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08-26-2010, 08:41 PM   #1
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Lenses...now more confused than ever

It seems the more I try to research and learn about "lenses" the more confused I am getting. I've already checked out the "Pentax lenses explained" section. All I really want to know is about brand names and compatibility. I've seen plenty of reference to other brand names/manufacturers lenses being used with Pentax cameras (eg. Tamron) . Is there a resource that lays it out nice and simple as to what lenses will fit/work with my Pentax (K-x), and which ones will not? This would make shopping for a new lens a lot easier, because right now I don't even know how to narrow it down or where to begin.

Sorry in advance if the answer is elsewhere in these forums, but I have searched and to no avail.

Thanks for any help you can give. I'm really looking forward to learning a lot about my camera and about taking better photos.


08-26-2010, 08:47 PM   #2
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Ah. There is a difference between a lens-maker and a lens *mount.* Pentax-made lenses will all fit Pentax cameras: a company like Tamron makes lenses for several camera brands: so they make lenses with different mounts: they will make a Tamron lens that fits Pentax and a Tamron lens that fits Canon, and a Tamron lens that fits Nikon, etc.

If you want to buy a 'third party' lens, like Sigma or Tamron, you need to know if it's made to fit Pentax, or some other kind of mount. When you buy them, it will usually specify.

It'll be the same lens as made for another brand, almost always, but the mount and related hardware will be different.
08-26-2010, 08:47 PM   #3
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If it is a K mount lens, it will fit your camera. Plain and simple. Brand name does not matter in that case. The only time you need to be careful is with K mount lenses that were made for Some Ricoh cameras (google the Ricoh Pin).

If you look in the Lens Database, odds are pretty good you'll find just about any lens you may be looking at.

Pentax Lens Listings - Pentax Lens Review Database

08-26-2010, 09:39 PM   #4
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I'll give the uuber simple explanation

if it's a Pentax lens or says Pentax anywhere in the item description then it will fit your camera

08-26-2010, 10:14 PM   #5
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QuoteOriginally posted by JeffJS Quote
If it is a K mount lens, it will fit your camera. Plain and simple. Brand name does not matter in that case. The only time you need to be careful is with K mount lenses that were made for Some Ricoh cameras (google the Ricoh Pin).

If you look in the Lens Database, odds are pretty good you'll find just about any lens you may be looking at.

Pentax Lens Listings - Pentax Lens Review Database

The above lens database has every Pentax lens that will fit your camera listed. There's also a link to the third-party section at that top, which, while not exhaustive, will still have almost all lenses you'll typically come across listed.

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08-26-2010, 11:49 PM   #6
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You already received from good advice. Simply your K-x camera has a K-mount. Any Pentax lens will fit. In addition, some 3rd-party lens maufacturers (Tamron, Sigma, Voigtlander, Zeiss) make some lenses with K-mount.

As pointed by Adam, all the lenses listed in the Forum database )(Pentax and 3rd party) will fit your camera.

Another way to look at it is:
- what lens(es) do you have now with your K-x ?

- what type of lens would you like ? what do you shoot ?

The beauty of dSLR cameras is the inter-changeable lenses that allow you to choose the best lens for what you want to shoot. For example, I have myself 3 lenses: (a) a Pentax DA18-250mm that is an all-rounder lens; with that lens, my K-7 is some like a ultra-zoom/long-zoom camera that I can take all day long; (b) a Voigtlander Nokton 58mm f1.4 that is an excellent low light lens; and (c) a Tamron SP 90mm Macro for doing macro.

Each lens does have its advantages and limitations:
- the focal length(s) give you the range; for example the DA18-250mm is like a 14-times zoom
- some lenses are manual focus (MF) and others are auto-focus (AF); my DA18-250mm and Tamron 90mm are both AF; and my Voigtlander 58mm is MF
- the aperture (or f number) is an indication of the lens' ability to work in low light: a low f number means some better low light capability
- there are some prime lens (single focal length) and zoom lens; the prime lenses have usually some excellent image quality (IQ) compared to a zoom len because their design does not need to make a comprise over a range of focal distances; a zoom is more flexible because of its focal length range, but but some good quality zoom lens can be expansive.

All in all you may be best to start simple with the K-x and the 18-55mm kit lens. Once you know better your own preferences, you may consider to invest in some good lenses. (Lenses are expansive but all Pentaxians will tell you that the investment in good "glass" is worth it...

Last edited by hcc; 08-26-2010 at 11:56 PM. Reason: Typos
08-27-2010, 12:48 AM   #7
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The lens review database on this site is the best source for you for pentax mount lens (all types). I have used it extensively before making my purchases, after I have decided the focal length and aperture I want. I use a simple rule - if the number of reviews is 5 or more and the score is 9 or more, buy it. If it is between 8 to 9, do more research before making your decision. Below 8 - buy if you want to experiment and are getting a real good deal.
Final call is yours and yours only.
Try the database - it is a good resource.
08-27-2010, 07:57 AM   #8
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Wow, I wasn't expecting such a large amount of good responses, and all of them very positive. Thank you all for your input and advice. I'm not really sure what I want. I do know I was frustrated after having just returned from the Shanghai Expo, and all my fiance's photos (from her point and shoot Sony Cybershot) were BETTER than mine (at least the indoor ones where the light was low). I later learned this was because the lowest aperture value on my kit lens (the DA L 18-55 mm) is 3.5, and that if I want to shoot indoors under low-light, that I need a faster lens - especially if I also want faster shutter speeds that don't require me to be holding the camera super steady. So, for now I'm probably in the market for a really good prime lense, fast, works well in low-light conditions. But, having said that, I really like the flexibility of being able to zoom in when I want. Wildlife and nature always appeal to me. Apparently I'll be adding to my equipment wish list as I delve further and further into this hobby, but I'm looking forward to it as I'm really enjoying my camera and learning what I can.

