[PiotrKrochmal]

Hi Everyone,
So my question is to buy or not to buy some 50 f/1.2 lens
According to DxOMark - F-stop blues
theoretically it could be no difference between f/1.2 and f/1.4 lenses.
So please help if you are those who have both lenses please make 2 photos in manual mode and check what is real benefit of 1.2 theoretically its 1/5 EV.
But 50 f/1.2 cost 5xtimes more than 50 f/1.4
So how its work on K5
Best Regards
Piotr

[.a.t.]

There's a good comparison here:
the Normal Lens Shootout Photo Gallery by Sean Carpenter at pbase.com

Also this (55 1.4 vs 50 1.2):
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/129920-da-55mm...0mm-1-2-a.html

[RioRico]

I have the K50/1.2 (US$250), the Super-Takumar (US$55) and FA 50/1.4 (US$200 when I bought it), a planar Yashica ML 50/1.4 (US$10), and a Tomioka 55/1.4 (US$2.25). The K50/1.2 shows much thinner DOF than any of the others and also has beautiful bokeh, besides being slightly sharper when stopped-down. Is the K50/1.2 really 111x better than the bargain Tomioka 55/1.4? Probably not. But f/1.2 lenses DO provide different results than 'slower' lenses.

[Rondec]

The 50mm f1.2 lenses have the best bokeh wide open of all of the 50mm lenses made by Pentax. Just really have the ability to render even fairly busy backgrounds in very smooth ways. Of course, they have an additional 1/2 stop of light capability. They are also manual focus only (although it sounds as though you are comparing them to the manual focus f1.4 lenses). As to whether or no the differences are worth the difference in cost is something that only you can answer.

[stevebrot]

There is a huge difference in DOF that is not well appreciated until you mount an f/1.2 lens on your camera. I would love to have one, but am too cheap.


Steve

[grhazelton]

I have the K50/1.2 (US$250), the Super-Takumar (US$55) and FA 50/1.4 (US$200 when I bought it), a planar Yashica ML 50/1.4 (US$10), and a Tomioka 55/1.4 (US$2.25). The K50/1.2 shows much thinner DOF than any of the others and also has beautiful bokeh, besides being slightly sharper when stopped-down. Is the K50/1.2 really 111x better than the bargain Tomioka 55/1.4? Probably not. But f/1.2 lenses DO provide different results than 'slower' lenses.

RioRico has covered it nicely. I also have both the 1.2, the A1.4, and a 1.7, all Pentax. The relative costs of the three reflect the law of diminishing returns, there is no question that the 1.2 is objectively not worth five or more times the others. But all is not objective in photography. I bought it with my LX because momentarily I could "afford" it. It is a fine walk around lens, except for the weight, able to render a lovely background, and of course is unbeatable in low light. On the LX on a tripod you can photograph things you can barely see.

On my K10d it makes a wonderful portrait lens, 75mm equivalent in 35mm. But focussing without the KatzEye I found difficult since the DOF is so small and it seemed that the AF indicator didn't render the focus where I wanted it. The dread back/front focus error? With the KatzEye all is fine; of course I'm most used to manual focus with microprism or split image anyway.

I like it best on my MX, a tiny package with a huge lens. Leap tall buildings at a single bound, etc.

[pinholecam]

I used to be an 'atheist' on this.
Logic rules. How can a 0.2 stop make any difference?


But,
Now I am a believer



there is also here:
https://www.pentaxforums.com/forums/lens-clubs/74819-post-your-1-2-photos-1-2-only.html


At the very least, the lens inspires me to shoot more with it.

[Just1MoreDave]

... check what is real benefit of 1.2 theoretically its 1/5 EV...

... How can a 0.2 stop make any difference?...

It's misleading or wrong to subtract 1.2 from 1.4 and turn the decimal into a fraction of a stop. The scale doesn't work that way. The difference between f1.2 and f1.4 (which I'm writing incorrectly but won't change ) is a half-stop, 0.5 Ev.

