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View Poll Results: Which 1.2 Lens is Better?
K 1.2 1731.48%
A 1.2 3564.81%
Post 55 1.2 47.41%
Cosina 55 1.2 712.96%
Revuenon 55 1.2 47.41%
Multiple Choice Poll. Voters: 54. You may not vote on this poll

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09-28-2009, 06:57 AM   #16
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QuoteOriginally posted by lithos Quote
Not strictly true, digitalis - the A has nine aperture blades as opposed to the K's eight.
the additional aperture blade has an effect on the IQ. it produces a much better bokeh at the expense of sharpness. from what I observed and experienced, a 6 or 7 bladed normal standard lens have much better sharpness at the widest open possible (1.4,1.7 and f2) as compared to a normal standard lens with an 8 blade, but most especially a 9 blade.

09-28-2009, 07:05 AM   #17
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QuoteOriginally posted by Digitalis Quote
that is true, but I was referring to the optical qualities of the lenses. besides one extra aperture blade doesn't make for a ground breaking difference between the two lenses. At f/2.8 the bokeh of the K50mm f/1.2 is slightly better that the 31mm f/1.8 - in regards to bokeh, most Photographer's would have trouble making a distinction between the two lenses. the FA31mm f/1.8 Limited has a nine bladed aperture.
the 31mm shed off 19mm of significant FOV. this could affect the FOV and OOF bokeh it produces. in a FF, it is a wide angle lens and in an APS-C, it's a normal lens. same goes for a 50mm lens, normal in a FF, telephoto in an APS-C camera.
09-28-2009, 08:24 AM   #18
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QuoteOriginally posted by Pentaxor Quote
the 31mm shed off 19mm of significant FOV. this could affect the FOV and OOF bokeh it produces. in a FF, it is a wide angle lens and in an APS-C, it's a normal lens. same goes for a 50mm lens, normal in a FF, telephoto in an APS-C camera.
In my bokeh "test" I compensated for the differential in FOV. therefore my statement still stands...

"it produces a much better bokeh at the expense of sharpness" - that is weapons grade BS. All the aperture does is defines the appearance of OOF highlights and general OOF areas, it has NO impact whatsoever on resolution.

are you suggesting the FA31mm f/1.8 Limited isn't sharp? all the FA limited lenses feature 9 bladed apertures, and they all perform superbly from wide open to stopped down (the 43 Limited is excused)
09-28-2009, 09:06 AM   #19
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QuoteOriginally posted by Digitalis Quote
that is true, but I was referring to the optical qualities of the lenses. besides one extra aperture blade doesn't make for a ground breaking difference between the two lenses. At f/2.8 the bokeh of the K50mm f/1.2 is slightly better that the 31mm f/1.8 - in regards to bokeh, most Photographer's would have trouble making a distinction between the two lenses. the FA31mm f/1.8 Limited has a nine bladed aperture.
I would agree with both parties... I do prefer 9 blades... it seems sometimes you can tell with the 8 blades, but only when it renders the bokeh jarringly... when the 8 blades do it smooth (all depends on subject and shot), you can't tell at all. I know my FA 77 I think has less than 9 blades and often does jarring bokeh.

But I also hear the K's are built better than the A's? I don't know... I only have an M and am about to buy a K 1.2 probably. I can't find anyone selling an A.

09-28-2009, 09:27 AM   #20
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QuoteOriginally posted by Digitalis Quote
In my bokeh "test" I compensated for the differential in FOV. therefore my statement still stands...

"it produces a much better bokeh at the expense of sharpness" - that is weapons grade BS. All the aperture does is defines the appearance of OOF highlights and general OOF areas, it has NO impact whatsoever on resolution.

are you suggesting the FA31mm f/1.8 Limited isn't sharp? all the FA limited lenses feature 9 bladed apertures, and they all perform superbly from wide open to stopped down (the 43 Limited is excused)
please read my previous statements carefully. I mentioned the word "normal standard lens". none of the FA LTD's that you are saying are pure 50's, so that in a way doesn't qualify your argument as valid. and I didn't mention the FA31 isn't sharp. btw, when I said better bokeh, it is the one that you had described that has a different OOF appearance. for me, that bokeh appearance is better and that's no BS statement.

btw, you cannot compensate lenses with different focal lengths by adjusting the focus distance or range. even if you had successfully compensated for the image size/FOV and DOF of your main subject in the foreground inorder to produce the length size, the size or FOV range of your background image will be different (either wide or close). I tell you that this is no BS statement either because I already tested it with lenses of different fl. the test of course involves close-up shots. you can check or test your foreground and background relationship as well if you want, just to make sure that this ain't BS.

btw, I think there was a thread here before regarding that difference. you might as well want to check that out as well and see the difference.

Last edited by Pentaxor; 09-28-2009 at 10:43 AM.
09-28-2009, 09:35 AM   #21
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QuoteOriginally posted by Digitalis Quote
all the FA limited lenses feature 9 bladed apertures
I have an FA 77... is it 8 or 9 blades? Because I always get jarring bokeh on it. But yes, they are all sharp from wide open.
09-28-2009, 09:56 AM   #22
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digitalis, you might have misunderstood my statement. so I might as well explain it to you a bit more. I didn't say the 1.2 isn't sharp either. but rather the level of sharpness. as I have mentioned before in other threads, my 1.2 or in general the 1.2's are softer. more of a soft-sharp effect, I hope you get what I mean by that. and this is a fact. if you would compare a 50 1.2 or even a 1.4 to a 50 1.7, you will see what I mean. can I produce a sharp image with a 1.2? YES. does it have the same level of sharpness of the 1.7? NO ! btw, the 1.7 only has 6 blades. it is sharper, but bokeh is not excellent.

wait a sec, we are talking about 50 lenses here, how in the world does this concern the FA LTD's which aren't 50s?

