Full review of the Sigma 50mm F/1.4 EX DG HSM lens.  Box and contents     The Sony A580 and A900 were used for this review.  For a better understanding of terms and methods used in this review, go here.   The usual center, mid-section and corner crops are located at the very bottom of the page.     Introduction.   The Sigma 50mm F/1.4 EX DG HSM lens was introduced in 2008, and is available for most major camera mounts, including Sony alpha which is tested here.  Sigma went all out and produced a fast standard prime lens that is optimized for center sharpness at F/1.4, (in my opinion) and it delivers the goods, especially when used on a full frame camera.  This lens is big, heavy and expensive, much more so than other equivalent makes and models, including the Sony 50mm F/1.4, and if you want to see some comparisons between these two lenses, scroll down to the bottom of the page.    Found on the outside of the lens is an AF/MF switch and focus distance scale under a clear plastic window, plus some depth of field hash marks (F/8-F/16) between the focus index mark.  The Sigma 50mm F/1.4 has a plastic focusing ring along with what appears to be a metal body and mount, although I didn't do any destructive testing on the lens body.  Build quality is very good, with a nice fit and finish, and it feels solid in the hand.  The lens body has an appealing black matte paint finish.  Filter size is the professional 77mm, which are more expensive, but if you own some of Sony's fast zoom lenses, you already have a few 77mm filters right?    Sigma claims the use of one aspherical element in the design of the lens.  The Sigma 50mm F/1.4 HSM says "made in Japan."   The aperture blades form a nice circle between F/1.4-9, but at F/10-16 it becomes oblong, although that's not very useful information for the average person.     The Sigma 50mm F/1.4 HSM uses a focus design that moves the front and rear optical groups down at infinity, and up at close focus, (about 8mm travel) therefore, don't set the lens bottom down without a rear lens cap when set to infinity or the rear element will make contact with the surface, and will wobble around.   The Sigma capture area is slightly greater (or "wider" by about 1-2mm) than the Sony version, which can be seen in the comparison crops at the bottom of the page.    In the box is the lens, front and rear caps, plastic petal type hood, a thoughtful (but worthless) padded carrying case and owner's manual.      Focusing.  The manual focusing ring is damped a little too much in my opinion, and is hard to turn with one finger, but It doesn't "wander" when jiggling the camera.   Focus ring travel is 1/4 of a turn form close-up to infinity, which is a good amount of travel, and allows precise focusing, but will depend on your focusing screen and eye sight.  Auto focusing; This lens uses a focusing motor inside the body, and Sigma calls it HSM or "hyper-sonic motor."  HSM is almost silent, and pretty fast, and it's better than Sony's cheap SAM system, but not better than the excellent Sony SSM system.  The Sigma 50mm F/1.4 auto-focuses accurately with my A900 however, your results may vary depending on camera and lens calibrations.  You can override the AF system in AF-S mode by simply turning the manual focus ring.     Requisite product shots. Side shot Back side showing AF/MF switch Recessed front element when focused at infinity Sigma X-ray view and MTF chart     General information and specifications. Lens Sigma 50mm F/1.4 HSM EX DG Box contents Front cap, rear cap, hood, padded case and users manual. Cost Approximately $499 Build quality Very good. Additional information Introduced about 2008.  Specifications below   Optical configuration 8 elements in 6 groups Angle of view 46.8˚ full frame,  31.2˚ APS-C  Aperture 9 blades, curved Full frame and APS-C Made for full frame, but works fine on APS-C cameras. Depth of field and focus scales? Depth of field hash marks and focus distance scale in window. Minimum focus, image plane to subject About 17.25"  (438mm) Minimum focus, end of lens barrel to subject 11.85"  (301mm)  Hard stop at infinity focus? No. Length changes when focusing? No. Focus ring turns in AF? No. Filter size 77mm. Filter ring rotates? No Distance encoder? N/A   Max magnification 0.13.5x or 1:7.4 Min. F/stop F/16 Sony teleconverter compatible? No Length changes when zooming? N/A Dimensions WxL  (my measurements) 3.35" x 2.67"   85mm x 68mm.   Maximum  extended length (my measurements) 2.67"  (68mm)                                                     Weight bare (my scale) 18.0oz  (510g) bare, with hood and caps; 20.1oz  (570g)     Optical qualities summary.     