sigma-30mm-f28exdn

Introduction

With the announcement of Sigma 30mm f/2.8 EX DN, along with its sister Sigma 19mm f/2.8 EX DN, Sigma Corporation has finally made its long anticipated entrance into the mirrorless lens market official. Both lenses were announced in early 2012, with the 30mm lens making its roadways to dealers in late March. The lens is available for both m4/3 as well as Sony NEX mounts and costs $199.

The optical construction of the lens consists of 7 elements in 5 groups. The build quality and finish of the lens is quite cheap - all plastic barrel with knurled plastic focusing ring. The lens is fairly small and light, measuring only 60.6x36.6mm (2.4x1,5in) and weighing only 135g (4.8pz). The lens accepts 46mm screw-in type filters and has the minimum aperture of f/22. Aperture levels are controlled electronically from the camera. The minimum focusing distance is 30cm (11.8in).

 

View 1

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View 2

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The manufacturer's box includes the lens, front and rear caps and registration card. Within the scope of this review, the lens was tested on a 16Mp and 24Mp APS-C type Sony NEX-5n and Sony NEX-7 cameras.  

Summary

Lens Composition 7 elements in 5 groups
Angular Field 50 degrees (Sony NEX)
Minimum Focus 30cm/11.8in
Focusing Action AF/MF
f-stop Scale f/2.8-f/22, electronic
Filter Size 46mm
Lens Hood N/A
Weight 135g/4.8oz
Dimensions 60.6x38.6mm/2.4x1.5"
Lens Case Soft pouch (included)
Retail Price $199 (2012)
Depreciation -$50 (2012)


Handling

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Like virtually all Sony E mount lenses, Sigma 30/2.8EX DN follows a minimalistic, bare-bone, consumer type of an approach to the design and handling. Absent are distance and DOF scales, aperture ring and lens hood. There is no built-in optical stabilization system either. To keep the price low, Sigma seems like went out of its way to use as cheap materials as possible - unlike Sony E mount lenses, which sport a lightweight aluminium finish, Sigma's lens is all plastic. But, again, short of trying to bang your lens on a rock, the lens looks and operates just fine. At the same time, the lens is about 1/3rd shorter than Sony's 30/3.5 Macro lens, making it a more compact (and faster) choice for those looking for a street-type photography.  

Sigma 30/2.8 EX DN supports both AF as well as manual focusing, AF is reasonably fast, taking ~1 to 1.5 seconds to lock on target, although AF feels sluggish at times and at times noisy. Full AF in movie mode is also supported. The focusing ring does not have a limiter and rotates freely in either direction, although there is about 75 degrees of true rotational thrust for the lens to go from the infinity to the MFD. As is the case with most contrast based AF systems, Sigma would end up hunting for focus in dimly lit and low contrast environments, sometimes locking out of focus completely.    


 

Resolution

Given the rather ho-hum resolution performance of Sony's native E 30/3.5 Macro lens, particularly on the NEX-7 camera, we were quite curious about performance of the Sigma lens. After all, this is the first true competitor to the Sony's native lenses, and actually a very attractive competitor both in terms of price as well as (paper) characteristics.

After running the lens through a series of tests, it's safe to say that it does perform better than Sony's E 30/3.5 (at least in resolution department). Not significantly, but still better. If we look at the side by side comparison, Sigma edges a victory around corners, where it is consistently better than the E 30/3.5 Macro. But, if we look at the lens in isolation, its performance is, while decent, not necessarily jaw-dropping. Center sharpness is superb throughout the tested apertures and both on NEX-5n as well as on NEX-7. Border image sharpness is fairly good too, but clearly lags center in quality. Moreover, while borders improve with stopped down apertures, improvements are rather marginal - depending on the point of view, you can argue that performance is very uniform (which would be a 'glass half-full' point of view) or you can argue that there is no improvement at lower apertures (which would be a 'glass half-empty' point of view).  

 

MTF50 (Sony NEX-5n)

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MTF50 (Sony NEX-7)

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LW/PH (Sony NEX-5n)

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LW/PH (Sony NEX-7)

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But the improvement in resolution over Sony E 30/3.5 seems to be quite eluding when it comes down to print quality. If we look at the SQF charts produced by the Imatest, we can see that the the improvement is not sufficient to produce higher quality 24in prints - both NEX-5n as well as NEX-7 are expected struggle, particularly around borders.

 

SQF Sony NEX-5n

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SQF Sony NEX-7

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The imaging target corner crops below demonstrate what we have to work with. Sharpness on NEX-5N looks fairly good both wide open as well as stopped down, but quality at f/2.8 degrades on NEX-7, making corners look smudgy.  

 

Sont NEX-5n

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Sony NEX-7

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Before making our final conclusions about the sharpness of the lens, let's take a look at the usual infinity shots done with NEX-7 camera (uncorrected for artifacts). We can see that there is basically no difference in the center between f/2.8 and f/8 that can be detected visually. Borders, on the other hand, do show a little bit of softness at f/2.8, which is in line with what Imatest seems to be thinking. Overall though, image quality does not seem to be particularly bad and is likely going to be perfectly acceptable to majority of users.

 

Center

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L.L.Corner

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U.R.Corner

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Color & Rendering  

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There is nothing really extraordinary that can be said about Sigma's 30/2.8 EX DN lens in this section. The lens performs reasonably well with basically no major flaws, but nothing really that would make this lens stand out in a league of its own.

Color palette is well balanced and neutral (assuming you're shooting in RAW and Adobe RGB color space, which gives you a little bit more color gamut coverage). Global contrast levels are also average throughout most aperture levels, although there is a little bit of degradation at close focusing distances. Tonal reproduction is fairly decent - again nothing that would make this lens stand out but sufficient to give you enough flexibility in post-processing.

