[JinDesu]

I recently got a DA*55 F1.4 and felt that it was very comparable in sharpness with my Sigma 50 F1.4. Following this are some comparison pictures between the two lenses.

Disclaimers:
Tests were done on tripod using 3 second remote shutter. Setups are not scientific - I've tried to keep the subjects the same, as much as possible. I have also tried to keep the focus the same, but it is very very difficult at F1.4. I process everything in Lightroom using +15 clarity, 45 sharpness, 45 detail, 1 radius, 0 masking. That is my standard template for all my pictures. All my shots are done with the proprietary hood. I've had my Sigma 50 F1.4 (only owner) for about 2 years now, and the DA*55 F1.4 (second owner) for about 1 month.

Shots were done using Av mode, so some of them are darker or brighter. With my k-x's single dial, it was a lot more work to manually change the shutter and aperture to achieve the same exposure (and at 1/3 stops, it's not exact anyways). I wanted to minimize the amount of motion I induced in the camera that would shift the tripod.

I have completed the first sequence this evening. I will try to do a few more, but maybe I get lazy or something and take a while. Also it's cold in NYC right now, so it's not so easy to go out for landscape shots.

First sequence - focus point on the stage-left eye (left eye in the image):
Please let me know if the images are a bit dark - I have two monitors and I edit on the better one (which is brighter), but I realize not everyone uses the same monitor or settings as I do.

Sigma 50 F1.4
@F1.4
http://farm4.staticflickr.com/3720/11830363146_b82f153c9a_o.jpg

@F2
http://farm4.staticflickr.com/3755/11830361726_eb07945234_o.jpg

@F2.8
http://farm4.staticflickr.com/3707/11829566245_3da9e0164f_o.jpg

@F4
http://farm4.staticflickr.com/3779/11830358466_a91656d33c_o.jpg

@F5.6
http://farm6.staticflickr.com/5487/11829562885_792e9632d6_o.jpg

@F8
http://farm4.staticflickr.com/3759/11829979844_137e592706_o.jpg

DA*55 F1.4

@F1.4
http://farm3.staticflickr.com/2830/11829559855_fcbd219a87_o.jpg

@F2
http://farm8.staticflickr.com/7330/11829558085_4292f59c4a_o.jpg

@F2.8
http://farm6.staticflickr.com/5524/11830350516_ffb743aa30_o.jpg

@F4
http://farm4.staticflickr.com/3728/11829973114_f597e10568_o.jpg

@F5.6
http://farm3.staticflickr.com/2866/11829552285_390e1d41d1_o.jpg

@F8
http://farm4.staticflickr.com/3791/11829824103_e22b144056_o.jpg

Thoughts and conclusions
Let's start with bokeh first. I've seen quite a few posters state that the DA*55 has better bokeh than the Sigma 50 F1.4. In truth, when using the Sigma 50 F1.4, sometimes the bokeh gets a little distracting. I chalked that up to the fact that the backgrounds were exceptionally difficult to render. In this shootout, it was difficult getting the background to be the same, since the DA*55 is a different focal length. I did my best however, and my conclusion is that at the large apertures - the Sigma 50 F1.4 has slightly smoother bokeh, but much uglier specular highlights. The onion ring highlights are very distracting and the DA*55's specular highlights are much more even.

For sharpness - at F1.4, the focus is just a little bit off in both shots. The DA*55's focus is a bit further back, while the Sigma's is a bit front. I have, however, captured the eye in focus regardless so we can try to make the comparison. From my view, the DA*55 wins the center sharpness at F1.4. My Sigma 50 F1.4 has the wide open bloom that a lot of people have experienced. My DA*55 does not have that bloom at all. If i were to make a guess, I would say that the more substantial hood on the DA*55 has some effect on this. This remains true for F2 as well.

