I'm going to buy Pentax k7. I don't know whether to buy two biscuit heads DA 2 1mm F3.2 limited DA 70mm F2.4 limited or just one 17-70.

The characteristic of Pentax really lies in fixed focus. Yincui gorge and three biscuits, as well as other LIMIDED lenses, are the brand characteristics of Pentax.

If universality is required, 17-70 is indeed better than two biscuits. Compared with 16-45, I personally think 17-70 is better, because 17-70 is a waterproof constant aperture zoom, and 16-45 can be used without water. This means that 17-70 is a waterproof system hung on K-7, which will not hinder your shooting whether it is sunny or rainy (in fact, rainy days are also a good subject, but entry-level machines or terminals can only complain in rainy days). 17-70 is suitable for both daily use and traveling (especially traveling).

While DA2 1 and DA70 are superior to 17-70 in image quality. You also mentioned the fear that you can't zoom, but that kind of worry actually only happens to users of a single fixed-focus lens. If you have two fixed-focus lenses, then this concern can actually be ignored. 2 1+70 two focal segments, basically you can use the theme of daily use on these two cookies. In photography forums such as Wuji and Hummingbird, as long as you ask, most people will recommend you to buy these two lenses. Even if you are advanced in 17-70, you may finally return to the combination of 2 1+70 (DA2 1 is close-up, scenery and street sweeping; DA70 is a portrait. My personal opinion is that you can't really enjoy Pentax without focusing. So I prefer 2 1+70. If you want a zoom lens anyway, you can consider setting up a second-hand DA 18-55WR, which is used for tourism or places with complex environment in the later period, and it is usually the bottom of the box.

Photography itself is a coin toss. If you want convenience, you have to give up the image quality. If you want to have picture quality, you must limit the subject matter. So it's up to you whether you want convenience or quality.

And the price, DA2 1 and DA70 are around 2700. 17-70WR 4200 or so. Of course, the specific price fluctuation range depends on your local situation.