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08-24-2012, 01:29 PM   #1
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Build vs optical quality

I might be nuts, but I hope Pentax comes out with some fast but light/plastic lenses. I can't afford a * but would like to be as close to it as I can without mortgaging the house. After all these years and the advances in plastics and other materials I can't understand why that don't do more R&D.Hope that the heavy metal of past isn't the only thing that holds good glass in the future.Is it the consumer's perception that good glass has to be in a metal casing? If, for instance they come out with a carbon fibre (just and example out of my hat) would people think it is cheap?

anyone else yearn for fast, high quality but affordable auto focus glass that they don't need to take to the grave with them?

thanks

all opinions welcomes of course!

thanks

randy

08-24-2012, 02:02 PM   #2
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But isn't this what Pentax is doing by releasing the da 35 f/2.4 and da 50 f/1.8?
08-24-2012, 02:08 PM   #3
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QuoteOriginally posted by seventysixersfan Quote
But isn't this what Pentax is doing by releasing the da 35 f/2.4 and da 50 f/1.8?
do you think this could be a trend or just a one off thing? are they really comparable to their closest * lenses (optically of course)?




thanks
08-24-2012, 02:25 PM   #4
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Not sure how they compare to * lenses because I don't have any. However, the da 35 f/2.4 has been very favorably compared to the FA 35 (similar optical formula) as well as the da 40 limited, in terms of image quality. It's build quality leaves something to be desired but for its low cost, it is an excellent value. The da 50 f/1.8 is new and I am not sure how it stacks up to fa 50 or f 50. Probably no comparison to da* 55 f/1.4 but then again that lens is almost 3x the price...

08-24-2012, 02:26 PM   #5
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I bet this is a trend. Hope they make a cheap version of fa 28 or a 24mm lens
08-24-2012, 02:27 PM   #6
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The DA* lenses are plastic you know?
It's only the limited lenses and the DFA100 wr that are from metal these days.
08-24-2012, 02:40 PM   #7
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I think it's the glass that is heavy, not the case. I have no problem with plastic - it lasts for years - possibly forever. I'm not fond of plastic optical parts, though.

People admire or complain about "build quality" though I doubt many people can define it. Also, I bet that metal-bodied lenses would be rated higher than an identical plastic-bodied lens even if they had the identical tolerances and IQ.
08-24-2012, 02:48 PM   #8
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QuoteOriginally posted by slip Quote
do you think this could be a trend or just a one off thing? are they really comparable to their closest * lenses (optically of course)?
No, they're not really comparable to * (or Ltd) lenses, but they're still pretty good and are worth the $ (I had FA35/2 before FA31 and F50/1.4 before FA43).

I think they also need a 20 or 24mm version, plus maybe an 85.

08-24-2012, 03:45 PM   #9
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I have to wonder just how much controversy over "plastics" vs. metal build quality should have been attributed to conditions other than the material its self.

There are a LOT of precision tools that are today made of non-traditional metal materials that are readily accepted by knowledgeable users and there are undoubtedly many benefits from that change including some economics of manufacturing and corrosion resistance.

Consider for one thing that the change over occurred while transitioning to auto-focus bodies with different design goals and requirements. If nothing else, the 270-degree arc for focusing posed a tremendous problem for AF motors and speed. This difference should not be attributed to "plastics".

A few other considerations:

"Plastics" require a different manufacturing tolerance than milled metal helical threads and lubricants and have different thermal expansion characteristics.

The weight of advanced optical glass formulas and 'fast' lenses needed an off-set in weight.

AF lens bodies simply had to become larger, and therefor heavier, if not compensated for by lighter construction.

It's a trade-off and one we don't have a useful comparison to debate.

H2
08-25-2012, 05:26 AM   #10
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I think we're just now entering a time where plastics will come to be viewed on a par with metal lenses. From what I understand, the problem in the past had to do with longevity. Part of the formula for sharpness has to do with being able to hold the lens elements in alignment. In the past, plastic lenses would start out great, but would lose sharpness over time due to the alignment getting off-track. I think that as plastic continues to narrow the reliability gap between itself and metals, we'll see more and more great, inexpensive lenses coming out.
08-25-2012, 09:44 AM - 1 Like   #11
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I wonder what the roadmap's "DA high magnification zoom" will be. The previous DA 18-250 was a Tamron joint venture and lacked quick-shift. They could do a plastic mount and no quick shift on the new one too.

That is the most likely next cheap lens. I doubt the long prime will be cheap. Then you run into the old Pentax problem, not enough resources or market share to plug all the holes in the lens lineup right now. I agree that a cheap ~24 and a cheap ~85 would be popular and useful. But I don't expect them soon.
08-25-2012, 10:40 AM   #12
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There is plastic on the DA* lenses, someone mentioned it above.

I think that Pentax does a pretty good job of offering some good glass at affordable prices. The new 35 2.4 and 50 1.8 are definitely better than the kit lenses and offer a good IQ without going into the DA* and FA Limited price range. I think that Pentax has always tried to have an eye towards affordability. I think they could expand these cheaper prime lenses to something super wide and portrait and that would make a lot of people happy. A 4 lens middle-of-the-road line-up would really speak to the price conscious Pentax user.

I also know (because I own a lot of it) that the DA* and the FA Limiteds are also a good value. As expensive as they are, many of them still cost less than a Canon L Series lens and offer the same IQ (if not better - I find Pentax's color rendering to be superior to Canon, IMHO). It is that value that has kept me in Pentax as a working pro despite the fact that I am missing the coveted FF. I don't love the thought of how much money is invested in my current camera gear, but I do know that if I was shooting Canikon there would be a lot less in my bag for the same investment.
08-25-2012, 07:49 PM   #13
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QuoteOriginally posted by slip Quote
Is it the consumer's perception that good glass has to be in a metal casing?
I suspect many consumers don't care. That's why we continue to get plastic lenses, particularly with kit zooms and lenses like the DA 35/2.4. Perhaps it's a wise cost cutting measure with primes, but not so sure it's a great idea for the better sort of zooms. I have the FA 24-90, an unusual lens in that it features prosumer optics in predominantly plastic body (it does have a metal mount). The cheaper plastic build means the lens in more susceptible to zoom creep and AF problems, and of course possible durability issues.

QuoteOriginally posted by Anvh Quote
The DA* lenses are plastic you know?
Which DA* lenses are plastic? I only have the DA* 300 which, other than the hood and the caps, has very little plastic.

QuoteOriginally posted by Allison Quote
I do know that if I was shooting Canikon there would be a lot less in my bag for the same investment.
I suspect if I were shooting Canikon I would have half what I have now, and the primes wouldn't be as good.
08-26-2012, 01:22 AM   #14
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I've the DA*16-50 and DA*50-135 and just felt them again, they are certainly plastic, very high quality plastic though just like the K10D and K20D are.
I've used the DA*60-250, DA*200, DA*300 and DA*55 and i cant remember they felt differently.

If you want to test it simply put the lens in the refrigerator for 5 minutes wanna bet it doesn't feel cold to the touch.
08-26-2012, 02:03 AM   #15
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QuoteOriginally posted by DSims Quote
I think they also need a 20 or 24mm version, plus maybe an 85
I was just going to suggest the same thing, great idea I think

Also the DA*55 is indeed plastic although a high quality polycarbonate (I think) body. I have not had the opportunity to try the other DA* lenses but I would imagine that they are of the same build type as similarly classed Pentax lenses usually share build specs.

Edit: I would trust Anvh's above description and suggestion

Last edited by Zaphodmonster; 08-26-2012 at 02:05 AM. Reason: update of description
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