The DxO Mark article linked to in the first post implies that for other brands, there may be some trickery involved in how the camera acts with an f1.2 lens, but that trickery isn't possible with a K50/1.2 or a Cosina 55/1.2. The camera has no idea that those lenses are mounted. I guess it could be programmed to note that the user has set SR to 50mm and then notice if an f1.2 lens is mounted, then do some sneaky adjustment, but that's too much trouble for Pentax to worry about, I think. Anyway, it would be mildly interesting to see if there's a half-stop of brightness difference between f1.2 and f1.4. It would not surprise me if there was vignetting - tests from when the lenses were new show that.

[RioRico]

It's misleading or wrong to subtract 1.2 from 1.4 and turn the decimal into a fraction of a stop. The scale doesn't work that way. The difference between f1.2 and f1.4 (which I'm writing incorrectly but won't change ) is a half-stop, 0.5 Ev.

Allow me to bloviate on this a little.

The f/stop scale for full-stops goes like this:

f/1.0
f/1.4
f/2.0
f/2.8
f/4.0
f/5.6
f/8.0
f/11
f/16
f/22 etc

The half-stops (at the fast end) go like this:

f/1.0
f/1.2
f/1.4
f/1.7
f/2.0
f/2.4
f/2.8
f/3.4
f/4.0
f/4.8
f/5.6 etc

The difference between f/1.2 and f/1.4 is the same as between f/4.0 and f/4.8, which is 0.5 EV aka 1/2-stop. Those jumps look weird because they're based on the square root of 2, about 1.4. Each full stop lets in half or twice as much light through a roughly circular iris. Doubling the area of the iris circle doesn't double its diameter; it increases by... the square root of 2!

Note: It's common for lensmakers to fudge their ratios a little. We see lenses marked f/1.7 or f/1.8, or f/1.9 or f/2.0, and we see many at f/3.5, which is 2/3 stops from f/2.8. I read that the famous FA50/1.4 is actually more like 52/1.5. Somehow, marking a lens at f/1.9 instead of f/2, or f/3.9 instead of f/4, makes it seem faster. Just like 99 cents is way less than a buck, eh?

Some makers used different numbers; I have an old USA-made Argus Cintar 50/3.5 that's marked f/3.5--4.5--6.3--9--12.7--18 (and I'll be selling it soon, if anyone want a collector's item). But with our dSLRs we can step through the square-root-of-2 scale in 1/2-stop or 1/3-stop intervals, and thus pick almost any aperture we wish. Such power! Hold me back!

[steve1307]

I used to be an 'atheist' on this.
Logic rules. How can a 0.2 stop make any difference?


But,
Now I am a believer

I believe.
.
.

f1.4?

What is this f1.4 that some people speak of?

There is no f1.4

[axl]

It all depends.
There is definitely is a difference between f1.2 and f1.4. 1.2 is pretty much unbeatable. In this respect. Full stop, period!

But in Tv the difference isn't so big, especially when I was comparing K series 50/1.2 with DA*55/1.4.

[Ben_Edict]

Hi Everyone,
So my question is to buy or not to buy some 50 f/1.2 lens
According to DxOMark - F-stop blues
theoretically it could be no difference between f/1.2 and f/1.4 lenses.
So please help if you are those who have both lenses please make 2 photos in manual mode and check what is real benefit of 1.2 theoretically its 1/5 EV.
But 50 f/1.2 cost 5xtimes more than 50 f/1.4
So how its work on K5
Best Regards
Piotr

Hi Pjotr

I have read through the short Dxo article and cannot make too much sense of it. Certainly vignetting gets more pronounced with wider apertures and certainly the number of light rays, coming onto the sensor at an oblique angle also increases, which is the very reason of the vignetting. But basically this does not alleviate the difference between a 50/1.2 and a 50/1.4 - which is half an f-stop or EV (not only 1/5th as you indicate).

