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10-27-2007, 02:43 PM   #1
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Are the K85mm/1.8 and FA77/1.8Ltd really that great?

I stumbled upon a resolution test, comparing for example the FA50mm/1.4 with the "legendary" K1.8 85mm. Much to my surprise, the former defeats the latter in this test.

And what struck me even more: the 77mm/F1.8 limited is hardly any better than the 85! Do I misinterpret the data? Did the tester mistake what he saw?



Or does this proove that the legendary sharpness of these two lenses is overrated?
Only too bad that the (F)A*85mm/1.4 was not tested!

Here is the link to what I'm talking about: Measured Resolution Numbers

10-27-2007, 03:18 PM   #2
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There is more to lens quality than mere resolution, and thare are various methods for meassuring lens performance. Most widely accepted is MTF, which some consider a more relevant indicator of lens quality than line pairs per mm.

Understanding resolution and MTF

Then there are distortion, various other optical flaws and subjective factors like 'bokeh' (how the out of focus areas are rendered) and color rendition.

All in all, any lens represents a compromise on all these factors. Which lens is best for you is for you to decide.

Last edited by Ole; 10-27-2007 at 03:36 PM.
10-27-2007, 03:56 PM   #3
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Interesting tests, but not scientifically valid. If we need to pixel peep instead of looking at real world results, pure resolving power of the lens is only one factor. If that is what we are looking at, so be it - BUT the tests should be scientifically valid. To be valid, they must be repeatable. Notice the disparity between the two testers. What this means is simply they are not using standardization in their procedures, and one cannot extrapolate any more validity to their findings beyond which the individual tester found wit their lens sample on that day. I cannot thus see any possible "grade" one can give lenses in an unscientific test such as this. (To their credit, they don't promise these tests are scientific or repeatable anyway.)

Just for fun, I ran my own informal resolution comparison test at f11 in RAW (and used an unscientific and unrepeatable procedure as well.) My subjective rankings were:
1st - 50-135mm @ 75mm.
2nd (tie) - 50-135mm @ 50mm.
2nd (tie) - 77mm.
4th - 43mm.

All these lenses are considered consistently high in resolution, perceived "sharpness," pleasing bokeh and color reproduction.

So pure resolution numbers actually don't mean much at this high level of performance; slight differences in test procedures and lens-to-lens variation is enough to skew the results slightly one way or another. I would only use the above test numbers to see gross differences in lenses, not slight differences that are unnoticeable in real world results.

And, yes, I knew the 50-135mm was an amazing lens, but even I was surprised to see a zoom could hold its own with one of the sharpest primes ever made by anyone, at least as far as resolution goes.
10-27-2007, 06:34 PM   #4
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QuoteOriginally posted by Syb Quote
I stumbled upon a resolution test, comparing for example the FA50mm/1.4 with the "legendary" K1.8 85mm.
These test results are not very usable: we don't know at which f-stop the resolution figures were measured. Some lenses are better well stopped down, others are better near wide open. You cannot make any comparison by looking at the figures measured at only one f-stop.

Cheers!

10-27-2007, 06:35 PM   #5
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I haven't used the K85/1.8, so I can't directly comment on it. But I've handled the other fast 85's and the 77. I can say that I've produced stunning images with the 77 that made my jaw hit the floor. But the A*85 and FA*85 are even a notch better than the 77.

The 77 puts together a beautiful blend of color, contrast, sharpness, resolving power, bokeh. The *85 lenses do the same, only better. This is my subjective evaluation from normal use by the way, not from pixel peeping (I don't pixel peep).

A* and FA* glass are very nice.
10-27-2007, 07:39 PM   #6
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Look here: http://www.takinami.com/yoshihiko/photo/lens_test/acknowledgement.html

This gives an explanation of Yoshihiko Takinami testing methods and more complete test results, by aperture setting. While they perhaps are not the most scientific testing method, he does try to control the situation. I believe, while not comparable to others findings, they are quite accurate when compared with other tests he has personally done.

