Which ƒ1.2 Lens is Better?

[Pentaxor]

Originally Posted by lithos

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.

[Pentaxor]

Originally Posted by Digitalis

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.

[Digitalis]

Originally Posted by Pentaxor

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)

[PentaxForums-User]

Originally Posted by Digitalis

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.

[Pentaxor]

Originally Posted by Digitalis

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.

[PentaxForums-User]

Originally Posted by Digitalis

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.

[Pentaxor]

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?

[Digitalis]

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.

[indytax]

Originally Posted by Digitalis

all this alcoholic smooth blurry rubbish does get boring.

Well put.

10char

[Dan]

Originally Posted by lithos

... 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?

Dan

[Blue]

Another possibility would be to adapt the Nikkor or Rokkor vintage f1.2 lenses.