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03-05-2013, 10:10 AM - 1 Like   #91
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Regarding the FA*24: first of all, I don't think anyone's saying that this lens can't produce good images, or even that it isn't a good lens, just that it doesn't qualify as "legendary glass." I agree with that. It is "historical glass," being one of the first mass produced lenses with an aspherical element, using I believe a resin mold technique that never caught on but which gives the lens a bit of warmth. As far as I can tell, cost-is-no-object Leica didn't release an ASPH lens until 2 years after the FA*24 was released. But I'm not even sure about all of that and such details only matter to collectors, so, onward.

While this post talks about the FA*24 in some detail, I'm really going after what attributes make up a fine lens.

QuoteOriginally posted by Digitalis Quote
You can see the dark centred bokeh circles on specular highlights - which is why the FA*24mm f/2 produces such harsh bokeh. As I recall the Japanese call it "neisen bokeh" - meaning double lined blur. The Ideal bokeh disc has a evenly lit centre which gradually darkens towards the edge.The FA*24mm f/2 it works the other way around slightly darker centre - with bright green/magenta fringed edges.
Yes and no. The nisen bokeh is caused by, as you say, bright outlines of bokeh discs, which is overcorrected spherical aberration. But from everything I've seen, the FA*24 has only moderate overcorrection compared to most Pentax lenses, and is no worse than the "reference class" bokeh of the 50/1.4 lenses. I would be willing to wager that the FA 31 adds more color to its bokeh than the FA*24, too, but I went with a red-dot on my 35mm lens so I can't say that for sure.

What the FA*24 suffers strongly from is a contrast between sagittal and tangential resolution. This exacerbates the bokeh outlines for parts of the disc. Here's an example (shot on film).



Look at the disc bokeh in the trees, upper left corner, where you see the sagittal edges (lines from the center to the edge) are brighter but where the tangential edges (lines equidistant from the center) are much better. Together, they create wedge-shaped ugliness, but this shows that the problem isn't purely circular in nature.

The near focus, light color branches are instructive. Toward the center of the frame, there is no double-lined effect, but this arises with some vengeance with the branch extending to the upper left corner (sagittal) about halfway from dead center. Yet on the right side, nearly the same distance from the center, is a branch with what looks like undercorrected (that is, desirable) spherical aberration, but this one is angled away from, not towards, the corner, which is to say that it is positioned tangentially.

I point this out because a legendary lens should have good spherical correction as well as having sagittal and tangential resolution in parity with each other. For example, the FA 43, despite its colored bokeh fringing and lack of edge resolution, has rather harmonious resolution that leads to pleasing rendering.

QuoteOriginally posted by twitch Quote
Here's an example of what I didn't like, a crop (about 60% of the frame) of a FA*24 shot
Curiously, I think that shot shows what I like about the lens. High contrast yet soft. Lends punch to the overall image without pulling the eye away with unnecessary detail.

We can agree, I think, that the FA*24, though not outright bad, doesn't resolve fine detail well enough to be "legendary." That said, the visual effect of an image--which to me is what makes a successful picture--depends on a first impression made by contrast, which tells the story, and only then uses fine detail to keep the mind interested. As the person who was standing behind the shutter when it released, I don't need to be reminded of the broad strokes in the image, so contrast doesn't seem as important; but for someone viewing the picture for the first time, that's the first thing they see. And the FA*24 gives that in gobs.


So, yes, I think Pentax could design a better 24mm lens, and ought to for any 135-frame camera they release. However, given the options for a much larger f/1.4 lens, much slower f/3.2 lens, slower and optically inferior zoom, or many-fold more expensive alternatives, the FA*24 hits quite a sweet spot in the current lineup. What makes the 24 so desirable is how unique it is: there are lots of very good 35s, 50s, and 85s, but only a slow progression in the area of 24s. While I fully intend to keep my FA*24, I would vote for giving us a similar, more modern lens rather than remaking this 22 year-old design.

03-05-2013, 10:26 AM   #92
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Then you believe the FA*24/2 qualifies as a great Pentax lens - but not in the category of the best of the 20-25 great historical Pentax lenses. If we really are discussing only the legendary lenses then isn't the list liimited to:

FA50/2.8 Macro
A*85/1.4
A*135/1.8
A*200/4 Macro
FA*28~70/2.8
FA*80~200/2.8

Certainly there will be discussion and argument - where is the line between a very good lens, merely a great lens and the very best of the great lenses?

Would those six lenses plus the existing Limiteds, D-FA lenses and perhaps FA35/2 and FA50/1.4 for budget entry be sufficient to launch a FF camera? And could they be reworked and remarketed for an effective price today?
03-05-2013, 10:34 AM   #93
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So since the FA24 has poor traits, this makes the absence of any fast 35mm eq lenses from Pentax even more conspicuous.
03-05-2013, 10:45 AM   #94
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I would say that 24mm is expected at the wide angle of any standard, pro-level zoom, which might moot the issue as far as a 24mm Star lens goes.

There was a K 15/3.5 AL, according to Bojidar Dimitrov, which was apparently too expensive to produce; it certainly is legendary, though more for rarity, but we now have much more affordable techniques to manufacture AL lenses. That, and/or a 20/2.8, would certainly complement the wide end of a standard zoom. I have no idea how the 15/3.5 or 20/2.8 perform, though.

03-05-2013, 05:09 PM   #95
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QuoteOriginally posted by JonPB Quote
There was a K 15/3.5 AL, according to Bojidar Dimitrov, which was apparently too expensive to produce; it certainly is legendary
not because of its image quality. it was sharp enough in the centre - the corners were bothersome. Also the flare tolerance of that lens had was nothing to write home about.

