[yeatzee]

"everyone" was a broad generalization

edit: and yea, my FA 50mm F/1.4 cost me more than the K 50mm F/1.2 ($222). I just ended up trading it for one of my favorite lenses the F 28mm

[Digitalis]

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).

The f stop may be f/1.2 however the T-stop may be less than this - take for example the Canon EF 50mm f/1.2L which loses about T=0.9 stops of light so basically, in terms of transmittance the lens is instead an EF 50mm f/1.3L - albeit the aperture is the correct size for an f/1.2 lens, and with canons behind-the-scenes ISO boosting the shutter speeds will be the same as an f/1.2 lens - and canon almost got away with the ISO boosting. I do not suspect pentax for any behind-the-scenes ISO juggling simply because pentax has so many lenses - and a majority of them do not offer any kind of electronic coupling to pass on aperture/focal length information that if pentax tried anything like this it would be blindingly obvious to those who mix older lenses with more current lenses.

As I have said before, the SMCP-K 50mm f/1.2 is one of my all time favourite 50mm lenses on a SLR camera - and I have used more than my fair share of legendary superspeed lenses over the years.

[TOUGEFC]

And the 50/1.2 is only slightly thinner than 55/1.4.

Actually, if we are talking specifically about the K 50 1.2 vs DA*55 (both share the MFD of 45cm),
the DA*55 has the slightly thinner DOF

[Digitalis]

he DA*55 has the slightly thinner DOF

The quality of the bokeh from the DA*55mm f/1.4 isn't in the same league as the Pentax 50mm f/1.2 lenses - the only lens pentax has made that comes close to producing the extraordinary smoothness of the f/1.2 lenses is the pentax FA 31mm f/1.8 ASPH Limited

[TOUGEFC]

The quality of the bokeh from the DA*55mm f/1.4 isn't in the same league as the Pentax 50mm f/1.2 lenses - the only lens pentax has made that comes close to producing the extraordinary smoothness of the f/1.2 lenses is the pentax FA 31mm f/1.8 ASPH Limited

Thats subjective, anyway I was talking about DOF not bokeh

[Ben_Edict]

The f stop may be f/1.2 however the T-stop may be less than this - take for example the Canon EF 50mm f/1.2L which loses about T=0.9 stops of light so basically, in terms of transmittance the lens is instead an EF 50mm f/1.3L - albeit the aperture is the correct size for an f/1.2 lens, and with canons behind-the-scenes ISO boosting the shutter speeds will be the same as an f/1.2 lens - and canon almost got away with the ISO boosting. I do not suspect pentax for any behind-the-scenes ISO juggling simply because pentax has so many lenses - and a majority of them do not offer any kind of electronic coupling to pass on aperture/focal length information that if pentax tried anything like this it would be blindingly obvious to those who mix older lenses with more current lenses.

As I have said before, the SMCP-K 50mm f/1.2 is one of my all time favourite 50mm lenses on a SLR camera - and I have used more than my fair share of legendary superspeed lenses over the years.

T-stops and F-stops are two different things. F-stops are numerical values, wheras T-stops take into account other lens properties, on top of the fundamental physical ratios. I haven't measured transmission of my lenses, but as the A 50/1.2 and A/FA 50/1.4 are both of similar age ( = similar coatings) and share a 7 lenses in 6 groups design, I would expect transmission to be very similar. I think, we can forget about glass thickness or such possible minor differences with those lenses.

So, I really think, we get a genuine 1/2 f-stop difference in all respects, when switching from a Pentax 1.2 to a Pentax 1.4 lens. And even if the transmission would be different, the out-of-focus rendering would still retain the full difference between a 1.2 and a 1.4 lens.

And that some lenses do have focal lengthes deviating from the printed/engraved somewhat standardized values, does not really come as a surprise. This has been usual behaviour ever since SLR photography became popular decades ago and is well documented. Obviously this affects the f-stops as well. SO, what? As long as it is within sensible tolerances, I find this quite acceptable and without real world consequence to me.