08-27-2010, 08:07 AM - 1 Like   #9
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You can also boost the ISO on your camera to be able to use faster shutter speeds. The kit lens is ok, faster zooms are better, prime lenses are the best (in my opinion). As for your lady's p&s giving better results, you might want to browse this thread.

https://www.pentaxforums.com/forums/pentax-dslr-discussion/111350-my-wifes-ni...n-my-k10d.html

08-27-2010, 08:42 AM   #10
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QuoteOriginally posted by slr_neophyte Quote
I was frustrated after having just returned from the Shanghai Expo, and all my fiance's photos (from her point and shoot Sony Cybershot) were BETTER than mine (at least the indoor ones where the light was low). I later learned this was because the lowest aperture value on my kit lens (the DA L 18-55 mm) is 3.5
Actually, I *very* much doubt that's the reason. The maximum aperture on her point and shoot is probably no better - although your 18-55 is only f/3.5 at the 18mm end; you probably shot in a range where it's f/5.6, and hers might be f/4. Still, the high ISO performance of her camera is probably *terrible* compared to your camera's, so whatever IS she was shooting, you should have been able to get the same shutter speed but much better results by shooting one stop higher ISO. Could it be she used flash, and thus wasn't taking low light pictures at all? Posting samples would help. It's entirely possible you simply were not using optimum exposure settings for the situation.

Note, I'm not saying that getting a larger maximum aperture (aka "fast") lens wouldn't be a good idea - just that there is way more to it than that, and your comment above suggests you can probably get better results even with your current lens.

Last edited by Marc Sabatella; 08-27-2010 at 01:46 PM.
08-27-2010, 11:15 AM   #11
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QuoteOriginally posted by Marc Sabatella Quote
I'm not saying that getting a larger maximum aperture (aka "fast") lens wouldn't b a goo idea - just that there is way more to it than that, and your comment above suggests you can probably get better results even with your current lens.
Indeed. The Kx has the best low-light sensor available now. For shooting in iffy light, set the aperture to f/8, and the shutter to 1/80 sec, and let the ISO float up. Use flash when necessary. NOTE: Go to a dollar store. Buy a pack of the thinnest, gauziest white infant's socks you can find. Slip one over the pop-up flash as a diffuser.

And for shooting in REALLY iffy light, with or without flash... that's what fast lenses are for. But fast lenses can be tricky to focus, especially manual-focus (MF) but even autofocus (AF) in low light. And fast ain't cheap... except some manual Fifty primes at f/2 or faster, which can still be found for under US$30. An AF zoom makes it easy to take pictures. A manual prime teaches one to see.

Master the kit lens. Don't worry about buying more lenses until the need becomes overwhelming. For me, that took about three weeks.

Last edited by RioRico; 08-27-2010 at 11:46 AM.
08-27-2010, 06:02 PM   #12
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Hehe, actually when I checked the EXIF info for her shots, her aperture was 2.8, AND she was not shooting with a flash. I also didn't want to use the flash because it seemed whenever I did that, the subject would be too bright and the backgrounds too dark. Sorry I have no samples to post that would compare same scene shots of hers to mine. I do have another setting on my camera that I began playing around with when I got home (SV - sensitivity priority mode), and so far it seems that I am able to get some better photos in low light. It allows me to really boost up the ISO and still have control over EV compensations while it auto selects the aperture and shutter speeds. For now, I definitely will keep trying to master the kit lens. I know that's important for me as a learning photographer before I get into more gear. Thanks again for all the input!
08-27-2010, 07:49 PM   #13
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It is very likely that the Sony lens was at a wide setting if the aperture was 2.8, and there is minimal difference between 2.8 and 3.5 (your lens at a wide setting), so I don't think that's the issue. The low-light capability of the kx sensor (or even my k100 sensor) would outweigh that difference in aperture.

Paul
08-28-2010, 10:50 AM   #14
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Right. The f/2.8 suggests she was at the wide end of the zoom, and if you matched that on your zoom, you'd be at either f/3.5 (half a stop difference) or f/4 (one stop worse). Whatever ISO she was at, if you turn your ISO one stop higher, then you'd be getting the exact same shutter speeds as she was, but you should have *much* (and I mean *MUCH*) less noise in your shots, even at one stop higher ISO. There's nothing she could have done to somehow get better results than optimal, so I'll have to assume that the difference is that you did something to make your results less than optimal. Meaning you didn't have your aperture at maximum, or you didn't have ISO turned up high enough to avoid blur, or it was turned up *so* high that the noise was worse than necessary.
08-28-2010, 10:43 PM   #15
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About shooting in low-light with the K-x:

It's better to have grained images than blurred images (specially at 12 MP). So put the high-ISO quality of the K-x to work, set it to the maximum possible while keeping aperture and shutter as low as you can to get a 0 EV. Play with higher apertures if you need to play with wide-angles and keep everything on focus. Even then, it's guaranteed to get good, focused pics with low-light indoors up to 1600 ISO.

If all fails, cram ISO to the max and take it B&W. You can never go wrong with a grained B&W
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