This is actually an interesting trend that has started to develop lately. A whole range of new, lower priced lenses like Sigma 30/2.8 delivering fairly solid performance that would besuitable for the majority of users out there. We clearly have not reached a breaking point in lens prices, given the recent hikes from Sony, Nikon, Leica and other manufacturers, but it seems that a new segment of reasonably prices, but still performing quite well lenses is under development. Think about it. At $199, Sigma managed to incorporate a linear AF motor, add a double-sided aspherical element and apply multi-coating ot the lens. A similar entry level lens from Canon, the 50/1.8 Mk2 lens costs even less - $155 after a price hike a few years ago. Or Samyang's 85/1.4 and 35/1.4 lenses, which created their own share of uproar due to their high optical performance. Bottom line is that this is a welcoming trend, and hopefully it will continue to expand so that more users can experiment with a larger variety of fairly decent, yet inexpensive lenses. Digressing....

Going back to the Sigma - as mentioned in the paragraph above, the company has added two aspherical surfaces (single element) to the lens design in hopes of reducing various forms of chromatic aberration. Despite that, the lens does produce some lateral CA though. In the Imatest benchmarking, Sigma clocked CA of ~1.2px on NEX-5n and ~1.6px on NEX-7. This means that you should expect some color fringing around high contrast areas - those would be visible under high magnification, but are unlikely to cause issues with prints. Longitudinal CA on the other hand is minimal to non-existent. There is a little bit of light bleeding that can be noticed in higher contrast areas, for example in night shots with brightly lit bulbs, but this artifact is also quite benign.

 

Lateral CA

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DOF & Bokeh      

Given its moderately fast aerture, Sigma 30/2.8 would not dazzle you with a creamiest OOF rendering out there. For those purposes, get something faster, with shorter MFD or longer FL (or all of the above). Still, on an APS-C sized NEX cameras, the lens gives you a DOF of 1.02cm at the MFD - not too shabby for most purposes. Bokeh feel with this lens is fairly neutral - OOF highlights retain even illumination and there are no noticeable harsh edging to highlights. As mentioned, contrast levels seem to be a little bit lower at the MFD, but that sort of becomes a non-issue in practical use.

 

DOF @ 40cm

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f/2.8

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f/4

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f/8

 


 

Flare      

Flare control is basically average in this lens. Under the worst lightning conditions, like showcased in the samples below, you should expect a fairly heavy amount of flare, some aperture ghost, color bands and greatly reduced contrast. Sigma did not supply a lens hood with this lens, but it's not like you'd be able to use a lens hood with the lens anyway - the lens does not have a hood bayonet at all. The only option is if you manage to find a 46mm screw-on type lens hood, but I'm not even sure such lens hoods exist.

 

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Vignetting

Sigma 30/2.8 showed some vignetting on NEX-7 - at ~1.5EV with wide open aperture, you would notice darkening of corners in lightly colored scenes. Stopping down to f/4 brings light falloff to ~0.85EV and by f/5.6 vignetting is basically gone.

 

Vignetting, uncorrected (Sony NEX-7)

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Camera's built-in shading correction does remove some portion of vignetting, but not completely - still better than nothing. If you choose to correct vignetting in post-processing, you would need to set vignetting correction to +25 for f/2.8.

 

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Distortion  

Sigma 30/2.8 EX DN showed a pretty minimal amount of barrel distortion - at ~0.5% distortion should not be visible under real life situations.

 

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Macro  

Sigma 30/2.8 DN is not particularly well suited for macro photography because of its dismal max magnification of 0.12x at the MFD. The lens suffers a little bit in sharpness at its widest aperture, but only a little bit. With the EFOV of 45mm, the lens turns into a normal-ish prime, so it's would not be out of question to shoot it at the MFD to get the shallowest DOF

 

30mm @ f/2.8 (30cm)

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30cm @ f/8 (30cm)

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Coma  

Sigma 30/2.8 EX DN showed moderate degree of coma around corners at f/2.8, which is reduced with stopped down apertures. By f/8 it is very minimal to non-existent. The crops below demonstrate what you can expect with the lens - images were taken at ~1.5m focusing distance and 3s exposure time.

 

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Alternatives

The most obvious alternative to Sigma's 30/2.8 EX DN is Sony's own E 30/3.5 Macro prime. However, it's not really a direct comparison since Sony's lens is more of a specialist, being a macro lens and all. Other than that, there are not other 30mm primes and you would either need to go wider or longer. Sony branded Carl Zeiss Sonnar 24/1.8 ZA lens is an excellent choice if you're willing to go wider than 30mm, while Sony's E 50/1.8 OSS prime is another good choice for longer FL needs. Otherwise, look for alternatives. If you have Sony's LA-EA1 or LA-EA2 adapter, you can use any of the currently manufactured Alpha mount lenses, including Sony DT 30/2.8 Macro, Sigma 30/1.5 EX DG or Sonny AF 28/2.8. Older Minolta lenses like Minolta AF 28/2.8 might be an option as well.  

 

Recommendation

If you were considering Sony's E 30/3.5 Macro as a general purpose, walk-around lens, forget that idea and go get Sigma 30/2.8 DN instead. Sigma's first entrance into the NEX world is fairly solid and its first native mount NEX lens edges over its chief competitor in pretty much all aspects except macro photography. Faster by almost a full f-stop than Sony, with slight improvements in resolution (specifically around borders) as well as cheaper price point (particularly when we consider the latest price hike on Sony lenses), Sigma offers a very attractive package in this lens. Like any lens, Sigma 30/2.8 EX DN is not without flaws - vignetting and CA might still bother some photographers. What else is there to say? Go get the lens...   Sample Images  

 

Sample Images

 


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