[SpecialK]

Both, of course. No decision and second thoughts needed.

[jatrax]

15mm to be super wide on FF.

15mm field of view on FF is 110 degrees. About the same as 10mm lens on APS-C.

[Sandy Hancock]

I have both the DFA15-30 and FA31 Limited (two copies of the latter in fact), and wouldn't be without either.

BUT....if I had to choose just one it would be the 31. It's fast, small, light, and beautiful - with quintessential Pentax pixie dust thrown in. It is such a versatile focal length - wide enough for landscapes but still great for environmental portraits, and the most pleasing bokeh of any wide angle lens I have used. It also stitches really well if you want a wider view for static subjects.

[Rondec]

I would get a "normal" lens. The 24-70 would be roughly the equivalent of a 16-50 on APS-C the 28-105 would be the equivalent of a 18-70 lens. Those lenses should be plenty wide for your purposes. As far as adding on a prime, I'm not sure what to suggest there. It really depends on what focal length you like. The FA 31 is a gem, but for portraiture, I'd probably prefer the FA 77. But I'd probably wait on the prime and see what focal length you think would serve you best on full frame.

[zapp]

Thank you all! As a newcomer to this forum, really thankful for the thoughtful response. I'll research 24-70 before deciding. Also you are right I have only used a APS-C sensor cameras so really didn't expect 15mm to be super wide on FF.

I had both. Neither of these lenses makes sense on APS-C in my opinion. Both are wideangle designs for FF cameras that are overengineered for APS-C. 15-30 is a very nice lens, wide angle with zoom for FF, but it is quite big and you cannot easily fit a filter infront. Not a lens you want to take with you just in case you need more angle.
31mm has smaller filter thread, old style AF. It has special image signature, but not up to modern design standards. With APS-C I would go for the DA lenses designed for this format.
You may also consider the coming 11-18mm for APS-C for wide angle use. 100mm square filters should fit and you get a DA* lens with new specs.
24-70 is also not useful for APS-C, but great general lens on K1. 24-70 covers most focal length you really need for walking around and it dust and rain proof. For special images (on FF) I also take 77ltd with me.

[btnapa]

I need your suggestion in choosing between the two lenses.

Welcome to the forum. Having photographed my nieces and nephews at ages just born to 6 years old, I am really fond of fast lenses. It was suggested that you use the 28-105. I own that lens but it is on the slow side for indoor use. For general all purpose outdoor lens, it is fantastic. If I have to bring one lens 28-105 is it.

Back to the indoor shooting, I would recommend the 50 f1.4 or the 43 and the 77 FA limiteds. I own the last two and they are the ones I use for indoor shooting. Given that K1II is an FF camera, the 43 might be a little short for subject separation. I have used the 77 successfully as it gives me a little more space between camera and subject. 24-70 would be an ideal one lens solution for your two intended applications. The only downside of the 24-70 is that it is a BIG lens compared to the primes and even the 28-105 which is a fairly compact lens. I tried the upcoming 50mm f1.4 which would also be an ideal choice too but it is not available yet.

[Rondec]

I had both. Neither of these lenses makes sense on APS-C in my opinion. Both are wideangle designs for FF cameras that are overengineered for APS-C. 15-30 is a very nice lens, wide angle with zoom for FF, but it is quite big and you cannot easily fit a filter infront. Not a lens you want to take with you just in case you need more angle.
31mm has smaller filter thread, old style AF. It has special image signature, but not up to modern design standards. With APS-C I would go for the DA lenses designed for this format.
You may also consider the coming 11-18mm for APS-C for wide angle use. 100mm square filters should fit and you get a DA* lens with new specs.
24-70 is also not useful for APS-C, but great general lens on K1. 24-70 covers most focal length you really need for walking around and it dust and rain proof. For special images (on FF) I also take 77ltd with me.

I think the start of the thread was that he has ordered a K-1 II and so he is definitely looking at this from a full frame standpoint.

[csandeep]

Hello Pentaxians
Im jumping head first into Pentax world! I have pre-ordered a Pentax K-1II (and also in the process of selling off my Canon gear to recoup some cost). I got caught up in the moment and along with the pre-order, without much research, I'm also purchasing a Pentax D-FA 15-30mm lens.

After some careful research (aka reading this forum) I'm having second thoughts about the choice of lens as it seems heavy to carry around (mounted on the already heavy camera).

Since then I discovered the Pentax 31mm Ltd lens. Im now sitting on the fence between keeping my originally choice of 15-30mm lens or going in with the 31mm ltd lens.

I intend to take photos of my daughter (mostly indoors), her artwork (she's 4 yrs) and maybe some street photos.

I need your suggestion in choosing between the two lenses.

An update - after carefully reviewing my options I chose the Pentax FA 31mm limited lens. I received both the camera and the lens couple of days ago. Here are some shots - Pentax K-1 | Flickr