[edgara]

Will these lens fit my K20D? Vivitar 70-210 Pentax Ai Mount
Pentax Exacta MC Macro
Tamaron 70-210 Pentax Ai Mount

[marcusBMG]

hi edgara, welcome.
pentax's are great for their backward compatibility with pentax legacy lenses - best of any system. However those lenses you mention aren't for pentax. Ai is nikon. Exacta is an old camera mount. Neither will go on a pentax as is. The exacta is a hopeless cause forget it. nikon F is quite similar to pentax K but I wouldn't bother either tbh. Better to look for K mount or M42 screw mount (easily adaptable to pentax K) lenses, there are loads out there because pentax was for a while #1 manufacturer.
That last one Tamaron 70-210 Pentax Ai Mount - is a mixed description If its pentax then ok, if its Ai then as I said thats nikon. it might be an adaptall though, which has a swappable mount so that would be ok too.

[Wasp]

Pentax AI mount is a mixed metaphor. It should be Pentax K or Nikon AI. None of the lenses listed are very good in any case.

[jatrax]

As already noted none of those lenses are likely to work. And if those descriptions are from an online seller I would not under any circumstances buy from them as they clearly have no idea what they are describing.

If you are looking for lenses for your K20d stick with Pentax brand lenses not random glass that might or might not work. There are thousands of older era Pentax lenses that can be purchased for very little money.

[Wasp]

Cheap options for the K20D are the Pentax 18-55mm or 28-80mm. The F 50mm f/1.7 prime makes a good portrait lens. More modern budget primes include the 50mm f/1.8 and 35mm f/2.4.

[Kerrowdown]

Welcome to the forum from the Highlands of Scotland

[i_trax]

My favourite lens from K-20 decade was Sigma 17-70 2.8-4.5 ( ver 1 , non HSM).
I still have one , you can buy one , in good condition , for ~ AU$100.
Very versatile , a perfect walk around kit lens.

[Not a Number]

Welcome to the Forum. Any lens for Pentax should do though functionality depends on the lens. With third party lenses make sure it is a Pentax version.

You can check compatibility here (as long as it is the Pentax version):
https://www.pentaxforums.com/compatibility/

[aslyfox]

Will these lens fit my K20D? Vivitar 70-210 Pentax Ai Mount. . .

follow this link for information on Vivitar lenses which will work with Pentax

Vivitar Lenses - Pentax Lens Review Database

perhaps you can find the one you have

[archaeodude]

Welcome to the forums from the Fenlands of England!

You'll find a lot of helpful advice and friendly community members here!

[Wasp]

The easiest answer: get the genuine Pentax lens that suits your needs and budget. Can't go wrong that way.

[ChristianRock]

The lenses you should be looking for, should say "Pentax K Mount". Any lens with that mount should work with your K20D and there is plenty to pick from. Reading the reviews on this site should be a good way of picking the good from the bad - especially when it comes to third party lenses, quality can vary a lot. Usually you can't go wrong with any Pentax lens.

As for the lenses you asked about, it was already mentioned that none of them are Pentax mount and none of them will work with your camera.

[aslyfox]

if the OP made an error and meant to type Vivitar A instead of AI

there are some very good lenses which will work with Pentax

some in PK mount, some in PKA mount

Vivitar Lenses for Pentax: Zoom Lenses - Pentax Lens Review Database

Vivitar Lenses for Pentax: Prime Lenses - Pentax Lens Review Database

Vivitar, as far as I know, did not make the lenses but actually sold lenses made by other companies under their name

The Series 1 " family " had some very nice lenses

[Wasp]

The thing with third part lenses is that quality varies from outright junk to really great. You have to take it on a case by case basis, but the review section on this site is great resource for that. As long as sellers provide enough detail for you to make out what you are looking at, of course.

Stay away from old manual focus zooms. Most of them are quite poor, especially by modern standards. Using them on your K20D is going to be frustrating. Stick to auto focus zooms. The K20D is a fine piece of kit and deserves good modern AF glass.

Manual focus primes will be fine. Be warned - that particular rabbit hole goes very deep. Ask me how I know...

[edgara]

Thank you all for your advise, which I will use. Being new to Pentax, I have a lot to learn. I was brought up with Minolta SLR film cameras (3) for me and 3 for my wife, as we were heavily involved in photography, and actually started a camera club in our area. With time and age my eyesight weakened and we went tto point and shoot cameras. Now 20 years into retirement I decided to get back to good photography, and have always regarded Pentax as a manufacturer of great cameras and gear, I decided tto purchase a Pentax K100, and a K20D, and love them both. By the way I am now 80 years young and hope top do a lot of Macro Photography. Eyesight is not better , but I love the Auto focus features of these cameras. I will probably upgrade as I go along.

Thank you all for your help.