Sony A6500

The Sigma 23mm f1.4 DC DN lens was introduced in April 2023 for APS-C cameras in Sony E, Leica L, Fujifilm X and Canon RF mounts and currently sells for $750 AUD. The focal length gives a full frame equivalent of 35mm and it joins the 16, 30, and 56mm lenses which means that there are now f1.4 primes in 24, 35, 45, and 85mm full frame equivalent focal lengths. I’m looking at the Sony E mount version which I bought in May 2024 primarily to use for video mounted to my Sony A6500. I’ve only recently started using it as a general purpose walk around lens.

Vital Statistics

Mount	Sony E, Leica L, Fujifilm X, and Canon RF
Lens Construction	13 elements in 10 groups with 3 Special Low Dispersion glass and 2 aspherical elements
Angle of View	63.4º
Number of Diaphragm Blades	9 rounded blades
Minimum Aperture	f16
Minimum Focusing Distance	25cm
Maximum Magnification Ratio	1:7.3
Filter Size	52mm
Dimensions	65.8mm ⦰ x 78.9mm (h)
Weight	330g for Sony E mount version
Supplied Accessories	Petal shaped lens hood

The Sigma 23mm f1.4 DG DN is part of Sigma’s Contemporary line which means it has a utilitarian plastic body (or as Sima prefers to call it a Thermally Stable Composite). The only external control on the lens is the ribbed focusing ring which is of the “fly by wire type”. The lens is advertised as being dust and splash proof, but the only sealing is at the lens mount where there is an “O” ring seal. The lens mount itself is chromium plated brass for longevity. It is still good to see this as other manufacturers are tending to use plastic mounts on their budget lenses. The lens is supplied with a plastic petal shaped lens hood which feels very well made and it attaches by a bayonet fitting to the lens. It feels secure and well made.

Physically the Sigma 23mm is quite a large lens. Not as big as the Sigma 16mm f1.4, but bigger than the Sony 28mm f2 and Sony 50mm f1.8. The weight of the lens is 330g – the Sony E mount version is the lightest at 330g and the Canon RF is the heaviest at 345g – and it contributes to the lens having a satisfying heft in the hand. The whole thing is well put together with no dodgy looking seams in the composite body or creaking and flexing when you give it a squeeze. While not part of Sigma’s more premium Art and Sports lines the Sigma 23mm feels a quality piece of kit.

The Sigma 23mm f1.4 DG DN has an optical construction of 13 elements in 10 groups with 3 Super Low Dispersion (SLD) elements to reduce transverse chromatic aberration and 2 aspherical elements to provide correction of spherical aberration and field curvature. The diaphragm sports 9 rounded blades and while not having the eleven blades that the Art Series primes have this does produce nice bokeh effects – more about which later. The minimum focusing distance is 25cm measured from the sensor plane which gives a maximum magnification ratio of 1:7.3.

Optical Performance

I must say I was quite impressed with the optical performance of the Sigma 23mm f1.4. