[Bui]

So, I have just bought a K1ii. Do I need it? I don't think so, having been happy with a KP and a decent set of DA Limiteds + a few others DA* and so on. Do I want it? Absolutely, I'm always curious what FF looks like, and I also want to try a K1 with the 31-43-77 trio to see what all the fuss is about. Why did I buy it? Because I saw a used K1ii at an unbeatable price, and also because I have decided that the K3iii is not what I want.

In terms of lenses, I have the DA* 11-18 which you (the forum) say works in FF from 15mm. I also have the legacy A28/2, the DA* 55, the 77, and the macro 100, so I'm good. As we're heading to Christmas vacation in the mountain (after 1 month and a half under lock-down in France), we're raring to go, and of course I look forward to having new experience with my new camera. But I rarely travel without at least 1 general and WR lens (for example for the KP it would be the 16-85). So I'm looking at the 28-105. I did some research, found a few discussion in the forum, and it seems the conclusion is, it's a very good lens, and "an equivalent of the 16-85 on APSC". Wait, what? So then why should I buy this lens to walk-around a 1.5 kilograms package, to have similar quality (and even less flexibility) to the 1.2 kilograms KP + 16-85?

Or the question is, for someone owning both Pentax FF and APSC system, you buy the 28-105 because image quality of the FF combo is better (resolution, noise, etc), or because you don't want to bring 2 cameras?

[UncleVanya]

You could just take the 16-85 and use crop mode...

[jatrax]

Or the question is, for someone owning both Pentax FF and APSC system,

I use K-1II and K-3II. Depends on the situation which body I use. Sometimes one or the other, sometimes both with different lenses.

K-3II has the 16-85 on it most of the time. K-1II has the 28-105 on it quite often. The 28-105 is a very good general purpose lens. I have also the 24-70 for the K-1II but the 28-105 is so good and much lighter that I use it unless the 24-70 is needed for a specific shot.

Why both? For me I use the different formats depending on what I am shooting. I plan on having both APS-C and FF bodies so having both is not an issue for me. For many shoots having at least two bodies on site is needed just in case. When just going out with a light kit the K-3II usually goes. When going out for sunset or sunrise or other difficult times the K-1II goes. So having 16-85 and 28-105 is for me, not a duplication.

[MaineNative]

I have a K-5 with the 18-135 and the 16-85. When I bought my K-1, I also bought the DFA 28-105. If you have either of the crop lenses, the 28-105 is the full-frame equivalent. It is very sharp; as good as the 16-85. The full-frame does make a difference! I also had several lenses with 62 mm filter threads, so the DFA 28-105 works out well from that standpoint too.

I would not say the K-1 with the DFA 28-105 is too heavy. It is fairly well balanced. However, when I fly, I do tend to take my K-5 with my 18-135 instead of my K-1 because it is smaller and lighter.

I rented the DFA 15-30 and the K-1 with the 15-30 was much heavier. The 15-30 is a great lens and good for astrophotography, but it was heavy! Instead I bought a used Pentax FA 20/2.8 so I could have a light, fast wide-angle lens with auto focus. (Note: The FA 20 is not a good astro lens, but otherwise it is nice.)

For me, the step up from my K-5 to the K-1 was a big step up in night photography. Probably much less of a difference between your KP and the K-1 ii. In my opinion, the FF sensor captures much more detail. Great for stars, landscapes and city scapes.

[pentageek]

So I'm looking at the 28-105. I did some research, found a few discussion in the forum, and it seems the conclusion is, it's a very good lens, and "an equivalent of the 16-85 on APSC"

I use both lenses and I can tell you what it means: 28-105 and 16-85 are very good all-round lenses for FF and APS-C respectively. It does not mean you get similar results - sensors are different and they require different lenses. Think of following question - 'I'm looking for very good all-round lens, what do you recommend?'. The answer is: 16-85 for APS-C, or 28-105 for FF. Similarity is in function and in ways you can use them, not in the quality of an image.

