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01-08-2011, 07:32 AM   #1
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Pentax FA 28-105mm 3.2-4.5

Hi,

I have a couple of questions about this lens.

I really like this zoom range. I did have the Sigma 28-105 2.8-4, which I liked, but I sold it, planning to buy the pentax version, as it is lighter and apparently better.

However, I have now bought two copies of this lens, and returned both. Basically, both have problems focusing - especially at the 105 end. At least 50% of the time it wouldn't focus. It would get to the point of focus, but then the focus confirmation light would flicker but fail to lock (similar to what happens if just slightly too close for a lens to focus).

I have a Pentax k-r. (Worried it was a problem with the camera - after the second dodgy one - I took the second lens into the shop where I bought the k-r and tried the lens on their K-r and a K-7, and had the same problem.)

Have I just been unlucky, or will I always have this problem with this lens?

(When replying with your experiences, can you let me know which camera you are using.)

Is it worth trying another?

Oh and the second question: are they still making this lens? The second I bought was said to be new, and I have seen websites saying this lens is a current lens, but when I phoned Pentax the guy I spoke to said this wasn't right, and he didn't understand how it could be a new lens.

01-08-2011, 07:54 AM   #2
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I have this lens and while I am generally happy with the lens I, too have experienced a focus hunting problem (albeit not as bad as bad as yours).

I started a thread a while ago but didn't manage to shed any light on the problem. I would be interested if anyone can offer some opinions.

Occasional focus issues aside my lens generally works quite well and produces good images especially stopped down a little. Even wide open the IQ is okay - a little soft but no worse than many other lenses wide open. Fortunately it is a relatively fast lens so stopping down a little still keeps its speed comparable to other kit lenses. The range makes it a great lens for candid photos of people and pets.

Last edited by Spock; 01-08-2011 at 08:09 PM.
01-08-2011, 09:48 AM   #3
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This lens is out of production as isn't of the highest quality- see the lens reviews: SMC Pentax-FA 28-105mm F3.2-4.5 AL [IF] Lens Reviews - Pentax Lens Reviews & Pentax Lens Database

The F4-5.6 version is optically better.

Adam
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01-08-2011, 10:32 AM   #4
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I have this lens and use it a lot as a walk around lens. While it's not the best focusing lens (as you've found out), I really like the colors. Mine doesn't seem to be as bad as yours. Check out my Picasa page to see if it meets your needs if you can find one that focuses to your liking.

01-08-2011, 11:01 AM   #5
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Am I right in thinking Oldschool is using the lens on the K100D and that spock is using the lens of an ist D?

Given my experience in the shop (and given I tried two lenses) I am wondering if the lens works better on the older Pentax cameras than the newer ones.

Has anyone else tried the lens on a K-r, K-x, K7 or K5?
01-08-2011, 11:04 AM   #6
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QuoteOriginally posted by Adam Quote
This lens is out of production as isn't of the highest quality- see the lens reviews: SMC Pentax-FA 28-105mm F3.2-4.5 AL [IF] Lens Reviews - Pentax Lens Reviews & Pentax Lens Database

The F4-5.6 version is optically better.
I am considering the 4-5.6 version, but it is a bit heavier than I'd like (I assume you mean the power zoom). But maybe I should stop worrying about that.
01-08-2011, 11:39 AM   #7
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It is pretty solid, but it's worth the added weight IMO.

However, why not get the DA 18-135mm? It's newer and better.

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01-08-2011, 04:30 PM - 1 Like   #8
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"Why not get the DA 18-135?"

You say that as if there is no rational reason not to get the 18-135.

If I could get any lens I wanted, without having to worry about a little difference like the fact that one costs 80ish and the other costs 550, then of course, I would get the 18-135.

"Can anyone recommend a a good 30mm prime lens for under 300?"
"Have you considered the 1000 31mm FA limited - it is honestly the best lens around."

"I'm looking for a budget camera, probably a k-x or a k-r. I mainly want it for landscape, so might consider the K10D or K20D."
"Have you considered the 645D. Okay at 10,000 it may be a bit more than you want to spend, but..."

01-08-2011, 06:04 PM   #9
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There are three Pentax 28-105s: the f3.2-4.5, an f4-5.6 without power zoom and another f4-5.6 with power zoom. I don't know which one is better optically.