QuoteOriginally posted by JonPB Quote
The nisen bokeh is caused by, as you say, bright outlines of bokeh discs, which is overcorrected spherical aberration. But from everything I've seen, the FA*24 has only moderate overcorrection compared to most Pentax lenses, and is no worse than the "reference class" bokeh of the 50/1.4 lenses. I would be willing to wager that the FA 31 adds more color to its bokeh than the FA*24, too, but I went with a red-dot on my 35mm lens so I can't say that for sure.
Correct, I didn't feel the need to go into toe optical details. the coma from the FA*24mm f/2 certainly doesn't gain it any points, the high contrast nature of the FA*24mm f/2 ASPH is part of its downfall - high contrast and smooth bokeh aren't a harmonious combination. And in my personal experience wide angle lenses benefit the most from being stopped down for images where bokeh is important. typically for good bokeh, a close subject with the lens stopped down perhaps 1-2 stops, and avoiding high contrast backgrounds will make for a pleasing image, but in reality environments are seldom so accommodating.


QuoteOriginally posted by JonPB Quote
I point this out because a legendary lens should have good spherical correction as well as having sagittal and tangential resolution in parity with each other
yes, astigmatism. the FA43mm f/1.9 Limited offers a good contrast between proper astigmatic correction - the lens is so well corrected there was a rumour that suggested the FA43 had an aspherical element in it.

Last edited by Digitalis; 03-13-2013 at 12:46 AM.
03-06-2013, 12:13 AM   #96
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QuoteOriginally posted by JonPB Quote
I would say that 24mm is expected at the wide angle of any standard, pro-level zoom, which might moot the issue as far as a 24mm Star lens goes.

There was a K 15/3.5 AL, according to Bojidar Dimitrov, which was apparently too expensive to produce; it certainly is legendary, though more for rarity, but we now have much more affordable techniques to manufacture AL lenses. That, and/or a 20/2.8, would certainly complement the wide end of a standard zoom. I have no idea how the 15/3.5 or 20/2.8 perform, though.
I see the FA20 2.8 once in a while and that usually lists for about 8-900 Euros. The only other choices are Sigma's fast lenses in the 20-30mm range, which are larger, BUT much, much faster.

IQ is another question.
03-06-2013, 06:52 AM   #97
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QuoteOriginally posted by slip Quote
Why can't / doesn't Pentax manufacture some of the older legendary glass? One of issues stopping some nik/cannon owners is the small present line up (compared to their brands).... So even if they don't make a lot of money on the lenses, it would help grow the name
I believe that it would be good for Pentax to allow for some special orders for the FA* 250-600, FA* 600/4, and possibly the A* 1200; but I dont think a general production run of these lenses will make enough revenue to justify one. any of these new is going to be in excess of USD $10k, and there aren't many current Pentax shooters willing to pony that kind of cash.

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03-06-2013, 07:06 AM   #98
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QuoteOriginally posted by Clinton Quote
I believe that it would be good for Pentax to allow for some special orders for the FA* 250-600, FA* 600/4, and possibly the A* 1200; but I dont think a general production run of these lenses will make enough revenue to justify one
You have a good point there, I would be quite happy if the re-designed the FA*250-600mm f/5.6 with WR and an improved filter drawer it would be quite an attractive wildlife lens.

03-08-2013, 05:26 PM   #99
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QuoteOriginally posted by Digitalis Quote
You have a good point there, I would be quite happy if the re-designed the FA*250-600mm f/5.6 with WR and an improved filter drawer it would be quite an attractive wildlife lens.
Would you pay the $14k for that lens though?

How many here would simply complain about the cost
03-08-2013, 05:36 PM   #100
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QuoteOriginally posted by JonPB Quote
Then Pentax isn't competing for the cheapest camera, but rather the cheapest modern camera system that produces impeccable image quality.
I like that approach.
03-08-2013, 06:16 PM   #101
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QuoteOriginally posted by Clinton Quote
Would you pay the $14k for that lens though? How many here would simply complain about the cost
how many people would complain?: too many probably. Then again the Sigma 200-500mm f/2.8 APO EX DG isn't exactly a big seller. The FA*250-600 f/5.6 is only two stops slower than the sigma and it is considerably easier to handle.
03-10-2013, 05:40 AM   #102
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QuoteOriginally posted by snake Quote
Pentax absolutely needs a fast 24. The absence of a fast 24 in the Pentax lineup is very conspicuous.
Cmpletely agree!!! The 24 is the biggest hole in the Pentax lineup. No APS-C prime between 21 and 35 mm and nothin with wide aperture anywhere until 50/55.
My assumption is that Pentax has no clue when and how a fullframe camera will be presented, so they are not presenting more APS-C glass and can not yet offer fullframe wideangles and other glass at the moment.

Legendary wide angle glass makes no sense on APS-C cameras - too much retrofocus!
A 2.8/300 would have been so much more interesting than the 5.6/560 mm. Same price, more users and happy to go along with a 2x converter. Either Pentax is hiding something or the company will implode. Silly question: Does Pentax own the rights to the FA lenses or is it Tokina/Hoya.
03-12-2013, 10:18 PM   #103
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Still thinking of a wide-angle WR. And not the DA*16-50...

I'd love a 24, but after seeing explanations from Digitalis and others, it seems a little harder to make than I thought.
03-13-2013, 04:56 AM   #104
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QuoteOriginally posted by zapp Quote
Silly question: Does Pentax own the rights to the FA lenses or is it Tokina/Hoya.
Neither Tokina nor Hoya have anything to do with the FA lenses.
03-13-2013, 05:03 AM   #105
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Who makes the parts for FA lenses and who assembles them?

Certainly Pentax has no glass works, which Tokina and Hoya do.
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