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kezs Oct 6, 2008 10:53 PM

hello everyone,

I've been considering switching systems (currently nikon), and I've been looking into the pentax k20d. a 17-70 range would be nice, and the sigma seems to have a pretty decent one there. today, I saw that pentax makes a lens with the same range (with a constant f/4 rather than a 2.8-4.5, like the sigma). does anyone here know how they compare? is the pentax worth the price leap?

and while we're at it, I've seen everywhere that the k20d has custom settings for front/back focusing for up to 20 lenses. I know it's a way of fine-tuning the focus point (plane, rather) according to a specific lens, but exactly does that work? is it useful for new lenses?


interested_observer Oct 8, 2008 11:11 PM

Hi Kezs,

I use the K100D and not the K20 (at least not yet), so its difficult to comment on your body questions. On the other item - the DA 17-70, I may be able to shed some light on the spareness of responses here. The Pentax 17-70 lens is relatively new - being announced some time ago, but just recently available. This lens competes with a number of other Pentax offerings, the kit 18-55 (version 1 and 2), the older 16-45/f4 and the newer 16-50/f2.8. With an f4 aperture the 17-70 is in a somewhat difficult position. With most folks buying the kit (body and lens combination), they would be more inclined to go with an upgrade in lens speed to the f2.8 16-50 lens. A number of us have the older 16-45 so would probably not be inclined to another f4 lens with a slightly longer focal length.

So sorry, that there appears to not be a lot of folks that have that particular lens.

However, I would think that quite a few of us would like to hear as to why your considering switching from a Nikon to Pentax. What Nikon body are you leaving? Would this be an upgrade or a lateral switch in body capability. As you can see, especially within the lens thread, that the 16-50 has a larger set of users. One of Pentax's perceived weaknesses is the smaller selection of lenses as opposed to Nikon (since stabilization is in the body, that eliminates a whole set of lenses, and Pentax only offers auto focus lenses, as opposed to both manual and auto). So from an absolute number, it will be somewhat smaller. Plus, they tend to not have a large number of lenses that overlap one another across the various focal lengths.

Hope that helps!

bilybianca Oct 9, 2008 12:33 AM

interested_observer wrote:

One of Pentax's perceived weaknesses is the smaller selection of lenses as opposed to Nikon (since stabilization is in the body, that eliminates a whole set of lenses, and Pentax only offers auto focus lenses, as opposed to both manual and auto).

IO, i think you'll have to explain what you try to say here, I can't really follow your reasoning. No doubt that Pentax has a much smaller selection of new lenses, and that all new lenses are AF.

But how does in-body stabilization eliminate lenses? On the contrary I'd say that that is the very strong point of the Pentax system, that IS (SR with Pentax terminology)works with any lens that can be put on the body eliminating not even screw mount manual lenses from the sixties. And there is a very wide selection of lenses if you don't mind to go manual and buy second hand. Ranging from the Sigma 10-20 mm to the Pentax M 2000 mm mirror lens.


interested_observer Oct 9, 2008 9:38 AM

Hi Kjell,

Your absolutely right, I didn't explain the point too well - did I? Let me try tilting at the windmills one more time - to see if I can state the view a bit better. Well, what I was trying to say was this....

In various postings comparing other brands to Pentax, lens offering often comes up. It is pointed out that Nikon and Canon offer a very large selection of new lenses, and in comparison, Pentax has a relatively smaller number of new lenses available. So on Nikon's lens web site (for example since the OP was coming from the Nikon brand) they list 60 new lenses available. If you sub divide them into the following categories - auto focus, manual and image stabilized lenses, and make some adjustments, you gain a slightly different perspective on lens offerings between the two brands.In comparison on the Pentax web site, Pentax has 25 lenses.However in actual comparison, apples to apples, of the 60 lenses Nikon offers, 12 of them are manual, and 16 of them are VR (image stabilized). Attempting to do an like kind comparison across the lens offerings between the two brands, I am looking at it this way.....
Manual Lenses - Pentax offers the ability to turn off auto-focusing, and does not offer manual lenses. So for the sake of this comparison, remove Nikon's manual offerings from the count. Reduce Nikon's overall lens count by 12. To be fair, I believe all the brands have the ability to disable auto focusing allowing manual focusing. Also, various users prefer manual focusing lenses for applications, out of habit, or preference.

VR or Image Stabilized Lenses
- Pentax has stabilization built into the body, so that all lenses mounted are stabilized. Thus for any given focal length, Pentax does not have to offer 2 lenses - one with stabilization built in and one with out stabilization. Reduce Nikon's overall lens count by 16.
So Nikon has a total of 60 lenses currently offered. Remove the manual count of 12 and the stabilized count of 16, resulting in 32 lenses.

The point that I was trying to make - so poorly made was that in comparison of actual count Nikon when compared in this manner offers 32 new lenses to Pentax's 25. Or another way of comparison is to double Pentax's selection from 25 to 50 because all the lenses are image stabilized. Thus, from this view point, Nikon offers 60 to Pentax's 50. (Yes, I realize that quite a few will say, you do not need stabilization in the wide angle range say at 10mm.)