EDIT: And yes, the 77 and 85 really are that great!

Last edited by kbrabble; 10-28-2007 at 09:28 AM.
10-29-2007, 04:20 PM   #7
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Anyone made a comparison shootout between 85 and 77?

Thanks
Syb
10-30-2007, 07:31 AM   #8
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I think I've read user accounts that the 85 1.8 isn't as good as it's * cousins. So it's probably not the "legendary" lens being compared to.

Just a thought.

10-30-2007, 07:40 AM   #9
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QuoteOriginally posted by Syb Quote
Anyone made a comparison shootout between 85 and 77?
Look here:
Auflösung von Pentax-Objektiven (77mm - 85mm) Resolution of Pentax lenses
Pentax 77mm- und 85mm-Objektive: Test-Portrait-Detail
Objektivtest 85er: Portrait : 85mm lens test

They are all very good lenses!
Interesting how good the M85 is. The price (and lens elements) difference shows how much is needed to get a very slight improvement.
10-30-2007, 06:26 PM   #10
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Thanks for those links. I just bought the SMC Takumar 85mm f1.8 and really couldnt find any good examples on the net. After shooting with it for a couple of days, I would say it lives up to its legend as one of Pentax's best. Its sharp at 1.8 and at least appears to be sharper at 2.0 than my DA 70mm at 2.4.

Last edited by kbrabble; 10-30-2007 at 06:36 PM.
10-31-2007, 02:42 AM   #11
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Interesting test of the resolution of Pentax lenses. I see the 77mm achieved an outstanding 95 (at f8.) To me, these tests are more scientific because they are reproducible and repeatable.

Plus, they also jive with my real-world results that suggest that the 77mm is one of the sharpest lenses ever made by anyone. Just for fun, I reran my unscientific informal resolution test at f8, and I found the 77mm edged slightly past the 50-135mm at 75mm, and was well ahead of my 28-105mm, which exactly matches the results of the Arnold Stark tests above.

I don't have an 85mm, but I am delighted to see that the 50-135mm can come close to the 77mm in my informal tests. The more scientific tests also reinforce what I have always said about the 77mm.

However, as many of the much more talented persons than I have already stated, there is far more to a lens than just the raw resolution numbers. This is why I try to draw some analogies when comparing my lenses back-to-back: I have said that the feeling one gets from the 43mm and 77mm lens is like your first really really romantic kiss. Contrast that with the very capable 40mm and 70mm; I liken them more to kissing your sister.

I am at a loss for similes for the 50-135mm though. Perhaps your first really hard passionate kiss while hurriedly pressed up against the wall of a bathroom somewhere?

(Dang, I think I REALLY need to get out more!)
11-27-2007, 08:35 AM   #12
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I had the legendary A* 85 f1.4 and this was one of the best i ever use.. I sold this and my old pentax system a long time ago to buy a Cotax G2 with some lenses but I never find a lens like this (better than Zeiss in my opinion).. over the top!
02-02-2008, 05:14 PM   #13
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I have bought a 77mm ltd a short while after firstly posting this thread. I am very happy with it, it produces nice sharp portraits and great background blur.

Pity I do not have the 85 to make a decent comparison
02-03-2008, 05:27 AM   #14
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QuoteOriginally posted by Bonfa Quote
I had the legendary A* 85 f1.4 and this was one of the best i ever use.. I sold this and my old pentax system a long time ago to buy a Cotax G2 with some lenses but I never find a lens like this (better than Zeiss in my opinion).. over the top!
Same opinion here:
A* 1.4/85 is a superb lens.
I had the K 1.8/85 too - but the A* has something that makes it different!
It's not only a question of resolution but colour and bokeh too.
Sadly I sold the A*.
The K 1.8 was sold because the Tamron 2.8/90 macro is at least same level but macro lens additionally.
- and cheaper....

:-) Paul
02-03-2008, 10:26 AM   #15
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Here's why I like my FA 77 limited. Made today on my first outing with this lens.













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