At F2.8 and upwards, the Sigma catches up in center sharpness and they are both neck and neck here. This performance of the Sigma matches what Lenstip and Photozone have shown for the lens resolution. F2.8, F4, and F5.6 are really close in performance and are much better than F2. The DA*55's performance on Lenstip and Photozone also show a big increase at F2.8, but I think I have a pretty good copy because F2 performs so well.

I really like my DA*55. I might have a weaker copy of the Sigma 50 and a better copy of the DA*55, but regardless both lenses are great. When I can resolve individual threads at F1.4, I am happy with the lens. I suspect the new Sigma 50 F1.4 coming out will edge out both these lenses - but the WR of the DA*55 is what I value.

Some 100% crops for reference (click for full size):
Sharpness crop:


Bokeh crop:


Usage/Personal preferences
Having used both lenses, and having used the Sigma 50 F1.4 longer, I have a great appreciation for the DA*55. It is smaller, lighter, and nicer to the touch. The focus ring is very smoothly damped and is easy to focus with. The Sigma's focus ring is tighter and has a shorter throw, making it harder to focus. The hood on the DA*55 is very well built and is a nice plastic. The Sigma's hood is not as sturdy and feels cheap. It also doesn't have that nice velvet interior. The plastic on the DA*55 has a better texture than the one on the Sigma. Also, cleaning the front element on the DA*55 is a bit easier

The HSM on the Sigma is faster and quieter than the DA*55's SDM. Part of it is the shorter focus throw, but the speed difference is definitely noticeable. The SDM has little squeaks as it gets into place, which I hear is normal (almost inaudible, but definitely more audible than the Sigma). The Sigma will squeak very lightly if it's shuddering into place in low-light.

For looks, I am biased towards the flashy DA*55. The gold ring, the green ring, the gold text, red star & text, fancy gold rimmed focus distance window, etc. Just a much prettier lens when compared to the Sigma 50 F1.4. Price - well the Sigma is a bargain. At $350, it's a fantastic lens that is pretty much equal to or better than any other equivalent (excepting the Otus and the soon-coming replacement). The DA*55 is quite expensive at $600-700 - which is a bit much to pay for the weather sealing. WR is something I prize, however, so I am willing to spend the difference.

I didn't talk about color and microcontrast etc because I am not technical enough to provide the differences. That being said, the shots I have gotten recently with the DA*55 have constantly wowed me, more so than my Sigma 50 has ever done. For some reason, things "pop" better and are prettier than when using the Sigma 50. Perhaps this is just a color profile to set, but I'm a bit lazy and I appreciate that the DA*55 does it automatically for me.

A final image to show the prowess of the DA*55:

Shot from about 30-40 feet away at F1.4:

Full size image: http://farm8.staticflickr.com/7385/11429762316_4a7bddaed0_o.jpg

I was amazed not only by the center sharpness, but also the corner sharpness at F1.4.

[JinDesu]

Reserved for future posts.

[JinDesu]

Another one reserved for future posts.

[VisualDarkness]

The DA* is really good, I agree. I really thought the Sigma was as sharp though but the difference is clear here at larger apertures.

[JinDesu]

I may have a weaker copy of the Sigma and a better copy of the DA* - as they are so close in sharpness that the sample variations can be the difference.

[sTi]

My Sigma 50 F1.4 has the wide open bloom that a lot of people have experienced. My DA*55 does not have that bloom at all. If i were to make a guess, I would say that the more substantial hood on the DA*55 has some effect on this. This remains true for F2 as well.

I don't think it's related to the hoods. The reason for the difference is probably due to how spherical abberation is corrected at large apertures. The Sigma seemingly has slightly under-corrected spherical abberation, which leads to smoother bokeh (and smoother specular highlights without outlining), but as a side-effect suffers from a certain haziness and lower contrast wide open. The DA*55, in contrast, seemingly has slightly over-corrected spherical abberation at large apertures, which eliminates the haziness but leads to more nervous bokeh due to the light distribution in the circles of confusion. This leads to more nervous bokeh and can e.g. be seen in the specular highlights, which are brighter at the outside than at the center. This is the price we have to pay for the excellent sharpness and contrast already at f/1.4 . Used rightly, however, the somewhat weird f/1.4 bokeh can even support a surreal, impressionistic effect with a suitable background. I've seen several examples here on PF where people have used this bokeh characteristic to great effect. But in other instances, it may only looks harsh
Fortunately, the bokeh is already much smoother at f/1.8, so it's no big deal IMO.

