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07-23-2009, 09:02 AM   #1
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Pentax K-M Zoom Lens needed

I just bought a pentax K-m. I'm a long time K1000 user, which I sold a little over a year ago when I moved across the world. My father had one before I was born, so I've had lots of manual experience..but.. not in awhile. I hadn't really picked up the k1000 in a few years since I went digital. I finally got myself a DSLR so I can start caring about that stuff again, so I bought this camera about a month ago.

Last year during hockey season I was taking some shots with a kodak z740, not an impressive camera, but it does have a nice 10x optical zoom on it, which was good for getting reasonable shots of what was going on on the ice without feeling like I was sitting in the next building.

The kit lens that came with the K-M is sufficient for me now for day to day use (the 18-55) but to be honest I don't really find that it has much "zoom" compared to the z740.

So in the next 3 months or so i'd like to find something better and get it. So I'm looking for recommendations. I've had a little trouble finding zoomed in and out comparisons of pentax lenses and I'm not familiar enough with the technical stuff to look at something like a 50-200 and figure out how that roughly translates to what I was getting with the kodak.

I'm not a pro, so I don't need a ridiculously expensive lens, frankly since its going to be my first zoom lens, I'd take a recommendation for a reasonable 3rd party lens if there are some savings or what not. I'm comfortable focusing and setting the fstops myself, so even if it is a non-digital lens that is fine with me. I should mention that in Korea, I'm not sure if I'll have access to the full range of stuff, but I have noticed "Tamron" for sale here which I saw mentioned in conjunction with a user review of pentax, and of course there seems to be genuine pentax lenses here as well, but I'm not sure how the price compares to back home.


Any help is greatly appreciated.

07-23-2009, 09:27 AM   #2
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Depends on how much zoom you need. The general rule with Pentax DSLRs is that the lens are equivalent to 1.5 times the focal length. I find that Tamron makes very good zoom lens for Pentax DSLRs. I have a fast standard zoom lens, the Tamron XR Di 28-75mm f2.8 lens which was a great first time lens. New lenses are getting expensive, so a gently used lens will be a cheaper route to go.
07-23-2009, 09:45 AM   #3
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Well, I guess I'd like as much zoom or close to as I got with the Kodak. As a non SLR they put their zoom as an X factor and not in mm, so I'm not sure exactly what the zoom is. 10x, and one website lists it as 38-380mm equiv. I've been looking at a couple Tamron lenses on a shopping site here in korea which don't have bad prices.
One is the AF70-300mm F4-5.6
the other is AF100-300mm f5-6.3 (I'm trying to decipher the korean to find out if this mounts a pentax, they specifically list canon and nikon separately)

The AF70-300mm is reviewed here and there are some complaints (And evidence) of CA, but overall for the price it seems nice.

The AF100-300 I found on another site mentions it is "slow" I guess that means I need to leave the shutter open for it..which I'm guessing might not be that good at a hockey game. It does suggest that with a digital camera its the equivalant of 465mm.. I'm not sure how that works to be honest.

am I going to find a zoom lens in the price range of these two that would be sufficient for light to medium action in artificial light or am I dreaming?
07-23-2009, 10:23 AM   #4
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The Kodak Z740's lens is (sort of) like a 38-380mm lens would be on 35mm film. On the K-M, the range translates to 25-250mm. This comparison starts to fall apart if we're talking about other lens qualities like speed or depth of field or final image quality, but for just comparing focal range, it works.

Four popular choices come to mind: Sigma and Tamron make 70-300mm f4-5.6 lenses that are inexpensive, even a bit less than the Pentax 50-200mm. They have decent optical quality and should do the job for you. Pentax has a competitor to these lenses, the DA 55-300mm f4-5.8, which has better optical quality but a better price. They also have a one-lens option, the DA 18-250mm f3.5-6.3, the most expensive of this group.

At the telephoto end, the difference between 200, 250 and 300mm sounds like a big deal but it's not that big. In fact, all of these lenses don't go to 300mm unless they are focused at infinity. So you might consider an old 70-200mm or so manual focus lens as an option. One of the best is the Pentax-A 70-210mm f4. The completely manual Vivitar Series 1 70-210mm f3.5 is another option. That range was very popular on film so there are many options. The two lenses I've mentioned let in a lot more light than any of the above four lenses, so they would allow a greater range of photos in low light. You can always crop a bit to simulate a greater zoom range, but adding extra light is harder.

07-23-2009, 10:24 AM   #5
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Tamron 70-300mm lens for the price is a great deal. Your other options, and check the lens review forum on this site, are Sigma 70-200mm lens with a faster aperature (more expensive) and the Pentax telephoto lens you already mentioned. I use my Tamron 70-300 for tennis action and when mounted on a tripod outside, it works well.