Last edited by Pentaxor; 09-28-2009 at 11:00 AM.
09-28-2009, 05:29 PM   #23
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I brought the FA limiteds because they are often the benchmark for smooth bokeh and High resolution (especially the FA77 which was Engineered for optimal bokeh performance). Yes I do understand what you're saying. However, I don't think the number of aperture blades has anything to do with a lens's performance wide open. I have an A 50mm f/1.7 (it's more like a 54mm lens not the standard Zeiss, Leica, Pentax, "standard" 51.6mm) and even when it is stopped down in comparison to the K 50mm f/1.2 the f/1.2 lens is superior in terms of IQ especially in the corners. And the bokeh of the 50mm f/1.7 has a charm of it's own, all this alcoholic smooth blurry rubbish does get boring.

09-30-2009, 01:17 PM   #24
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QuoteOriginally posted by Digitalis Quote
all this alcoholic smooth blurry rubbish does get boring.
Well put.

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09-30-2009, 01:47 PM   #25
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aperture blades and "star" patterns

QuoteOriginally posted by lithos Quote
... the A has nine aperture blades as opposed to the K's eight.
In my experience, the main difference between 8 blades and 9 blades is the difference in "star" patterns that appear when shooting a night scene with bright lights. When the lens is stopped down, the 8-blade lens will yield 8 spikes, whereas the 9-blade lens will yield 18 spikes. While this is clearly a matter of taste, I much prefer 8 spikes to 18. 18 spikes is too many. I have been thinking of purchasing a 50/1.2. Based on this consideration alone, I would prefer the K version.

How many aperture blades are in the Cosina?

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09-30-2009, 02:06 PM   #26
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Another possibility would be to adapt the Nikkor or Rokkor vintage f1.2 lenses.
01-27-2010, 02:17 PM   #27
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QuoteOriginally posted by Dan Quote

How many aperture blades are in the Cosina?

Dan
Looks like 8 on mine. I understand some have 9.
01-28-2010, 03:33 AM   #28
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QuoteOriginally posted by Pentaxor Quote
the additional aperture blade has an effect on the IQ. it produces a much better bokeh at the expense of sharpness. from what I observed and experienced, a 6 or 7 bladed normal standard lens have much better sharpness at the widest open possible (1.4,1.7 and f2) as compared to a normal standard lens with an 8 blade, but most especially a 9 blade.

I'm interested, how is this supposed to work? Now stopped down there could theoretically be a difference in sharpness caused by number of aperture blades, though I doubt it (but if you have some test or physics that can back it up I'm interested).

But in the example of the K50/1.2 and the A50/1.2 shot wide open they would have to be identical as the aperture blades are fully retracted, optically it is like shooting without aperture blades.


Came to think of one further question. Does this also apply to other focal lengths than 50mm's? That is that around 6-7 aperture blades produce sharper pics. than an 8-9 aperture blade lens?

Last edited by Jimfear; 01-28-2010 at 03:46 AM. Reason: further question...
01-28-2010, 05:48 AM   #29
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QuoteOriginally posted by Jimfear Quote
I'm interested, how is this supposed to work? Now stopped down there could theoretically be a difference in sharpness caused by number of aperture blades, though I doubt it (but if you have some test or physics that can back it up I'm interested).

But in the example of the K50/1.2 and the A50/1.2 shot wide open they would have to be identical as the aperture blades are fully retracted, optically it is like shooting without aperture blades.


Came to think of one further question. Does this also apply to other focal lengths than 50mm's? That is that around 6-7 aperture blades produce sharper pics. than an 8-9 aperture blade lens?
I did some further contemplation and observation regarding that observation before. from what I had observed further, I don't think that it is not only a matter of number of aperture blades, but also optic design and coating as well. with these factors affect light transmission and rendering altogether.

I understand that when lenses are wide open, is the general notion that it is shooting without aperture blades, or is it? it does look like it if we are going to look at it using our naked eye. my feeling is, that inspite of the fact that both lenses are 1.2 and could had been similar in optical design, I do somehow doubt it due to the number of blades and quite shorter and lighter design of the other lens. such number of aperture blades would had been needed for that particular optical design in the area of light transmission and part necessity. I don't believe it was only left there just for bling or spinal tap connotation. I do think that at stop down, this added extra would have some different subjective rendering as well (probably around the sharpness and bokeh level).
it's too bad that I don't have the K version to make the comparison and I'm quite curious to find something unique or different in the images (similar subject) produced by the 2 lenses as well.

I do somehow hope I could find someone who has a "K" copy just for comparison and testing purposes. if not, maybe buy 1 for 50-100 bucks (200 I still might consider).

p.s. I might do some more extensive testing between 4 types of 50mm lenses under controlled setting.

Last edited by Pentaxor; 01-28-2010 at 06:00 AM.
01-28-2010, 09:14 AM   #30
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QuoteQuote:
But in the example of the K50/1.2 and the A50/1.2 shot wide open they would have to be identical as the aperture blades are fully retracted, optically it is like shooting without aperture blades.
That is exactly what I was thinking.

The A and k version of the 50mm f1.2 has the same optic design and coatings. The only difference in the coatings would be the batch number of the coatings as well as the glass blanks.

I can't say about Cosina, but the Tomioka 55mm f1.2 variations including the Yashinon and Mamiya variants may have some differences in optical placement and/or coatings.
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