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02-10-2011, 04:46 PM   #46
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QuoteOriginally posted by m42man Quote
My contention is that there are plenty of lenses out there - both modern and vintage - which don't provide the resolution the K-5 deserves.
Yes there are plenty of lenses out there that are dogs, that didnt provide adequate resolution for film or 6mp either, but thats just the canine nature of those lenses.

02-11-2011, 03:04 AM   #47
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Most primes do. Of my lenses those gaining the most resolution K-5 are DA14, DFA50, FA*85 and Sigma 180.
02-11-2011, 03:54 AM   #48
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It is safe to say that the FA31mm f/1.8 can easily match the resolution of any current DSLR, I recall one person using the FA31mm f/1.8 limited on a 24Mp D3x and he was more than pleased with the image quality.

The FA77 does remarkably well too as does the FA43 limited. And more surprisingly the SMCP-K 50mm f/1.2 provides impressive resolution at f/2.8 onwards, all the more remarkable considering it was introduced in 1975.
02-11-2011, 04:48 AM   #49
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QuoteOriginally posted by m42man Quote
Did anyone say that old lenses aren't up to the job? I certainly didn't.

In fact, I would go so far as to say that, as far as resolving power is concerned, vintage glass is at least as good as the modern stuff - particularly in the "easier" focal lengths (especially the 50s).

Where the modern glass wins, though, is in the area of autofocus, colour response, contrast, flare resistance and CA/PF.

My contention is that there are plenty of lenses out there - both modern and vintage - which don't provide the resolution the K-5 deserves.
I agree. Pentax has always sold "good glass" at the top, but there have been a few dogs at the bottom end of things. No one is really shooting with those lenses, because of the fact that they look so soft on digital sensors currently in use.

02-11-2011, 04:52 AM   #50
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QuoteOriginally posted by normhead Quote
While shooting a wildflower in my house yesterday I did a couple tests with the old Da18-55 that came with my *ist, and the newer DA 18-55 AL that came with my K-x. The old "not enough for a K20D " DA seriously outperformed the newer AL based on about 10 exposures. I'm willing to bet, the actual build of the lens is more important than any resolution test done in a lab for determining what lens is better.

Pentax can a say they redesigned the lens the lens for digital glass, all they want. I have two lenses 18-55 and the older one works better. And when you think about it, that pretty much means nothing. Maybe the camera didn't select the same focus points. Just because I did the same thing both times doesn't mean the camera did. There's an alternate brain in there that can't be trusted to make the same decision twice.

So, all I'm saying is, I had two lenses, most of the testers only tested on one copy. WHy are their results better than mine?

They probably aren't.

You still have to go out and find a copy of the lens you like.

You can read the reviews but, your experience may vary.

And as I said, I'm still not sure this whole issue isn't a marketing ploy.. to sell expensive new glass to people who don't need it.

Or as someone once said "Advertising will sell you things you don't need to impress people you don't like."
Norm, there aren't really big differences between the kit lens, version I and II. The biggest thing you should notice (if you have a good copy) would be a little improvement in border performance the version II.
02-11-2011, 07:00 AM   #51
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A simple test would be nice!!!

QuoteOriginally posted by m42man Quote
Did anyone say that old lenses aren't up to the job? I certainly didn't..
Someone out there has a 14mp K-5 and an older 6mp camera like a K100D; maybe s/he will do an easy test for us? Just use the same lens on both cameras under controlled conditions! Sounds easy!

First choose a good lens and make sure there is adequate light, identical exposures, ISO 200, for a scene that can't be easily out of focus (maybe a tilted newspaper or grass lawn?), and no PP sharpening.

Test photos I... (approximating an almost perfect lens)

Set the lens at f:8 (almost perfect) and take the same photo with both cameras, compare these photos for a series of enlargements. What do you predict as enlargement increases? I think the photos will look about the same until the enlargement approaches 100% crop for the 6mp camera. The 14mp camera should support almost 50% more enlargement but the increased resolution won't have good contrast.

Test photos II.....(approximating a not-so-good lens)

Same lens as above at f:32, compare photos at the same enlargements for a series of enlargements. The results should be about the same for both cameras because the diffraction limit for the display will be exceeded at the same enlargement (ie. the Airy disk will be larger than the resolution limit for either sensor....similar to a "bad" lens.)

If you thought these were two different lenses and didn't know anything about diffraction limits how would you interpret the above tests?

Here's one interpretation:
--For the "good lens" the 14mp sensor out-resolved (at low contrast) the 6mp sensor for big enlargements.
--For the "bad lens" the 14mp sensor was no better than the 6mp sensor.

Therefore, a 14mp sensor is no better than a 6mp sensor for sufficiently bad lenses*. Perhaps this is a better way to answer the "out-resolve" question?

When the lens is good enough for the 14mp enlargement's resolution to exceed the 6mp's enlargement, contrast enhancement may be required to make practical use of the increased resolution.

Dave

*Is saying a 14mp sensor can "out-resolve some lenses" the same as saying "a 14mp sensor is no better than a 6mp sensor for some lenses"?

Last edited by newarts; 02-11-2011 at 07:41 AM.
02-11-2011, 05:43 PM   #52
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Newarts, I think you are forgetting a crucial factor in any resolution test between cameras - The AA filter, Iger the one on the K5 and K7 is much stronger than the one used in the K100D. The only way to completely level the playing field would be to remove the AA filters.
02-11-2011, 05:51 PM   #53
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QuoteQuote:
*Is saying a 14mp sensor can "out-resolve some lenses" the same as saying "a 14mp sensor is no better than a 6mp sensor for some lenses"?
I'd be really curious to see some shots comparing a lens that is good at 6 mp and bad at 14 mp. I'm sure there are far more lenses that are good on both, or bad on both, than there are that split the difference. But hey, show me. I'm all eyes.

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