Ben

[RioRico]

Actually, if we are talking specifically about the K 50 1.2 vs DA*55 (both share the MFD of 45cm),
the DA*55 has the slightly thinner DOF

I haven't the DA so I get to compare my K50/1.2 with a Tomioka 55/1.4 that cost 111x less (US$250 vs US$2.25). And guess what? I plug the numbers for those lenses on my K20D into an online DOF calculator and find that yes, 55/1.4 *IS* slightly thinner than 50/1.2. How much thinner? With a subject distance of 10ft, the 55's DOF is 0.01ft thinner (0.56ft vs 0.57ft).

So the difference is a factor of 0.0001x, or 1/100th of one percent. I'd call that negligible, eh? Yet I *can* see a noticeable difference between their images.

[jane7l]

as written many times on different forums: f/1.2 lenses are famous for their f/1.2 rendering, not for f/1.2 aperture...

[axl]

The quality of the bokeh from the DA*55mm f/1.4 isn't in the same league as the Pentax 50mm f/1.2 lenses - the only lens pentax has made that comes close to producing the extraordinary smoothness of the f/1.2 lenses is the pentax FA 31mm f/1.8 ASPH Limited

I wouldn't say it's in different league. Is the K50/1.2 better, definitely! But DA*55 is 2nd best in SMC labeled lenses I've tried in between 40 and 55mm.
The 2nd part is true. No arguing. 31ltd has extraordinarily smooth OOF for WA lens and makes great pairing with K50/1.2...

my 2p
---

edit:
OK, I reviewed my old shots, and it's not in the same league. 50/1.2 is simply way out there... but still, DA55 is 2nd best IMO

[nater]

The quality of the bokeh from the DA*55mm f/1.4 isn't in the same league as the Pentax 50mm f/1.2 lenses - the only lens pentax has made that comes close to producing the extraordinary smoothness of the f/1.2 lenses is the pentax FA 31mm f/1.8 ASPH Limited

Have you (or anyone you know of) done a shootout between a Pentax 50mm f/1.2 lens and the Voigtlander 58mm f/1.4? I'm curious how the bokeh compares.

[Digitalis]

Have you (or anyone you know of) done a shootout between a Pentax 50mm f/1.2 lens and the Voigtlander 58mm f/1.4? I'm curious how the bokeh compares.

the voigtlander 58mm f/1.4 has the same 0.45 minimum focus distance other pentax lenses have but due to its slightly longer focal length DOF appears to be shallower - when used on my Nikon D3s there is a visible difference between the voigtlander 58mm f/1.4 when compared to a regular Nikkor 50mm f1.4G - I also own a Noct Nikkor 58mm f/1.2 ASPH which isn't really all that fair to compare it to the voigtlander 58mm f/1.4 because the Noct nikkor is a really special lens but again there is a noticeable difference in terms of exposure and OOF rendering.

[Pentaxor]

I was one of the very few back then that have the 50/1.2, before the lens even got hugely popular and in demand. it's one of the lenses that got me into Pentax. to be honest, when I saw the f1.2 images on other photo album size, I said to myself that I need to have such lens. I think it would be pretty stupid if such rendering difference comes unnoticed. I mean, when I saw the images, I wished my f1.4s' could do that.

[jpzk]

Just to pick some brains: how does the K 50/1.2 compare to a Cosina 55/1.2? Just curious ... I own a Cosina.

JP

[Laurentiu Cristofor]

Just to pick some brains: how does the K 50/1.2 compare to a Cosina 55/1.2? Just curious ... I own a Cosina.

Rumors have it that the K is sharper wide open and that the Cosina is more like 1.4 in light transmission.

I would like to see some shots side by side though. The person that mentioned the light transmission aspect intended to do a bokeh test as well, but I never saw a follow up post - I forgot who that user was, maybe a search will bring up that post.

[Pentaxor]

Rumors have it that the K is sharper wide open and that the Cosina is more like 1.4 in light transmission.

I would like to see some shots side by side though. The person that mentioned the light transmission aspect intended to do a bokeh test as well, but I never saw a follow up post - I forgot who that user was, maybe a search will bring up that post.

actually it wasn't light transmission for the Cosina but Bokeh rendering ( bell-shapes) and a unique smoothness (a bit more buttery) and less contrast, possibly due to the extra 5mm difference. the K is more sharper, more contrast and a 1/3 advantage in light transmission. to be honest, any of those f1.2 are really good in their own respective ways.