I don't have an MZ50, but I THINK the answer is this:
You can use non-A lenses (ie K & M and certain third-party lenses) only at full aperture, because the camera can't stop the lens down properly at the instant of taking the picture.
What I think you CAN do is use most screw-mount lenses with the K adaptor. These lenses generally have a button on the side which enables you to stop down to the selected aperture for metering (on the Spotmatic and earlier cameras), then open up again for focussing.
You will have to do it the other way around. Focus, then stop the lens down manually before you take the picture.
I have been doing this successfully with my *ist D using an old 55mm SMC Takumar. It's a bit of a nuisance, but in bright light it works well enough.
There are a great many old screw-mount Takumars for sale, and they usually don't cost very much. These were amongst the best lenses of their time, and if you buy SMC Takumars they might well be as good as anything you can buy new today.
By the way, I don't think it was a lack of courtesy that stopped people replying, just a lack of knowledge. I'm not confident I'm right either! Why not go to a camera shop and ask to try a second-hand M lens on your camera.

If you want an answer, could I suggest you tell people which camera you are using.

Do you think that it might help us to help you if you describe what is going wrong? Or do you think we can simply guess?

Well, you may be right. Probably 99% of reported DSLR camera problems are down to user error, and I suspect the same cause here.

Post some pictures that you think are not up to scratch and we'll see if we can tell you what you are doing wrong. Don't do anything to the pictures other than reduce the size so that the bottom edge is 600 pixels, or thereabouts.

If you don't know how to do that, download IrfanView (it's free, at http://www.irfanview.com ) and go into Resize on the Image menu. Then type 600 into the Width box under "Set new size", and press OK. Then save the result under a new name. When you install Irfanview, make it the default for image files, unless you have a good reason not to.

And make sure you are using good, fully charged, batteries in the camera. NiMH batteries are best. I presume you are using the original 18-35mm lens?

The *ist D is a splendid camera, capable of superb results in the right hands, and generally very reliable.

G

PS: Are you printing your pictures straight from the camera, or are you trying to edit them first?

My device is a Jessops PCMCIA Compact Flash reader.

No suggestions, I'm afraid, for a cure, but, if you can't get it to work, there are various card-readers that will plug into a pc or a laptop. Many people find these easier to use anyway than plugging the camera into the computer, which ties up the camera and uses battery power.
My card reader, for a laptop, cost less than £10.00.

I should ask Pentax if they have spares for this; you never know, they might.
Alternatively, you could cannibalise a part from a non-working or cheap gun.
Looking at my flash guns, the AF240FT has a rather different mount, without screws, so it's no good. However, the AF240Z and AF200S both look as if they might work, though you would need to make another hole because they have 3 pins rather than 4.
Keep a look out on Ebay for old flash guns.

George

Lenses for Asahi Pentax 35mm cameras have only ever been made in two mounts.

The first type, from 1957 to 1975, was the Pentax 42mm screw-mount, and the second type is the Pentax K (or PK) bayonet mount.

All the K bayonet lenses will fit your camera, even those made by companies like Ricoh and Chinon.

Generally speaking, it is a good idea to buy Pentax lenses (they're usually better made and better optically), and there are plenty available second-hand on Ebay at low prices. The super-multi-coated ones are best, and they are identified by having "SMC" in the name of the lens.

Most second-hand Pentax bayonet lenses are "M" series lenses, which will work fine, but only in aperture priority or full manual modes. They are manual focus. A typical wide-angle lens will be called "SMC Pentax-M 1:2.8 28mm.

Next up are the "A" series lenses, which work in all exposure modes, and are also manual focus. These lenses will be called "SMC Pentax-A.....")

There are two varieties of auto-focus lenses, the "F" series and the "FA" series. (eg: "SMC Pentax-F....").

If you come across a lens without one of these letters to indicate the series (eg: "SMC Pentax 1:2.8 28mm"), it will be one of the earliest bayonet lenses, and usually of very high quality (and correspondingly high price).

The first of the numbers after Pentax-M, or whatever, indicates the maximum aperture of the lens. Anything under 1:2 is considered "fast"; in other words it will allow the camera to take a picture in quite low light. The second number or numbers indicates the focal length. The focal length determines the angle of view, and a 50mm focal length is roughly equivalent to the angle of view of the human eye.

Fixed focal length lenses are generally smaller, lighter, optically superior, faster, and cheaper than zoom lenses, but of course zooms are more convenient. (Zooms are lenses where the angle of view is adjustable.) A typical auto-focus zoom would be the SMC Pentax-FA 1:3.5-5.6 28-80mm. Note that the maximum aperture varies as well as the focal length.

As new Pentax lenses are usually very expensive, you will probably be looking for a second-hand lens.

Before auto-focus became popular, zoom lenses were rare and expensive. Most lenses were "primes" (meaning they had a fixed focal length). This means that on the second-hand market there are lots of good manual-focus prime lenses, and relatively few auto-focus zooms.

A good choice for a wide-angle lens would be 28mm, and they are available in maximum apertures of 1:2, 1:2.8 and 1:3.5. The last one is generally considered the best optically, but the 1:2.8 is more common and can be used in lower light.

Lenses with a higher focal length than 50mm are called telephotos, and a good choice for many people is the SMC Pentax-M 1:3.5 135mm.

If you are determined to get an auto-focus zoom, then the SMC Pentax-F 1:4-5.6 70-210mm is considered pretty good, and is fairly common and reasonably cheap. Avoid the 70-200mm.

Here are two good links:

http://www.bdimitrov.de/kmp/
http://stans-photography.info/

Hope this helped.

George

Although the Pentax f3.8-5.6 28-200mm lens is made by Tamron, it is given the Pentax SMC coating (unlike the Tamron-branded version). If the Promaster is basically the same lens, it still won't have the Pentax coating, so will be inferior as regards flare, contrast, and colour.

Ask if you can use flash. The answer will probably be NO. If so, ask if you can check the lighting during a dress rehearsal. Then you'll know what speed film you'll need. It'll be fast, you can bet that!.