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Old May 14, 2007, 2:52 PM   #1
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I ran across this lens at a local store for $99, pretty good shape as far as I could tell, zoom felt a little loose to me. I was just wondering if anyone has any experience with this lens they would like to share.

Here is what it looks like


My other choices would be the DA 50-200, Sigma 70-300 or Tamron 70-300
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Old May 14, 2007, 9:03 PM   #2
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Hi fisheye,

The Pentax 100-300s aren't known for their sharpness wide open, however, stopped down, they are as good as anything else. The problem with that is that it may limit you too much to use it only in brighter light. $99 is about what it's worth, but you could probably do better in price if you looked around.

Personally, I'd go with one of the new lenses you mentioned, with the Pentax for size and weight, and the Tam or Sigma for the reach, if you feel you need it. They are pretty much too close to call from what I've seen from users.

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Old May 15, 2007, 12:01 AM   #3
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If you're just looking for a telephoto lens for general use, the DA 50-200 is probably the safest bet. It's universally regarded as a high quality lens for the money.

The only problem is that it doesn't have the reach of the other two, or the speed at 200mm. However, I've found that a DA lens will expose a half stop or more brigther than a non-DA lens at the same f-stop. I'm not sure if this is always true, but I tested my 18-55 kit lens against an SMC A 50mm, both at f/8 and the kit lens was 50-75% brighter. So, the lens may actually perform more like f/4.8 at 200mm, and with a 1.4x TC, that would be f/6.7 equivalent at 280mm, not much darker than the 70-300 lenses. I just don't know how it's performance with a TC stacks up against the other lenses without.

I've done a moderate amount of research on the other lenses, and have yet to make any kind of decision about what I want for myself. Here's what I've gathered, though there's a lot I don't really know for certain (a lot of this is based on people's opinions, which vary a bit).

There is a cheap Sigma 70-300 lens out there for about $130 which is generally regarded as an OK lens with decent sharpness (some say sharper than the APO), but quite soft beyond 200mm and with noticeable CA (chromatic aberration, AKA fringing).

The Sigma 70-300 APO lens is supposed to be a decent performer at about $220 with much reduced CA, but still soft beyond 200mm.

Then there's the Tamron 70-300 DI lens for around $180. From what I can tell this is a rather sharp lens, probably sharper than the APO at 300mm, but is very prone to CA at longer focal lengths. I've tested this one personally, but only very briefly. It did seem sharp at the time.

There's one more lens most people would probably discount, and that's the Quantaray 70-300 available for $150. I tested this one out for a while at a local Ritz camera shop. The dealer there said these lenses were rebranded Tamron DI lenses sold for less, and performance-wise it did appear that that may be the case.

At 300mm I got suprisingly sharp results shooting signage across the hall in the mall. At f/8 I'd say it looked almost tack sharp, but wide open it wasn't too far off. It also exhibited obvious CA when I shot the skylight. The fringing was actually bright green when shooting white ceiling against blue sky, and rather thick.

Unfortunately, I did the testing with their own camera and card and don't have the results to share with you. Perhaps I'll go back with my own card and retest the camera if start to seriously consider purchasing the lens.
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Old May 15, 2007, 3:08 PM   #4
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Thanks guys for the input! For some reason I am leaning towards the Sigma non APO as I have some money in my Paypal account that I want to drain (burning a hole in my pocket :G) I have the kit lens and I think together they would cover my needs. It has the 1:2 Macro which is nice, and I have a Phoenix 1:1 macro is needed. My biggest hang up is the weight I guess, I know its a longer lens but it's twice as heavy as the pentax.
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Old May 19, 2007, 1:29 AM   #5
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And hey for the $$$$ difference the the non APO 70-300mm is not that much worse if you dont put it into stretching circumstances.

Personally I have a Sigms non APO (DG) 70-300mm and its great especially for the $80+ less dollar cost... if you don't push it optically.

Just don't even CONSIDER zthe 28-300mm's those are REAL compromises.... the 70-300mm are quite nice. (And if Tam.... considerable difference between 75-300 and the 70-300mm)

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