[PJ1]

one question here about the FA lens isn't F means film camera use?

The FA lenses came out in the film era (as did the F, A, M, K and all the M42 screw mount lenses). They can all be used on DSLRs. Some are very, very good and have their particular fan clubs. The important thing is that all the film era lenses cover a full frame sensor (FF) whereas the later DA lenses were designed for APS-C and generally only cover the APS-C sensor, although some DA lenses will cover the FF sensor (There is a thread about it here: DA lenses on Full Frame: Test Shots thread - PentaxForums.com ) D FA lenses are more recent and designed for use on both FF and APS-C sensors.
As your K-70 has an APS-C the distinction isn't going to worry you. There is some thought about whether lenses designed for film are as good as those designed for digital but that can get very technical. It will never worry most of us. One of our best photographers here (@kerrowdown) uses "A" series lenses exclusively on his Pentax K-1 and produces some very fine images. I still buy film era lenses but I 'cherry pick' the best of them. Check out the lens reviews here and you will see which ones have the reputations.
And keep asking questions until you are satisfied you know what you want and why!

[Adam]

thanks. I will put the fisheye on my bucket list. I did find someone asking how to compare DA 12-24 AND Sigma 8-16 on this forum. I found that thread is quite useful, too. 8-16 sounds more awesome to me - the smaller the wider you can see. lol

You might find this review helpful:

Rokinon 8mm vs. 10mm vs. Sigma 8-16mm vs. Pentax 10-17mm Ultra-wide Showdown Review - Introduction | PentaxForums.com Reviews

[CanadianKangaroo]

The FA lenses came out in the film era (as did the F, A, M, K and all the M42 screw mount lenses). They can all be used on DSLRs. Some are very, very good and have their particular fan clubs. The important thing is that all the film era lenses cover a full frame sensor (FF) whereas the later DA lenses were designed for APS-C and generally only cover the APS-C sensor, although some DA lenses will cover the FF sensor (There is a thread about it here: DA lenses on Full Frame: Test Shots thread - PentaxForums.com ) D FA lenses are more recent and designed for use on both FF and APS-C sensors.
As your K-70 has an APS-C the distinction isn't going to worry you. There is some thought about whether lenses designed for film are as good as those designed for digital but that can get very technical. It will never worry most of us. One of our best photographers here (@kerrowdown) uses "A" series lenses exclusively on his Pentax K-1 and produces some very fine images. I still buy film era lenses but I 'cherry pick' the best of them. Check out the lens reviews here and you will see which ones have the reputations.
And keep asking questions until you are satisfied you know what you want and why!

very detailed reply PJ, much appreciated. I will look into the best film lenses too. of course, have to do more study first.

---------- Post added 01-05-19 at 10:22 AM ----------

You might find this review helpful:

Rokinon 8mm vs. 10mm vs. Sigma 8-16mm vs. Pentax 10-17mm Ultra-wide Showdown Review - Introduction | PentaxForums.com Reviews

it took me a while to finish the reading but it's a Fantastic review for comparing these lenses especially with the real pictures. thanks again.

[Kerrowdown]

One of our best photographers here (@kerrowdown) uses "A" series lenses exclusively on his Pentax K-1 and produces some very fine images.

Thank you for your very complimentary comments, you've got the old Kerrowdown now blushing...

[Sandy Hancock]

Welcome! Enjoy your k-70.

As for lens choices - how deep are your pockets? As a compliment to your WR kit zoom, the DA35/2.4 and DA50/1.8 would give you extra image quality and better subject isolation for portraits at very low cost. You do miss out on quick shift manual focus, weather resistance and the build quality of Pentax's premium lenses.

If you're willing to invest more heavily into the Pentax ecosystem, the ultimate portrait lenses for crop cameras (IMHO) are the DA*55/1.4, DA70 and FA77. Only the DA*55 is weather sealed if that is important; conversely, while the DA70 is the most compact. The FA77 is my all-time favourite though - there's just something special about the way it renders; in Pentax Land we call it Pixie Dust.

For the Northern Lights, you ideally want something wide, well corrected and fast - a combination which can be be both costly and hard to find for Pentax APS-C. The soon-to-be-released DA*11-18/2.8 will probably be the ultimate package, but will be a large and expensive beast. If you're in a hurry, the DA14/2.8 is probably the front-runner in the current catalogue, but I have no personal experience with it.

Happy hunting

[normhead]

For the Northern Lights, you ideally want something wide, well corrected and fast - a combination which can be be both costly and hard to find for Pentax APS-C. The soon-to-be-released DA*11-18/2.8 will probably be the ultimate package, but will be a large and expensive beast.

If you can find a Sigma 8-16 for northern lights....