By the way, the "onion-ring" look of the Sigma's specular highlights is caused by imperfectly polished aspherical element(s).

[Rondec]

I don't think it's related to the hoods. The reason for the difference is probably due to how spherical abberation is corrected at large apertures. The Sigma seemingly has slightly under-corrected spherical abberation, which leads to smoother bokeh (and smoother specular highlights without outlining), but as a side-effect suffers from a certain haziness and lower contrast wide open. The DA*55, in contrast, seemingly has slightly over-corrected spherical abberation at large apertures, which eliminates the haziness but leads to more nervous bokeh due to the light distribution in the circles of confusion. This leads to more nervous bokeh and can e.g. be seen in the specular highlights, which are brighter at the outside than at the center. This is the price we have to pay for the excellent sharpness and contrast already at f/1.4 . Used rightly, however, the somewhat weird f/1.4 bokeh can even support a surreal, impressionistic effect with a suitable background. I've seen several examples here on PF where people have used this bokeh characteristic to great effect. But in other instances, it may only looks harsh
Fortunately, the bokeh is already much smoother at f/1.8, so it's no big deal IMO.

By the way, the "onion-ring" look of the Sigma's specular highlights is caused by imperfectly polished aspherical element(s).

Yes, I seldom shoot the DA *55 wide open due to the bokeh, but stopped down to f1.8 smooths it out really well (and it is quite sharp there).

[rob1234]

The DA*55 is one of the main reasons I am staying with Pentax - my favourite lens. As others have said, half a stop down it is at it's best I reckon.

[JinDesu]

I don't think it's related to the hoods. The reason for the difference is probably due to how spherical abberation is corrected at large apertures. The Sigma seemingly has slightly under-corrected spherical abberation, which leads to smoother bokeh (and smoother specular highlights without outlining), but as a side-effect suffers from a certain haziness and lower contrast wide open. The DA*55, in contrast, seemingly has slightly over-corrected spherical abberation at large apertures, which eliminates the haziness but leads to more nervous bokeh due to the light distribution in the circles of confusion. This leads to more nervous bokeh and can e.g. be seen in the specular highlights, which are brighter at the outside than at the center. This is the price we have to pay for the excellent sharpness and contrast already at f/1.4 . Used rightly, however, the somewhat weird f/1.4 bokeh can even support a surreal, impressionistic effect with a suitable background. I've seen several examples here on PF where people have used this bokeh characteristic to great effect. But in other instances, it may only looks harsh
Fortunately, the bokeh is already much smoother at f/1.8, so it's no big deal IMO.

By the way, the "onion-ring" look of the Sigma's specular highlights is caused by imperfectly polished aspherical element(s).

Thanks for this technical explanation, it's very helpful!

[HSV]

I own both and from my experience, I would use them in different applications.

I find that the bokeh and sharpness of the DA55 is more suited for environmental portraits and overall people photography. The sharpness of both lenses are excellent and at a real sharpness test (measuring resolving power), both of them are neck to neck...but for some reason, at least in my copies, the Sigma seems to have more microcontrast, which gives an impression of being sharper overall than the DA (in the overall picture, not pixel peeping).

At larger apertures, the Sigma is very prone to bokeh fringing and it flares easily...which I think is true of all modern Sigma lenses, at least in K mount. The rendering is colder and less saturated. I don't like the look of it for people (which is most of what I do nowadays), so I end up not using this lens as much as the DA.

[JinDesu]

I'll try to do a flare test between the two once it warms up, I know that my Sigma's flare doesn't look so bad from some angles. The starburst of my DA* is better though.