Lens flare/ghosting.  About average control.  I see mostly green colored ghosts, and some strong flare in certain circumstances, see examples below.   Light fall-off.  No problems on full frame or APS-C.  See samples below. Color fringing (CA).  Lateral color fringing control is above average and hardly noticeable.  You see some axial color fringing also when the aperture is wide open, but it clears up mostly by F/2.8, see crops in the full frame section.   Bokeh.  Smooth, but better stopped down slightly, see examples below.   Color.   seems about the same as Sony lenses.   Close up filter.  N/A       Coma.  Small amounts using an APS-C camera wide open, and strong at F/1.4 on a full frame camera, but goes away quickly by stopping down.   Regular filters cause no additional light fall-off problems using APS-C or full frame cameras.     Filter size.  77mm.  Sony lenses that use 77mm filters are; CZ 24-70mm F/2.8, 70-200mm F/2.8 G, CZ 135mm F/1.8, 11-18mm F/4.5-5.6, CZ 16-35mm F/2.8 and the 70-400mm G.   Distortion.  Minor to moderate barrel distortion on both sensor sizes.   Distortion example directly below.   Minor barrel distortion   Distortion is mild using an APS-C camera.     Light fall-off samples.              F/1.4               F/2   Light fall-off is very light and not a problem, even at F/1.4 with a filter attached.        Let's check out the macro capabilities of this lens. Below, check out the cropped image of the stamp.  The sample shot was taken with the Sony A 580 16.2MP camera.  The subject is a standard US stamp, 0.87"x 1.0" or 22mm x 25mm.  Also, note the macro shot was taken as close to the subject as focusing allowed; in this case a short 11.85" (301mm), measured from the front of the lens barrel to the subject.     This lens has an approximate reproduction size of 0.13.5x (1:7.4) which is a little small by today's standards, but it turned in a sharp image of the stamp.  The stamp shot is displayed full size, but cropped, there is no larger image.  As a side note; the "1996" on the bottom left of the stamp measures a mere 1mm wide.     As close as you can get, F/5.6. No larger image       _______________________________________________________________________     Full frame results using the Sony A900 below.   Check out the differences when using a film or full frame camera below.  I'm only pointing out the noticeable issues as compared to the APS-C bodies, so if I don't show it here, the results are not significantly different enough to warrant posting an additional set of images in this section.   Light fall-off                F/1.4               F/2   I see additional light fall-off using a full frame camera.  There is minor to moderate corner darkening at F/1.4, but it clears up nicely by closing the aperture just one stop.  Using a regular "thick" type filter produces no additional light fall-off.     Flare and ghosting control.   Sun in shot, F/5.6. Hard flare with sun out of shot, F/5.6.   Ghosting control is about average.  I see a green arrow shaped ghost when the sun is in the image, but color and severity can depend on angle and aperture.  When the sun is out of the image there are flare problems which may wipe out your image, so use your hand as a light block, which works better than the included hood.     Full frame distortion.   Minor to moderate barrel distortion on A900   I see some additional barrel distortion with full frame coverage, although not really a simple curve, it's still fairly easy to fix in post processing.     Bokeh samples.              F/1.4              F/2            F/2.8              F/4   Bokeh looks pretty smooth at all apertures, however, I see some spherochromatism at F/1.4, which causes that aperture bokeh to look less smooth than at other apertures.  Spherochromatism shows itself as colored tinges around blurred highlights, such as when the foreground is blurred, you'll get red outlined highlights, with the background blurred, you'll get green outlined highlights, (see F/1.4 crop above), this usually goes away as you stop down, and is mostly noticeable on fast lenses when used wide open.  Worth mentioning; at certain de-focused distances, highlight blur along the image sides at F/1.4-2 is triangular is shape, and looks harsh, but that's not unusual with fast lenses at those apertures.   Coma              F/1.4              F/2            F/2.8              F/4   Coma is strong on a full frame camera when the aperture is wide open, but stopping down gets rid of this quickly.  