I have the power zoom one, which is also the heavy one. I use it on the *ist DS and the K-7 for a lot of family stuff, nearly always with a flash. I don't have any focus issues, but I often see the focus assist light with this lens. I assumed that was because it was somewhat long and pretty slow. It does lock fine.

It's really close to the size of the DA 16-45, though heavier. I like this size lens with a flash mounted on the shoe. It seems to balance the weight better. It is a workout to use. Tack on a big hood, flash diffuser and battery grip and you would look like a pro.
01-08-2011, 06:47 PM   #10
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QuoteOriginally posted by Just1MoreDave Quote
There are three Pentax 28-105s: the f3.2-4.5, an f4-5.6 without power zoom and another f4-5.6 with power zoom. I don't know which one is better optically.
The first one was the power zoom one, the second was a rebadged Tamron, the third is the F3.2-4.5 which is the fastest and most compact and was considered the best optically. It was also the first pentax lens to have the ghostless smc coating.

QuoteOriginally posted by Adam Quote
This lens is out of production as isn't of the highest quality- see the lens reviews: SMC Pentax-FA 28-105mm F3.2-4.5 AL [IF] Lens Reviews - Pentax Lens Reviews & Pentax Lens Database

The F4-5.6 version is optically better.
It is out of production only because it was a 1990s kit lens designed for 35mm film cameras - not because it was a bad lens. On the contrary it was superior optically to all previous Pentax 28-105 lenses.

Last edited by Spock; 01-08-2011 at 08:12 PM.
01-08-2011, 07:18 PM   #11
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QuoteOriginally posted by Adam Quote
This lens is out of production as isn't of the highest quality- see the lens reviews: SMC Pentax-FA 28-105mm F3.2-4.5 AL [IF] Lens Reviews - Pentax Lens Reviews & Pentax Lens Database

The F4-5.6 version is optically better.

I most respectfully disagree. The FA28-105/f3.2-4.5 is a fantastic zoom and its compact size and internal focus are added pluses. I think it is a much better lens than its 28-105/f4-5.6 predecessors. These pics were taken with this lens. It's all in how you use it!



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01-08-2011, 08:16 PM   #12
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QuoteOriginally posted by rob_k20d Quote
I am considering the 4-5.6 version, but it is a bit heavier than I'd like (I assume you mean the power zoom).
The large and clunky Pentax and Tamron/Pentax F4-5.6 versions have absolutely no advantage over the compact and faster F3.2-4.5 version - unless you really want the original version's powerzoom feature.
01-08-2011, 08:29 PM   #13
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QuoteOriginally posted by Spock Quote
The large and clunky Pentax and Tamron/Pentax F4-5.6 versions have absolutely no advantage over the compact and faster F3.2-4.5 version - unless you really want the original version's powerzoom feature.
To be honest, the 3.2-4.5 is the lens I wanted. It is smaller, lighter, and faster, and if it is also optically superior then of course that is great too.

As I say though, I have bought two already and had to return both because of the focusing, so I am considering the power zoom as a second choice.

Of those who have used the 3.2-4.5 without any problems, are any of you using it on a k-r.

If anyone else has had luck with that combination, I may just be tempted to try again.
01-16-2011, 08:39 AM   #14
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similar finding and work around

Hi Rob, ik have similar experiences with my 3.2/18-105 (excellent IQ!, definitely the best 28-105), my 24-90 and much to my surprise incidentally even with the 17-70, tried on K20, K7 and K5. My explanation - for what its worth - is that the AF steps of these new camera's are smaller than the steps the lens can handle. Therefore the camera still sees "room for focus improvement", but the step is smaller than the lens can still make, so it starts "micro-hunting" in very small steps and the camera will not lock focus. I developed the following three different work arounds:
1. Use continuous AF and take your picture at the momentthe AF control light starts flickering:at that point the best focus the AF can get is achieving and it is normally spot on.
2. I found the problem occurs only at the long end of the zoom. I you zoom to wide and back to tele again, it usually goes well for a while, but unpredictably when, it will re-occur.
3. Touch the focussing ring lightly with one finger while autofocussing. Not so much that you block it, but just to generate a tiny bit of drag. This is usually enough to keep the lens from the "micro-hunting" I described above and it will focus lock.
01-16-2011, 06:06 PM   #15
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Yes, that would explain it. Thanks!

That would also explain why I never had a problem with the 28-105/3.2-4.5 on my old Z1 film SLR or my *istD but only noticed the issue when I used it on my K7.
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