It may well be, that a camera, which meters averaged brightness across the whole fiel of view would compensate for the vignetting, wheras a reading taken just off the center of the viewfinder would be immune to the vignetting effect.

I have been using the Pentax M/A/FA 50/1.4 and the A 50/1.2 and there is a noticeable (1/2 EV) difference between these, at least on the cameras I use(d) (istDS, K10, K20, K-r). I am also not sure, whether some camera makers really increase ISO automatically to feign a speed advantage of the supposedly faster lens. I am not under the impression, that Pentax does that, because - as Dave pointed out - Pentax allows the use of lenses, which would not communicate the max. f-stop to the camera.

These are just my thoughts, having only read the very limited information in the Dxo article.

Ben

[yeatzee]

There is a huge difference in DOF that is not well appreciated until you mount an f/1.2 lens on your camera. I would love to have one, but am too cheap.


Steve

This, except I own one

There is definitely a difference and shooting with my K 50mm F/1.2 is about as fun as it gets photography wise

Btw, glad to see more people stepping up and saying there is a difference. I remember maybe a year or two ago, everyone denied that the 50mm F/1.2's made any difference at all vs. their previous FA 50mm F/1.4's (which i sold in favor of the 1.2 ). You guys had me convinced until I bid on a K 50mm F/1.2 with a whim and a prayer, and ended up winning the auction

[RioRico]

Btw, glad to see more people stepping up and saying there is a difference. I remember maybe a year or two ago, everyone denied that the 50mm F/1.2's made any difference at all vs. their previous FA 50mm F/1.4's (which i sold in favor of the 1.2 ). You guys had me convinced until I bid on a K 50mm F/1.2 with a whim and a prayer, and ended up winning the auction

I don't recall that I ever nay-sayed f/1.2 before I got one around February this year. And I'd already had five 50/1.4's and two 55/1.4's by then (and sold off two 50's and one 55). The K50/1.2 *IS* a major boot-to-the-head after using an f/1.4 (or f/1.5 if we believe the measurement wonks about the FA50). The K50 was my second-costliest lens purchase this year, a whole US$250 and I didn't even have to fight for it. (The seller had listed it BIN at an obscure website.)

What's special about the K50/1.2? Not just the thin DOF, because you get an equivalent with an 85/2, and thinner with 135/2.8 or 200/4 or 240/4.5 or 300/5.6. And the 50/1.2 is only slightly thinner than 55/1.4. What you get is, as digitalis observed, just the best 50mm optics made by about anyone. The bokeh and sharpness and rendering etc are described above. That thin DOF is at a closer focal range than those longer thinner guys, which makes a real difference -- less feature-flattening. Different, that's the word. It's like LSD -- if you haven't tried it, you Just Don't Know.

[/me switches on the lava lamp and plays Ravi Shankar cassettes]

[Smeggypants]

Hi Everyone,
So my question is to buy or not to buy some 50 f/1.2 lens
According to DxOMark - F-stop blues
theoretically it could be no difference between f/1.2 and f/1.4 lenses.
So please help if you are those who have both lenses please make 2 photos in manual mode and check what is real benefit of 1.2 theoretically its 1/5 EV.
But 50 f/1.2 cost 5xtimes more than 50 f/1.4
So how its work on K5
Best Regards
Piotr

Just to add my views on this. I have a Pentax A 50/1.2 and an A 50/1.4.

There's something magical about the IQ on the 1.2 that is unobtainable elsewhere. Forget about theory, charts, DXo marks and other such technical stuff. There's plenty of examples of F1.2 images about which will get you excited

There's loads here Full-size sample photos from Pentax 50mm F/1.2

I don't know about 5 times as much tough. I paid £200 for my A50/1.4 and £250 A50/1.2 - maybe I was just lucky.

If you can get one, go for it. You will NOT regret it.