Why use 'old' glass?

does the Katseye have to be shimmed or can it be dropped in as a straight replacement on a K5

Dropped in, according to Katzeye. link and it did what it said on the can for my K20

A very intersting thead. Could someone explain the difference between the various mounts? I have a K20D with a 18-55 kit lens and would like to experiment!
Thanks in advance.

your best bet is to have a read here. link

Could've just removed the images from the post...

EDIT: Not to mention two of the three were taken using a K20D.

The Pentacon 135/2.8 is widely believed to be the greatest short telephoto lens of all time; it's available in two mounts, M42 and PB (Praktica B), make sure you get the M42 variant.

Katzeye definitely needs to be shimmed.....pity they dont include some shimms with the package

Good thread. So why use old lenses?
Well I have a mix of M42 screw mount and K-mount manual prime lenses.
Reasons?

Colour rendition
Contrast or even lack of it on certain ones.
Sharpness!
tactile delight in using them
cheap
the sheer pleasure of using them
each lens have their own personality whereby they render the image slightly differently
did i mention sharpness? and price?

Get yourself an M42 to K-mount adapter, buy yourself some Takumars and then you will understand the sheer delight on using old lenses.

Oh, the first manual prime to buy is the 55mm F1.8. does not matter which "flavour" (Super-tak, SMC-Tak, auto-tak etc) the lens is the stuff of legend in the Pentax world. It is a wonderful cheap lens. You can even get it with a K-mount too. I have two.....

Oh there are others too. If you get the M42 adapter, get hold of things like the Carl Zeiss Jena 50mm F2.8 Tessar, the Helios 58mm F2 (made for russian zenits), even the wonderful but dead cheap Mamiya-Sekor 55mm F1.4. All can be found for more or less peanuts, and all are wonderful to a point that they can match the Takumars.

The Heilos 44 actually comes in K-mount as well, but it's pretty rare. The later Zenits (which used the Helios 44 as their standard lens) used K-mount, specifically on the AM, AM2 and APK.

Less rare is the MC Zenitar-K2, which is a REALLY nice lens. Looks trippy as hell though, it's rounded-off focus ring is like nothing you've ever seen before.

There's also the REALLY trippy Zenitar ME1 which has a 2-blade SQUARE aperture, designed to be electronically controlled, despite being M42.

mdc. I have never seen a K-mount Helios 44 series lens. They must be really rare.
Still the M42 one is great.

The Zenitar-K2 is something I must look out for. I might get one to have fun with.

http://www.ebay.co.uk/itm/HELIOS-44-K-4-USSR-Biotar-Lens-M42-Pentax-K-Auto-App-M...

http://www.ebay.co.uk/itm/Lens-MC-Zenitar-K2-2-50mm-Brand-New-Box-/170623811404?...

There ya go

EDIT: You can also get a Zenit 122k with Zenitar K2 for about £60.

http://www.ebay.co.uk/itm/Camera-Zenit-122k-MC-Zenitar-K2-2-50mm-s-n-97014679-Pe...

Like you say, the Zenitar is "interesting! But at least I know what it looks like

As for the Helios, the price is a bit steep, but I suppose being rare it can command that price. I think I will stick to my M42 model (must resist buying....)

Haha It's almost as weird as the Industar 50

That 122K with a lens for that price could be good. But having said that, I would rather have an MX or P60. Still for the price.......hmmmm.

I had to shim my Katzeye. It's far more sensitive than the normal screen so if you want it to work well you'll probably need to shim it.