[northcoastgreg]

whereas glowing reviews of the 28-105 are probably comparing it to other consumer kit lenses

I suspect that might be just a tad unfair. The 28-105 may have aperture specs that are normally associated with consumer grade lenses, but it provides image quality that is virtually indistinguishable from professional lenses. You get the DFA 24-70 for the f2.8. If you don't need the f2.8, or can get by without it, the DFA 28-105 is clearly the better option because of significantly reduced size/weight and cost. It is the DFA 28-105 that sold me on FF. If Pentax had not produced it for their FF line-up, I'd still be shooting exclusively APS-C.

[normhead]

I suspect that might be just a tad unfair. The 28-105 may have aperture specs that are normally associated with consumer grade lenses, but it provides image quality that is virtually indistinguishable from professional lenses. You get the DFA 24-70 for the f2.8. If you don't need the f2.8, or can get by without it, the DFA 28-105 is clearly the better option because of significantly reduced size/weight and cost. It is the DFA 28-105 that sold me on FF. If Pentax had not produced it for their FF line-up, I'd still be shooting exclusively APS-C.

There will alway be a certain number of people who associate more money with better IQ. They forget however, the biggest factor in the case of these two lenses is more glass, meaning higher production costs, not necessarily better IQ on a specific image. That can be established only by blind testing couple of images from each.

In my case, I picked up a Sigma 24 macro for my K-1, a tiny lens with great performance, and for wide aperture I got the DA*55 ƒ/1.4. Add a DA 55-300 PLM and you have a light weight "does everything" kit for the K-1. You have to add a lot more size and weight to do better, and in many instances, you have to add a lot more weight and cost, for the same results.

To me, the set of DFA 15-30, DFA 24-70, And DFA* 70-200 are a fantastic pro set. As an amateur it means you have to settle for no sub ƒ/2 capability. Sub ƒ/2 can help an amateur do a lot of productive and enjoyable fooling around.

[bdery]

If Pentax had not produced it for their FF line-up, I'd still be shooting exclusively APS-C.

Before getting the 28-105, I had been using the 16-85mm and accepting the drop in resolution

They forget however, the biggest factor in the case of these two lenses is more glass, meaning higher production costs, not necessarily better IQ on a specific image.

That's true but incomplete. Amount of glass, sure, but production cost, manufacturing complexity, tolerancing and testing, R&D time and cost, etc.

[northcoastgreg]

They forget however, the biggest factor in the case of these two lenses is more glass, meaning higher production costs, not necessarily better IQ on a specific image

It's interesting to compare pro-rated f2.8 zooms with lower aperture zooms covering roughly the same focal ranges. I know landscape photographers who shoot with Nikon who swear by the Nikkor 24-70 f2.8, even though the 24-100 f4 is just as sharp comparable apertures, is less expensive, and offers a more extensive price. Is it price bias or is something that the f2.8 zooms bring to the table that the measurements are missing? I suspect it could be the latter. In addition to the DFA 28-105, I also have the DFA 15-30 — that beautiful monster of a lens. In the range these two lenses have in common (28mm to 30mm), I wouldn't be surprised if the 28-105 proved the sharper lens. But the images from the DFA 15-30, regardless of consideration or resolution, just look better. To be sure, it's a fairly subtle difference — but noticeable nonetheless. Images from the DFA 15-30 just tend to have a great clarity and richer, more deeper color than images from DFA 28-105. It's an immeasurable difference, but it's what I see when I look at images from the two lenses. So I have tended to suspect that the 2.8 lenses may in fact be "better" just because, in order to perform well at f2.8, they require not only more glass, but sometimes better glass. The DFA 15-30 contains four ED elements (opposed to one for the DFA 28-105). That can have an impact on the image quality, even if it can't be measured. So is it possible that the DFA 24-70 has better IQ than the DFA 28-105, irrespective of measurements? Sure. But from everything I've seen, the difference, assuming it even exists, is too slight to bother with given the greater great price and size/weight of the f2.8 zoom.

[Rondec]

I really think it comes down to whether or not you want/need f2.8 and 24mm. If you are doing a lot of indoor photography then having f2.8 can be really helpful. I know it is possible to get primes that cover similar focal length and are even faster than f2.8, but a zoom does provide flexibility. There is a big difference between 24mm and 28mm as well and I think that having the wide angle is pretty handy for a lot of situations.

That said, the 28-105 punches above its price range and I wouldn't hesitate to recommend it as long as you are willing to deal with the fact that it is a slower lens and doesn't go as wide (the 24-28mm range is more important to me than the 70-105mm range, but that certainly is something to consider -- it is easier to crop 70 to 105 than 28 to 24).

[RICHARD L.]

Well, last summer I found a like-new, slightly used DFA* 70-200 mm f/2.8 ED zoom for 1350 US $ here in Canada. It had an electrical problem the seller never mentioned (AF sometimes missed because of a faulty electrical contact). I got it fixed, cleaned and polished for 30 CDN $ at my trusted repairman's boutique. This lens performs in a fantastic manner and has great contrast and flare resistance despite having 19 elements. Fast f/2.8 lenses' resolution peaks earlier than slower lenses, meaning they can attain their optimum performance between f/5.6 and f/8 and they can be used in worst lighting conditions. Only problem is the bulk and the weight but I mostly shoot landscapes using a heavy tripod anyway. It is handholdable but you have to use "gun-shooting" breathing technique to get good results. Plus it can be used indifferently on a K3 or a K1.

Regards

[biz-engineer]

However, I worry I would want the 2.8 fixed aperture for low light.

Exactly.

I would have thought the 24-70 would be higher quality all around also, but that is not what I'm reading.

The 24-70 is higher quality? Yes and no.

I have both lenses. I use the DFA28-105 when weight is my primary concern (back packing or day time picture taking).

