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03-02-2019, 09:11 PM - 3 Likes   #1
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D FA28-105 vs the other 3 Pentax 28-105 lenses

The D FA28-105 has gotten generally solid praise here on the forums since its release in 2016 for the K-1. As a walk around zoom the 28-105 range has been a favorite for years as demonstrated by this being Pentax's 4th autofocus version of a 28-105 lens. In addition, Sigma made at least four models of 28-105 in the film FF autofocus days and Tamron another that is said to be the same lens as the SMC Pentax-FA 28-105mm F4-5.6 [IF].

What I can't find anywhere is a comparison across 28-105s, both current and historic, with any attention to IQ. The Sigma's are generally poorly though of in the reviews (the UC III & DG versions being the exceptions) and the Tamron's rating in the review section is significantly higher (8.54) than the same lens when rebagged as a Pentax (7.21).

The reviews of the new D FA28-105 are generally glowing with a Forum overall rating of 9.13. It has the new HD coatings (the older three are all SMC) and the lens features nine rounded diaphragm blades for smooth Bokeh. It is weather resistant, and the front element is SP coated which helps repel water drops and grease. It also has a silent DC motor but unlike older silent Pentax lenses has no provision for back-up screw-drive. It has no aperture ring, being intended solely for use on dSLRs. 92% of the 25 reviewers would recommend it to other Pentaxians. On the other hand the FA28-105 Power Zoom lens is recommended by 100% of the 21 reviewers. And at an average cost of $85 (and I know that they can be acquired far more cheaply today) versus $500 for the DFA model, the cost difference between the two could be a factor for many.

Why is it that no one really looks at the older lenses in comparison to the newer ones? There are any number of threads and posts on the forum beating the "if its new it must be better" drum. One answer may lie in a very long line of social psychology research into the impact cost has on one's perception of quality. Basically, the more one pays for something the more strongly one will defend that item and the more highly one rates it in comparison to other goods available. Very straightforward studies where the same item was given two different prices, same item, same description, same sales materials, simply different prices resulted in massively higher ratings for the higher priced item ($199 vs $19 for the same radio for example). Could this be, at least in part, a cause for the 9.13 for the new DFA 28-105 despite negative comments within the reviews that are disregarded? Could the softness in the corners for the Power Zoom FA 28-105 be more noticeable because it costs less?

When I did a little side-by-side comparison on 3 Pentax zooms at 300mm it was funny how the highest rated one was not the one most frequently chosen as the most pleasing. Could it be that the rush to buy "modern" FF lenses is just that - a rush?


Last edited by Docrwm; 03-02-2019 at 09:16 PM.
03-02-2019, 09:27 PM   #2
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There might be some comparisons in our in-depth review. When testing various FA series consumer zooms, I was thoroughly unimpressed when comparing them to the D FA.

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03-02-2019, 09:30 PM - 11 Likes   #3
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Show me comparative images or this is all conjecture.
The FA28-105 might be fantastic on the K-1, but I know the DFA is.













03-02-2019, 09:35 PM   #4
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Conjecture? It's called actually asking the question instead of assuming a position, post facto, and then defending it without consideration. Adam did do some comparisons of the FA Power Zoom to the new HD DFA. They focus on sharpness - center vs. corners - and the DFA won. I think its a bit prejudicial to call the older lenses "consumer zooms" which by implication makes the DFA a non-consumer zoom. The DFA, like the FA 28-105s before it, is the default lens on the K-1 if you order it with a lens. But it is clear, if you pixel peep then the DFA may be less irritating to you. Frankly, the only time that level of resolution is important to me is when I'm doing macro shots.


Last edited by Docrwm; 03-02-2019 at 09:46 PM.
03-02-2019, 09:51 PM   #5
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Your final question is pure conjecture. If you care about the question, do the experiment. I await the results with baited breath.

The results will have to be dramatically better than my snapshots to outweigh the weather sealing, quick shift and silent autofocus.

And who said the DFA28-105 isn't a consumer zoom? I'd go so far as calling the kit zoom. It's still awesome though.
03-03-2019, 12:48 AM   #6
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QuoteOriginally posted by Docrwm Quote
Could it be that the rush to buy "modern" FF lenses is just that - a rush?
It's not a rush, it's a short cut that works 99% of the times. The DFA28-105 is not an expensive lens relative to it's category, it has modern coatings, quick AF, it is supported by camera firmware, it is available of the shelf, and when you buy it you get the return policy and 1 or 2 years warranted. When you buy the DFA28-105 if it doesn't work you can return it and get a new one, with an old lens model of this kind if the lens fails to focus the cost if for you. If you have plenty of time but no money, you could do the complete side by side comparison of every detail between the DFA28105 and older lens models, save a few hundred dollars if you can find the old model for sale in good shape and reasonable price.
03-03-2019, 02:34 AM   #7
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QuoteOriginally posted by biz-engineer Quote
It's not a rush, it's a short cut that works 99% of the times. The DFA28-105 is not an expensive lens relative to it's category, it has modern coatings, quick AF, it is supported by camera firmware, it is available of the shelf, and when you buy it you get the return policy and 1 or 2 years warranted. When you buy the DFA28-105 if it doesn't work you can return it and get a new one, with an old lens model of this kind if the lens fails to focus the cost if for you. If you have plenty of time but no money, you could do the complete side by side comparison of every detail between the DFA28105 and older lens models, save a few hundred dollars if you can find the old model for sale in good shape and reasonable price.
Assuming the image quality of the FA 28-105 was identical to the DFA. I'd personally still have dropped the $350 I paid for it because I wanted a weather sealed zoom.