[Bertrand3000]

For many shoots having at least two bodies on site is needed just in case.

Reading this I wonder: in which case you would need two bodies? Is this only because of the different sensor size? Can you elaborate?

[myrdinn]

I switched from the K5 to the K1-II. Working with the FF camera was amazing, a total difference in terms of a much better IQ. Since I own the K1-II, I haven't used the K5 anymore!
I started working with the 28-105 lens, thinking that in time I would buy another, better, lens and only using the 28-105 as a walk around lens. But up to now (I have the K1-II for almost three years) I didn't see a good reason for not using it almost all the time. It's good, sharp and not heavy. Perfect for taking photographs on the field. Only when I need a wide angle or a tele lens I remove the 28-105 from my camera, only for special occasions.

[clackers]

I think the K-1 and the 28-105 are all you need for your well-deserved mountain holiday, Bui!

[jatrax]

in which case you would need two bodies? I

For a paid shoot or for a trip that might not be easy to duplicate having a backup body (and lenses) is critical. That might be two of the same bodies for some. I have only the K-1II, K-3II and a K-01 converted to full spectrum so in my case yes, different sensor sizes but for backup purposes that is incidental. Many paid photographers simply pack two of the same body.


The other use is to have two lenses available at the same time. For example on road trips (pre-COVID) I usually had the K-3II mated to either the DA 60-250 or the DFA 150-450 and the K-1II to the DFA 24-70. So 24 to 450mm available without fumbling through a lens change.

[surfar]

To buy or not to buy the Pentax 28-105,

I bought 2,one lives on the K-1,the other with the crop kit.It works as a 40-160(rounded) on a crop body.

So its versatilty is good.

[robgski]

Do I need it?

If you like to be outdoors when the weather is bad and you do not have a weather resistant zoom lens that does not vignette (much) on a full frame, yes.
I use my 18-135mm WR on the K-1, so I haven't felt a compelling need to buy the 28-105mm

[peggers]

The DFA 28-105 is a great lens. Very quick to focus, very quiet and really good picture quality. Maybe before you rush in you might consider older lenses, that were originally made for film cameras. There are some good choices available and quite a deal cheaper than the 28-105. And, you could also consider some older primes as well because you will have plenty of cash left over to make more purchases. Having said that, I did get the dfa 28-105 myself and love it

[Alex645]

for someone owning both Pentax FF and APSC system, you buy the 28-105 because image quality of the FF combo is better (resolution, noise, etc), or because you don't want to bring 2 cameras?

Depending on how your final image will be printed or viewed, ultimately the FF 28-105mm is superior to an APS-C 16-85mm in every way except price, weight, and perhaps speed.

But ultimately the photographer will make the biggest impact on the results and if the image is not an enlargement print, massively cropped, or viewed on a 5k or 8k monitor, the difference will be small.

[DWS1]

The D FA 28-105mm is a very good lens on the K1ii. If used on the KP, it will even be better than the DA16-85mm if you can live with the focal lengths.

[northcoastgreg]

When I bought the K-1, I already had the KP and the DA 16-85 — although I wasn't really using the 16-85 all that much (I was mostly using my three limiteds, 15, 21, and 35, along with the DA 55-300 PLM). The first lens I bought for the K-1 was the DFA 28-105. I would even go so far as to say I don't think I would have considered the K-1 without the DFA 28-105. My original intention was to shoot zooms on FF and my limited primes on APS-C. That's not exactly how it worked out. When I wanted to travel light, I would take the KP and the limited primes. But that wasn't very often. More often I would take the K-1 with the DFA 28-105 and the FA 20-35 (later the DFA 15-30) and the KP with the 55-300 PLM. When I would go on longer landscape photography trips, that would the basic kit, and most of the images taken on these trips were either with the DFA 28-105 on the K-1 or with the DA 55-300 PLM on the KP. That combination has worked really well for me. It's really convenient not to have to change lenses when going from standard zoom to telephoto work. Meanwhile, I've only used the DA 16-85 once in the last three years.