The F/2.8 full frame crop above is what you would see at the corners of an APS-C cameras with an aperture of F/1.4.  The subject is a small Christmas tree with lights.   Axial color fringing.              F/1.4              F/2            F/2.8              F/4   Axial color fringing can occur anywhere in the image, but goes away as you close the aperture.  The crops above where taken from the image centers, and show somewhat strong magenta coloring at F/1.4, but just one stop down and it isn't so noticeable.  This is typical results for a fast lens.   Size comparison.   Quick snap showing the size differences of the two 50mm F/1.4 lenses.   This is a crappy after-thought picture showing the size differences between the Sigma and Sony lenses.  I took this quickly before I had to send the Sigma lens back!          Conclusion.    The Sigma 50mm F/1.4 HSM is expensive, but has a very good build quality, well implemented HSM focusing, and provides excellent center sharpness at F/1.4.  Other areas that rate well are light fall-off, lateral color fringing and to a lesser extent coma, although I was a little surprised at the full frame coma size at F/1.4.   If you've looked at the crops below, you'll see just how sharp the Sigma is at F/1.4, especially when you compare it to Sony's version.  As you move away from the center area, the Sigma softens up, and eventually compares evenly with the Sony around F/5.6.  In other areas, like coma, the Sigma shows strong amounts at F/1.4, but less than the Sony at all apertures.  Color fringing and bokeh are about the same on each lens.   The Sigma 50mm F/1.4 HSM seems to be best when used on a full frame camera, as there is little penalty for the additional coverage, meaning the corners are about the same as the mid-sections stopped down some.  The centers at F/1.4-2 seem sharper when using the A900 as opposed to the A580, although I didn't compare them in a direct manner.   For APS-C users; I'd recommend the Sony 35mm F/1.8 over the Sigma, although not as fast, it covers about the same area, and performs about the same, but is smaller, lighter and much less expensive.   Landscape shooters will probably not gain much if anything by switching to the Sigma from the Sony, as both are about the same in optical performance at F/5.6 and beyond; additionally, the Sony is much smaller and more pocketable than the huge Sigma.   If you're looking for a 50mm lens with excellent low light, hand held performance, especially wide open, the Sigma 50mm F/1.4 HSM is your lens; it does seem to live up to the hype, and is worth the price in my opinion.

	Center	Mid-section	Corner
F/1.4
F/2
F/2.8
F/4
F/5.6
F/8
F/11

The wide open centers are really sharp, however, once you leave the centers, the image softens up noticeably.  The mid-sections are reasonably sharp at F/4, with the corners requiring about a stop more.  The optimum landscape aperture seems to be F/5.6, with F/8 showing some softening due to diffraction.  Exposure differences are from light fall-off.  Distance to subject is about 200' (200m).   Please check out the Sigma 50mm F/1.4 HSM at B&H Photo and help support the site!     ___________________________________________________________________________________________________________________________   Bonus section.   I've worked up a direct comparison using the Sigma 50mm F/1.4 HSM and Sony 50mm F/1.4 lenses.  The distance from camera to subject is about 200' (200m).  The Sony A900 was used for this comparison.  Bracketed manual focusing was used, with the resulting absolute sharpest shot used as the base for the entire set, for each lens.  Exposure differences are from light fall-off.  All camera settings were the same for each lens.   Centers               Sigma 50mm F/1.4 HSM           Sony 50mm F/1.4 F/1.4 F/2 F/2.8 F/4 F/5.6 F/8 F/11   The center crops really show how much sharper the Sigma is at large apertures, but the differences disappear by F/5.6.  You should also note the coverage differences between the two lenses, the Sigma is slightly wider.   Mid-sections               Sigma 50mm F/1.4 HSM           Sony 50mm F/1.4 F/1.4 F/2 F/2.8 F/4 F/5.6 F/8 F/11   The differences in the mid-sections aren't as apparent as the centers.  I see the Sigma is a little sharper at wide apertures, but both are about the same from F/2.8 on down.   Corners               Sigma 50mm F/1.4 HSM           Sony 50mm F/1.4 F/1.4 F/2 F/2.8 F/4 F/5.6 F/8 F/11   Other than light fall-off, I don't see a whole lot of differences between the corner crops, although the Sigma seems a little sharper at most apertures.   That's it, I hope you enjoyed the comparison.