So rather than an absolute count of Nikon 60, Pentax 25 you can think of it as:
Nikon 32, Pentax 25
Nikon 60, Pentax 50
Actually on second thought, you need to subtract off the manual lenses (12), which leaves Nikon with 48, to Pentax's 50 autofocus body stabilized lenses
Nikon 48, Pentax 50
Now, am I happy with Pentax's current offerings of lenses? There is room for improvement. In that Hoya owns both Tokina and Pentax, there are two Tokina lenses that Pentax does not offer (the 11-16/f2.8 and the 80-400/f4) that I think would be strategic additions to Pentax's offerings. The 11-16 would extend Pentax's selection of fast lenses down to the 11mm focal length. Since Pentax and Tokina offer essentially the same lenses in the 16-50 and 50-135 f2.8, this may make a lot of sense. Also, Pentax does not have a lot of offerings above 300mm, thus the zoom out to 400mm (and its a good lens from what I have read), makes sense also. So, yes - I think that there is room for improvement in Pentax's lens selection. Also, Tokina use to offer the 80-400 with a Pentax mount, however this is no longer available.

Also, over the years - Pentax has had some very good lenses, that have been dis-continued. Bringing back these designs - I would think (updated for digital), would possibly make some sense.

Then there are the tele-converters. Pentax has 0, with Nikon offering 3. That is another weakness for Pentax.

So that was the point I was trying to make. You look at say Nikon's long list of lenses and say Wow!!! Then compare it to Pentax's relatively short list of lens, and say Ouch! However, when you compare the two, adjusting for manual and stabilization, the difference is not so large.

Did I do a better job this time around?

bilybianca Oct 9, 2008 11:57 AM

Crystal clear now, thanks a lot. And it does make the Nikon offering a little less impressing.

I do agree that there are some weak points in the Pentax line-up. Like the converter (coming, it's on the roadmap), the lack of a fast really wide (10 mm prime?) and superteles. I can seewhy Pentax are reluctant to release very expensive lenses at the long end (how many A*1200 mm f8 lenses were actually sold at around 10 000 USD?). But I'd still like to check the online store, drool over my keyboard and think "there'll besecond handones on the market before I die, yeah".

I'd love to see the FA 200 mm Macro back on the shelves too, or an updated digital version. What about a 15 mm tilt/shift lens? Ned?;)


kezs Oct 9, 2008 1:08 PM

thanks, that does help.

about leaving nikon... I currently own a d50 with the kit lens (18-55) and a tamron 70-300. I'm upgrading for image quality, both body-wise (extra resolution would come in handy, mainly) lens-wise. the kit lens is so-so outside the f/8 or f/11 apertures, and the tamron is pretty soft beyond 200mm, specially considering the lack of IS. so, because I'm upgrading both lenses, and the other accessory I have is a SB-27 speedlite which doesn't ttl with digital cameras (I also own a N65 from last century), I might as well switch systems altogether. of course nikon is still an option; they have lagged behind in a few technology upgrades, like self cleaning sensors, live-view and whatnot, but the d90 seems to have caught up with it. I'm not too fond of lens IS, though, mainly because it implies an extra cost for every lens; I know, lens IS might be more efficient occasionally, but there's still the extra cost. right now, I'm considering the k20d, the olympus e520 and the nikon d90 (in that order, maybe). I also plan to get a wider zoom, like a sigma 10-20 or similar. so, with a 3 lens set (wide zoom, a good all-around and a tele), I think I'm set, so lens selection wouldn't be an issue in any of those makers (the olympus has a great 12-60, a very good 70-300 and a very good 9-18, which gives an overall range of 18-600mm in 35mm eq.). because I'm gonna be using the main lens around 80% of the time, that's probably the most important factor in my decision. the sigma 17-70 has a very good review from the pentax 16-50 2.8 seems like an excellent choice; perhaps not quite as long as the 17-70, but with 14mp there's some room for cropping, so it's an option. like I said, my main concern is improving IQ and adding IS, at least to the general purpose and the tele lenses. about the k20d, I also like the more advanced features, like weather sealing, one-button 5 frame bracketing and a dedicated dial for metering modes...

all things considered, I know I can't go wrong, and either brand would be a considerable step-up from my current gear. so I'm currently focusing on considering what the main lens would be for each brand to help me make up my mind...

interested_observer Oct 10, 2008 12:46 AM

Hi Kezs,

You have Billy's attention here, which is good. You can rely on his opinion. The Pentax forums are very active, and extremely friendly. Everyone is very knowledgeable and helpful. There are quite a few users here that have shifted lately to the K20 body. Many are going to the set of f2.8 lenses, although the lower one appears to not be quite as wide in range as you would desire.

If you have not visited the main Pentax thread (just above this one), that would be well worth the time. danielchtong has just recently upgraded to a K20 and has been posting amazing images along with comments. Robert Barnett has just gone through a similar analysis, and its posted here...;forum_id=80

switched from Canon (I think) to the K100 then immediately to the K20. His images are amazing, well worth a look - he likes telephoto birds, and his landscapes are wonderful up in BC, Canada. He was one of the first to pick up the new DA 55-300 with which he has taken great images. The DA 55-300 appears to really be a keeper. I was able to pick one up with a bonus from work, and have been very happy with it.

