaged if the magnifier is to remain securely attached to the viewfinder. If you take the rubber eye cup from your DSLR and lay it on top of the metal, you can get a good idea how much you need to take off from each side (probably no more than 1mm from each side). I haven't done this myself, I intend to use it to shoot with film cameras because it fits perfectly on my SP1000 and has a built-in diopter adjustment which is lacking on most Pentax film bodies.

[nanhi]

Thanks Excanofd Sir, I will certainly look into your method for enlarging the magnifier slot to fit the K-5 viewfinder. Thanks also for the CAUTION on the leaf springs on either side. Yes mine too has the diopter sdjuster and a lovely genuine leather case. I will use the supplied plastic viewfinder cover to mark the amount of dremelling required w/o damaging the springs.
Evilbay sells magnifiers with removal inserts for all models of DSLRs. I might take a look to see how this attaches, for a possible DIY on my old Pentax stuff. Also can you use the viewfinder cover in some way on the Pentax magnifier - cutting out an opening and gluing it to the magnifier??
Regards.

I wrote a review of the KPS UC13 a few years back, and then submitted it to a contest as my most influential piece of gear. I don't use an eyecup at all, and this gets me a full view of the frame and the read-out at the bottom. Apart from a few imperfections and quirks (it is a generic, multi-platform device) this thing is a revelation.

The bottom line for me is... you get a full-frame view on an apsc camera. If the shipping wasn't double the price, with only one seller on ebay, it's a steal. Even for the high price, I highly recommend it, especially if you're tempted toward full-frame for the finder. (I suppose you could put it on a full-frame and get a huge view... but anyway.)