Your other option is to buy a fixed lens 300mm lens which may have a faster aperature .
Good luck in your search.
07-23-2009, 02:59 PM   #6
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Plus don't forget the crop factor for the APS-C DSLR that you are using which is 1.5X so your kodak equivalent of 380mm would be a 250mm lens.
So, I guess a 300mm lens would more than suffice for what you are looking for as a 300mm lens would translate to 450mm.
If you couple in a TC (teleconverter) which is either 1.5X or 2X then you can still multiply that 450mm to a longer focal length!
07-24-2009, 04:59 AM   #7
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Thanks for the input guys. I really appreciate. A couple questions...
I don't suppose anyone would have a couple comparison pictures of the zoom from say 300mm and 450mm equivalent (200mm and 300mm respectively)?
I just noticed that the Pentax DA 50-200mm is only a few dollars more than the Tamron 100-300mm, and around the same price as the Tamron 70-300mm and I'm wondering if anyone could comment on that comparison.

I realize I'll get more zoom with the Tamron, but how about speed? Is the pentax any faster of a lens than the Tamron?
How about the CA between the three lenses? I saw a sample pic from one of the tamrons (maybe the 70-300) which showed some significant purple where some branches were sitting in snow, and I thought that if I get some black uniformed hockey players skating on white ice, I might have some CA problems.

I was hoping one of them would be significantly cheaper, but all sitting within about $20 of each other..so price I guess isn't a factor. Has anyone used all 3 of these or at least the pentax and one of the tamrons?
07-24-2009, 10:24 AM   #8
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A couple of things:

The 18-55 is most likely a much "better" lens than the one on the Kodak. In general, the higher the "X" factor on the zoom, the worse the quality, all else eqal. So you generally sacrifice image quality to get larger zoom range. This is less of an issue with the lenses for smaller sensor cameras like your typical P&S, but it becomes more of an issue for lenses for larger sensor cameras like a DSLR. So instead of searching out one lens with a higher "X" factor, the best quality would generally be to get a lens that you'd use *in addition to* your current lens, one that starts where your current lens leaves off. Choices include the Pentax DA50-200, DA55-300, DA*60-250, and various other third party options. You'd switch between that and your current lens depending on whether you wanted long or wide.

But there are also perfectly good lenses that do have higher "X" factors than your current lens and do both wide and long. The obvious/common/popular chocie would be the Tamron, Pentax, or Sigma 18-250.

As for "X" versus mm, the "X" factor is actually a pretty misleading and vague way of describing things. The focal length in mm is what really tells the story of what kind of picture the lens takes. The longer the focal length in mm, the bigger it makes things. A zoom lens is one that covers a range of different focal lengths, from short to long. All the "X" factor does is divide the largest focal length by the smallest. So an 18-55 is 55mm at the long end, 18mm at the short end, which works out to 3X. But then, a 100-300mm lens would *also* be 3X, and would yield *MUCH more magnification, but would be completely useless for the wide end). So comparing focal lengths, not "X" factors, is the only way to know what's what. Unfortunately, the same focal lengths mean something different form one camera to the next in terms of how big it makes things appear, so that's why you'll see focal lengths listed a "35mm equivalent", which means they translate the actual focal length to the corresponding on on a 35mm film camera (and the "mm" in "35mm" is not a focal length; it's the size of the film).

As people are explaining, to convert to 35mm equivalent on a Pentax DSLR, you multiply by 1.5. So an 18-250 is 27-375. You'll have to consult the specs for your Kodak to see what it's focal lengths actually are (it's normally printed on the front of the lens) and how that relates to 35mm equivalent. I'll guess that 10X lens is either 28-280 or 35-350. Either way, at 27-375 in 35mm equivalent, the 18-250 would actually be longer than your Kodak. The DA50-200 at 75-300 in 35mm equivalent would be similar at the long end.

07-25-2009, 08:24 AM   #9
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I'm not planning on replacing the 18-55, I'm planning to use the zoom in addition to that, mainly at the hockey rink, but probably outside that as well from time to time, so I'm not really that concerned about getting something that goes wide like an 18-250.

The Kodak says it is a 38-380mm equivalent, that is all it says on it. The website isn't much more helpful: 38–380 mm (35 mm equivalent) KODAK EASYSHARE Z740 Zoom Digital Camera Specifications

I've pretty much settled between either of the two tamrons, or the pentax lens, they are all within the price range I'm looking at. I'm just looking now for some opinion of which people think are going to be better quality. The 200mm might come up a tad short against the kodak (even when adjusted) but yes I expect the quality will be a bit better. I'm wondering if the quality of shots (clarity, speed, CA) would be significantly different in the Pentax compared to the two tamrons? Thinking like an amateur and not a professional.

As an example, this image was resized, but not lightened. It is at a distance of around 20-25 meters in the rink. The lighting is not bad, but the kodak couldn't compensate fully for it. Detail is about what I'm looking for,



This is one is at a distance of 35 meters, full zoom, it has been lightened (Paint shop pro 9.0 autofix) and resized.



I'm sure to get significantly better quality I'd have to spend a bundle, but I'm hoping with the better camera, and one of these lenses I could get better than that. At the least I'm hoping the better camera will let me run a slightly faster shutter speed in those situations so as to get a better freeze on some of the action when it happens.

