[newarts]

A key concern not yet expressed is how you intend to handle and display the photos you take.

I think I'm not going too far in saying that almost certainly for daylight photos as out-of-the-camera jpegs displayed electronically it will be hard to tell the difference between the kit lens and one of the finest lenses ever made.

If you'll compromise a little on ultimately obtainable image quality (which you won't be able to see for simple photo treatments and displays anyway) the convenience of the DA 18-250 might be hard to beat.

I have the DA 18-55 & DA 55-300mm lenses and am well satisfied but I almost always use jpegs.

If you intend to push for image quality far as possible look at prime lenses; Voightlander, Zeiss, Pentax, etc. Carefully read objective reviews.

[sany]

......The PK/A adapter allows the camera to control the aperture, so the lens works like a Pentax-A lens. That means manual focus, and you'll also have to set the focal length for SR to be effective. The focus point switches to the center point only. All modes work, including P-TTL flash and multi-segment metering. ......

In practice, it is much easier to have one adapter per lens. The adapters are $80-100 for PK/A and $15-20 for P/K. My mirror lens is fixed at f8 so I use a P/K adapter there. I prefer using the other lenses with the PK/A adapter....

.... like a 35-80, 70-210 and 60-300. Look at the Adaptall lens club for examples.

Thanks Just1MoreDave, I then must look for PK/A adapter as I would like to have maximum flexibility but it looks like the adapter will be priced more than the lens.
Can you also brief what is a mirror lens please?

[Just1MoreDave]

Can you also brief what is a mirror lens please?

Instead of curved glass elements, mirror lenses use curved mirrors to gather and focus the light. The technical term is "catadioptric lens". For camera usage, they have some advantages and drawbacks. The advantages are cost, size, weight and no chromatic aberration (fringes of color caused by different light colors taking different paths through a lens). The disadvantages are a fixed aperture, less light-gathering power, a secondary mirror in the center that causes artifacts, and lower contrast.

The Tamron 55BB is 500mm and fixed at f8. It's known for having better contrast than other mirror lenses. Here is my worst photo with it. The strange background is because of the secondary mirror.



Here is one of my better photos, using the model 01F 2X teleconverter (so 1000mm, f16). With an uncluttered background, a tripod, and a bird that stayed still, it worked out much better.

[Coeurdechene]

Just my little concern is to avoid changing the lens outdoor particularly in a place where I live is dusty

be carefull but don't obsess about that...all the point in a reflex is to be able to swap lenses to get the perspective and angle of view you might want. If you got a rocket blower, handle the lenses with care, blow the dust from them before storage and put the cleaning sensor vibration on for when you power on the camera, it's very unlikely that you'll have troubles with dust (unless of course you are immersed on the fear and loath in las vegas' desert race on a daily basis). Don't obsess about dust and litle scratches. Just enjoy your equipment and handle it with care and all will be fine.
Oh and superzooms have to compromise on a lot of things to cover those insane focal lenghts...i personally prefer moderate zooms as workhorses and primes for specific purposes.

The Pk/A adapter will likely be more expensive than some adaptall lenses but that will let you use a lot of lenses,with some level of automatization (Av,Tv,Sv modes) that are usually very well priced.

A mirror or catadioptric lens is made with a two circle design...you will see like a doughnut where the glass is, that goes to a mirror that reflects on to another mirror wich is housed on the center of the doughnut wich in it's turn directs the light to the sensor. The design was used to make cheaper and more compact long telephotos (example 500mm). They produce a ring bokeh that some dislike, and that i personally love when used creatively. The tamron adaptall 500mm mirror lens is one of the few that is considered to have good IQ (there are loads of them like the centon or Samyang dirt cheap that have poor IQ).

[sany]

...The PK/A adapter allows the camera to control the aperture, so the lens works like a Pentax-A lens. That means manual focus, and you'll also have to set the focal length for SR to be effective. The focus point switches to the center point only. All modes work, including P-TTL flash and multi-segment metering. The P/K adapter and a couple of other models allow the lens to work like a Pentax-M lens, without so many nice features.

........

Just1MoreDave, from your comment above 'couple of other models' I see there are different adapters additionally to PK/A and P/K - can you please suggest an adapter that will help me handle the most features Av, Tv, (P), Manual etc.,

From your comments I guess PK/A adapter would do the trick - pls confirm and also advice me how to do the search to look for the adapter. Should I call 'PK/A adapter for K-mount or just say Adaptall adapter for K-mount?

[sany]

Just1MoreDave and Coeurdechene, I see 70-210 from adaptall 2 range being mentioned very often but when I look into the lens database there are so many different variants of 70-210 and most of their max aperture is 3.5 and above, so i am wondering which one is that which has turned favorite for so many please help.
Also, if I buy a PK/A adapter can i just simply stay assured that whichever adaptall 2 lens I buy will let me enjoy all the different modes like Av, Tv and so on...forgive me for asking so many questions just trying to make sure that i am right.

[Coeurdechene]

You should examine the https://www.pentaxforums.com/forums/lens-clubs/59769-adaptall-mount-club-tamron.html here in the forums..in there lots of people post the pictures and the precise model number. (and adaptall-2.org but i think i already posted that one in another thread)
The origina adapter will let you enjoy all your adaptall2 lenses in the same way...even if A mode wasn't fully working you shouldn't be worried you can use the green button to stop down..or do as i do, since i have some M lenses and my adaptall adapter is a cheap chinese one, just chimp and correct when you stop down the lens.
The lens database is a good source to decide between the different models too.
Enjoy (and don't worry about the questions, the people here friendly and always answer. No hassle at all)

[Just1MoreDave]

..From your comments I guess PK/A adapter would do the trick - pls confirm and also advice me how to do the search to look for the adapter. Should I call 'PK/A adapter for K-mount or just say Adaptall adapter for K-mount?

The P/KA adapter has "TAMRON P/KA JAPAN" engraved on the mount side, with three electrical contacts. The less-capable ones won't have electrical contacts, and just say "TAMRON P/K JAPAN" or maybe "TAMRON P/K-M JAPAN".

Just1MoreDave and Coeurdechene, I see 70-210 from adaptall 2 range being mentioned very often but when I look into the lens database there are so many different variants of 70-210 and most of their max aperture is 3.5 and above, so i am wondering which one is that which has turned favorite for so many please help.
Also, if I buy a PK/A adapter can i just simply stay assured that whichever adaptall 2 lens I buy will let me enjoy all the different modes like Av, Tv and so on...forgive me for asking so many questions just trying to make sure that i am right.

I'm not sure about the different zoom models. Each lens has a model number, such as the ones I mentioned in my previous post. They are engraved on the lens somewhere. Look for reviews mentioning particular model numbers.

P/KA adapters work perfectly with all Adaptall-2 lenses. I think there is some compatibility with older lenses but I don't really know for sure. There's more information in the Adaptall lens club thread.