Unfortunately that's an issue with the older lenses or third party lenses. Even if all things are equal, if you want a sealed system, all things aren't equal.



03-03-2019, 02:38 AM - 2 Likes   #8
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QuoteOriginally posted by Sandy Hancock Quote
Show me comparative images or this is all conjecture.
The FA28-105 might be fantastic on the K-1, but I know the DFA is.
Outstanding results in conditions where WR is so useful, Sandy!

03-03-2019, 04:56 AM - 1 Like   #9
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QuoteOriginally posted by Docrwm Quote
Could it be that the rush to buy "modern" FF lenses is just that - a rush?
which benefits us much-later-adopters by picking up used bargains as they sell off perfectly good lenses to grab 'modern' glass....
03-03-2019, 04:56 AM   #10
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I'm going to jump in with both feet: The FA PZ 28-80 & 28-105 get undeserved low reviews in my opinion. They weren't 'kit' lenses (there was no discount if bought with a Z-1 you paid for the body and the lens). Later FA zooms (IIRC the silver versions - possibly without PZ) were kit lenses (a body and silver 28-80 cost 20 more than the body only). The PZ zooms are not the best finished lenses, they're heavy (for their time), the focus & zoom rings aren't the smoothest and the PZ switch is prone to breaking.

When originally reviewed, the 28-80 was considered a good zoom and the 28-105 better. I bought the 28-80 (couldn't afford the 28-105 and Z-1) and shot loads of Kodachrome 25 with it without any problems. I should do a test (I have two 28-80s and two 28-105s) - I've done a brief test with a 28-80 on my K-5 but not K-1.
03-03-2019, 05:34 AM   #11
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Depends on the situation. For someone having broken his/her left hand, the power zoom feature of the FA28-105 PZ allow to still be able to use the camera with the right hand only.
03-03-2019, 06:01 AM   #12
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If you were comparing something like the D FA 50m 1.4 and older FA alternatives, then I think this would be a valid comparison and worthwhile to make ..... But between the D FA 28-105 and it's ancestors then I doubt this is a worthwhile exercise.....

I mean for the money its a no brainer, and probably not worth the effort to try and find the older options? I certainly didn't bother when I had the option to buy new at a discount. Should I have?
03-03-2019, 06:04 AM - 1 Like   #13
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If you're looking for some opinions of the older 28-105 glass go here Stan's Pentax Photography
Old site and opinions only. I run the FA 28-105 IF version and it's a decent lens. Love the colors produced.
03-03-2019, 06:06 AM - 1 Like   #14
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QuoteOriginally posted by Docrwm Quote
Pentax's 4th autofocus version of a 28-105 lens
Pre-AF, let's not also forget lenses like the Pentax A 35-105 f3.5. It's generally well regarded around here, and has great sharpness and rendition.

My only gripe about the current DFA 28-105 is that it isn't a constant f4. But I have no issues with it's optical performance.
03-03-2019, 06:51 AM - 3 Likes   #15
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QuoteOriginally posted by rawr Quote
Pre-AF, let's not also forget lenses like the Pentax A 35-105 f3.5. It's generally well regarded around here, and has great sharpness and rendition.

My only gripe about the current DFA 28-105 is that it isn't a constant f4. But I have no issues with it's optical performance.
One person's complaint is another person's joy. All a constant aperture means is you slowed down the wide end to the same as the long end. You have enough glass for a wider aperture but you cripple the lens. Variable aperture is a more efficient use of glass.

I wasn't happy with my K-1 until I purchased the 28-105....
None of my older FA or F lenses comes close.

When a lens is expensive I can see looking for alternatives. Looking at the DFA 70-200 the tamron 70-200 has a lot going for it. I'm not sure that for a lens the price of the DFA 28-105, you should be looking for alternatives. If you do go for an alternative, it will be for price, not performance or IQ, and that isn't changed by comparisons. You don't need an expert opinion to decide which is more expensive.

The DFA 28-105 has WR and silent AF. Those two things alone mean I'm not interested in the others. But if I see something at a garage sale for cheap, I might give one try.

Last edited by normhead; 03-03-2019 at 08:47 AM.
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