However, practically, from experience, the DFA 24-70 is actually more versatile when having a single lens:
- 28mm is often not quite as wide as I'd wish and 24mm does the trick
- f/2.8 is very useful for exposures without a tripod when the light isn't best, many times SR is good enough to get shots handheld up to the blue hour, shots you couldn't get sharp with the 28-105.

So, as you noticed, the key difference is the 24mm and f2.8, which IMO make the 24-70 a more usable lens in many situations.

Image quality wise, both lenses have their strength and weaknesses. My copy of 28-105 is sharp corner to corner from 35mm to 70mm, a bit better than my 24-70 at the same apertures, but the 24-70 has better overall rendering that the 28-105 doesn't have. Images just look better from the 24-70, due to color transmission , so anomalous glass element or whatever. I've used the 28-105 for people portraits and the colors look flat (remembers me the 18-55 on apsc), the 24-70 gives (subjective, IMO) more 3 dimensional look even at the same focal length and aperture. Also, the 28-105 is more sensitive to shutter shock at apertures from 1/30 to 1/200; the 24-70 suffer much less of this problem at the same shutter speeds.

Some people would push for the 28-105 because it's Pentax made, whereas the 24-70 is made by Tamron, but from a picture making standpoint purely as a user, I wouldn't make a choice based on who makes the lens.

Hope this helps for your choice.

---

Last edited by biz-engineer; 12-16-2021 at 09:49 AM.

[mbukal]

means those who are totally indecisive will still wait for DFA 24 (28) -105/4 ED SDM AW which will have all the qualities of DFA 24-70 / 2,8 + DFA28-105 / 3.5-5.6 with a price less than of the former and greater than the latter mentioned as well as those undecided between 70-200 / 2.8 + 70-210 / 4 who are waiting for DFA 70-320 (55-300)/ 4.5-5.6 ED SDM WR (original Pentax design) who will have all the best of both also with a price less than of the former and greater than the latter mentioned ( due to the original Pentax design and f4.5 to 200mm, of course both with internal focusing and internal zoom)

[y0chang]

means those who are totally indecisive will still wait for DFA 24 (28) -105/4 ED SDM AW which will have all the qualities of DFA 24-70 / 2,8 + DFA28-105 / 3.5-5.6 with a price less than of the former and greater than the latter mentioned as well as those undecided between 70-200 / 2.8 + 70-210 / 4 who are waiting for DFA 70-320 (55-300)/ 4.5-5.6 ED SDM WR who will have all the best of both

I really do miss a lightweight 24mm on full frame. I wish they would release the FA 24 f2 or f2.8 HD similar to the FA 35 HD, but I guess it would probably be too expensive and start crowding into the DFA 21mm

[mbukal]

I really do miss a lightweight 24mm on full frame. I wish they would release the FA 24 f2 or f2.8 HD similar to the FA 35 HD, but I guess it would probably be too expensive and start crowding into the DFA 21mm

aaa, now we’re just talking about the zooms we’re only dreaming of ( DFA 24 (28) -105/4 ED SDM AW ) and would like through the recent undefined announcement ( DFA 70-320 (55-300)/ 4.5-5.6 ED SDM WR)

[y0chang]

aaa, now we’re just talking about the zooms we’re only dreaming of ( DFA 24 (28) -105/4 ED SDM AW ) and would like through the recent undefined announcement ( DFA 70-320 (55-300)/ 4.5-5.6 ED SDM WR)

Yeah, I didn't communicate clearly enough. The reason why I want a 24mm Prime is because I have a Tamron 28-75 f2.8 zoom, and the prime would cover the wide end. Now that Pentax is planning on it, I was going to wait on getting 24-105 if it ever comes out. The 28-105mm is a great range but the more and more I shoot, the more I realize I would prefer a 24mm in my walkaround.

[normhead]

Yeah, I didn't communicate clearly enough. The reason why I want a 24mm Prime is because I have a Tamron 28-75 f2.8 zoom, and the prime would cover the wide end. Now that Pentax is planning on it, I was going to wait on getting 24-105 if it ever comes out. The 28-105mm is a great range but the more and more I shoot, the more I realize I would prefer a 24mm in my walkaround.

My response to that was a Sigma 24 2.8..... which with the DA*55 1.4 and DFA 100 macro can do about anything you might feel the DA 28-105 lacks. Throw in a DA 55-300 PLM and you can handle almost anything.

[biz-engineer]

There will alway be a certain number of people who associate more money with better IQ.

And there will always be people who find reasons for the cheaper gear to be more adequate because of the money , we know who we are

---------- Post added 17-12-21 at 22:36 ----------

To me, the set of DFA 15-30, DFA 24-70, And DFA* 70-200 are a fantastic pro set.

Yes, I think you're correct. I could do everything with those three lenses, although I have ten K mount lenses due to LBA for the most part and now I thinking to sell and keep three lenses.

As an amateur it means you have to settle for no sub ƒ/2 capability. Sub ƒ/2 can help an amateur do a lot of productive and enjoyable fooling around.

Yes, I think so.

[jab2980]

I own both. For a walk around, 28-105 no question. It's worth every cent that you'll pay for it. I've used it on multiple commercial gigs as well as extremely rare opportunities (nature photography outings to places that I may never be able to visit again and/or in rare ideal conditions). The 28-105 is equal in sharpness to the 24-70 once you stop down to f4. I use the 24-70 exclusively for event/wedding photography.

D-FA 28-105:

[Eoghan]

Don`t have the 24-70 yet so cant compare but have found the DFA 28-105 great , I also have an old Fa 28-105 F3.2 lens and it gives surprising results on my K1 , found it soft on the k3 and K5 , and this is a really small compact lens for walkaround/vacations , its just missing weather sealing and a SDM....