Last edited by crossmr; 07-25-2009 at 08:50 AM.
07-25-2009, 11:29 AM   #10
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QuoteOriginally posted by crossmr Quote
The Kodak says it is a 38-380mm equivalent, that is all it says on it. The website isn't much more helpful: 38380 mm (35 mm equivalent)
You don't need any more help than that, then. Now that you know it is 380mm in 35mm equivalent, you know that you need 380/1.5, or around 250mm, to mimic its field of view on your DSLR. 200mm is "almost" 250mm and you're unlikely to be disappointed with it being much less; similarly, 300mm is only slightly longer than 250mm and you are unlikely to be impressed with it being much more. So pretty any of the zooms being discussed would be fair game.

QuoteQuote:
I'm just looking now for some opinion of which people think are going to be better quality.
I think it's pretty much universally agreed the Pentax DA55-300 is the best of the bunch, as it should be considering it costs quite a bit more than the others. But the others are all very good too.

QuoteQuote:
I'm wondering if the quality of shots (clarity, speed, CA) would be significantly different in the Pentax compared to the two tamrons?
The Tamron 70-300 is infamous for having about the worst purple fringing (a form of CA) of any lens ever, at least when shooting a high contrast subject like a light very dark or very light object seen against the sky. Aside from that, really, these lenses are all pretty good. Personally, I'd be choosing based on price, size/weight, focus speed, presence of quick shift, anything else really.

QuoteQuote:
I'm sure to get significantly better quality I'd have to spend a bundle, but I'm hoping with the better camera, and one of these lenses I could get better than that. At the least I'm hoping the better camera will let me run a slightly faster shutter speed in those situations so as to get a better freeze on some of the action when it happens.
Unfortunately, none of the lenses being discussed are "fast" lenses - meaning they don't have a particularly large maximum aperture. They are all f/5.6 or worse at the long end. Meaning you will still struggle getting fast enough shutter speeds. Lenses that go to f/2.8 or so are what you want for indoor sports, but they are *MUCH* more expensive, and gigantic compared to the ones you are looking at. So realistically, you'll still struggle trying to shoot action in low light. but at least the DSLR will perform better a higher ISO than your Kodak.

Typical lenses for sport would include the Sigma or Tamron 70-200, or the Pentax 50-135. or you could go cheap and pick up a used manual focus 135 for well under $100 and play around with that.
07-25-2009, 06:24 PM   #11
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Unfortunately the 55-300 is out of my price range. The 50-200 is around $180 USD in Korea, the 55-300 is around $450. The prices of the three are all within a few dollars of each other, so price isn't a factor in the choice between the 3.. it sounds like the pentax is probably a better lens even though its going to come up short. Maybe I'll start with that this year and and after I've saved up I'll get the 55-300.

I appreciate the suggestions. Unfortunately the Kodak doesn't save any exif data at all, so I can't check the file to find out what it was shot at. I did fire it up to check at full zoom it lets me set it to f/3.7 but the max ISO is only 400.
07-25-2009, 06:40 PM   #12
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QuoteOriginally posted by crossmr Quote
Unfortunately the 55-300 is out of my price range. The 50-200 is around $180 USD in Korea, the 55-300 is around $450. The prices of the three are all within a few dollars of each other, so price isn't a factor in the choice between the 3.. it sounds like the pentax is probably a better lens even though its going to come up short. Maybe I'll start with that this year and and after I've saved up I'll get the 55-300.

I appreciate the suggestions. Unfortunately the Kodak doesn't save any exif data at all, so I can't check the file to find out what it was shot at. I did fire it up to check at full zoom it lets me set it to f/3.7 but the max ISO is only 400.
Since you are on a budget, you can try the Sigma 70-300 DG APO for 210 USD. or the non APO version for 150 USD.

Here is a Sigma vs Tamron 70-300. Although it's on a Canny forum.
http://photography-on-the.net/forum/showthread.php?t=94302
07-25-2009, 07:30 PM   #13
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The price is slightly lower here. I could only find the APO version in the pentax mount its around $176 USD. They have the non apo but only in a nikon mount its around $150USD. It might be a winner. That site doesn't talk about CA. Is the CA significant on the Sigma compared to the Pentax? I couldn't really see much from either lens in any of those pictures.. not too much black against a light background in those pictures. I think I'm definitely going to have to start dragging my tripod to the games.
07-27-2009, 03:07 PM   #14
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I am skeptical when you say your Kodak doesn't include EXIF, because the samples here do. More likely it's an issue with your digital workflow, perhaps you're using a program incapable of reading typical EXIF values or something you're doing is stripping them away.

You should probably be aware that the DA50-200/4-5.6 is considerably smaller and lighter than the typical zoom that extends to 300mm. It is only a little larger than the 18-55 kit lens, and uses the same size filter (52mm). The -300mm zooms generally weigh 2-3x more and are 3-5cm (1 1/4 to 2 inches) longer. So if you're at all sensitive to this, you might want to handle both sorts in a store.
07-27-2009, 03:10 PM   #15
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I'm using exif reader from here:
Exif Reader - English Version

All I've ever done with my photos is use an autofix and resize from Paint shop pro 9. Is it known to destroy exif data? I've grabbed multiple photos and all of them come back claiming no exif data, but I've tested the lens now and know it goes to f/3.7

The size isn't a significant issue for me.
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