Also, I was over in Hawaii in June and ran into an architect who was using Nikon to shoot birds in flight (a D70 if I remember correctly). We wound up talking and he indicated that due to Auto-focusing speed he used Nikon for birds, however a K20 for everything else - in particular landscapes and architecture due to its IQ. He also preferred the K20's color to his Nikon. Just a single sample point.

I like the wide angle end of things. Pentax does have a quality selection of wide angle zooms. Not a large selection, but it covers all of the bases. Yesterday, my Pentax DA 12-24 came, something that I have been wanting to acquire to complement my 10-17 Fisheye. These are two very good lenses. I along with several others have been toggling between the Sigma 10-20 and the DA 12-24. Monza76 opted for the DA 14mm prime. I do not know if you can go wrong with any of them.

One aspect that does set Pentax apart is their SMC coating. When compared to the Tokina lenses (essentially the same lens), the coating does make a measurable difference. A number of the Tokina lenses (the 12-24 and the 11-16) have compared very favorably with Nikon and Canon offerings.

Another aspect - one that brought you here - in body stabilization, I like very much because it applies to the wide end. In shooting in marginal environments - at sunset, it has made the difference for me, in several instances.

Also, the K20/200 pair were announced in January and available in Feb/March. If you have time, I am thinking that the K30 would be announced in January, but no guarantee. Just a thought, especially if your toggling between the new D90 and the K20.

Just some thoughts - good luck and good hunting....

kezs Oct 10, 2008 8:26 AM

hey there i_o, and once again, thanks for your reply.

it's not often to see people around here that won't try to convert you to whatever system they use, so your informative and neutral input is greatly appreciated.

coincidentally, I'm an architect as well, and I might even use whatever camera I get for an occasional work - though that's not my main objective. still, I might shoot, or try to shoot, a funny looking bird I stumble upon, and I'm curious as to what kind of difference the af'ing on a nikon represents compared to a pentax. the k20d does have 11 af points and 9 of them being cross-type, and has a continuous focusing mode, which means it can't be a bad system. besides, I my current d50 + tamron 70-300 with no internal motor means currently it's almost like I need to schedule aa focus and come back later (:-)) and that doesn't bother me very much, so I'm guessing anything will be a step up from that.

I have been checking the regular pentax forum and I like how active you guys are. I'll keep doing that in the weeks to come, when I'm making my decision, and I'll certainly let everyone know about it either way. my brother currently owns an oly e510 + a 14-42 and a 70-300 and that stuff is excellent - my point being it's all about the little differences, cause you can't go wrong shopping from the main brands.

NonEntity1 Oct 10, 2008 7:39 PM

kezs wrote:

. my brother currently owns an oly e510 + a 14-42 and a 70-300 and that stuff is excellent - my point being it's all about the little differences, cause you can't go wrong shopping from the main brands.
Hi Kezs and welcome to the Pentax forum. I don't think you will find much argument here, you can take great photos with just about any Dslr from any manufacturer. I was originally drawn to Pentax due to price. I stayed based on the image quality and, to some extent, the activity and support on this board. Thus far I have used the K100d, K10d, and K20d, the 100d and 20d are still in our inventory.

The in body stabilization is one of Pentax's best points, but another is the backwards compatability. Using an auto focus lens as a manual focus lens sucks but a good manual focus lens is a thing of joy. My macro lens is a 1980s era Kiron manufacture 105mm and it functions with my k20d just as it was designed to. My favorite portrait lens is a Tamron 180mm SP Adaptall, and it also works just as it is supposed to with the K20d.

I have a good friend who recently switched from Nikon to Canon. After viewing my macro shots he decided to buy the same lens I was using in a Canon mount, unfortunatly, it did not work with his camera at all.

The best news is that whatever system you choose will be a great system. Each system has different strengths and weaknesses but, in the end, the photographer is what makes the shot.


mtngal Oct 11, 2008 8:56 AM

A couple of your originalquestions weren't really addressed. Unfortunately, I don't have anything to add about the Pentax vs. Sigma lenses. I really haven't heard all that much about the Pentax lens - it's too new for many reviews and most of those who have been using Pentax for a while have covered the range with other lenses and aren't all that interested in it. The Sigma seems to pretty good, as I recall. I don't have either of them, I generally use the kit lens and I have the DA*50-135, which is a wonderful lens.

As far as the back/front focusing issue goes - I sure wish I had had the adjustment when I still owned a K10. Mine backfocused significantly with the DA*50-135. If I hadn't also owned a K100 and found the lens fine with it, I would have returned the lens as defective. On the other hand, the lens has been fine with the K20. It focuses slightly differently (a bit of a backfocus) compared to the 77 Ltd lens I just bought but I only noticed it when I was shooting comparison shots at 2.8. In normal shooting I don't notice it at all so haven't bothered to use the adjustment. So yes, it can be useful for new lenses.

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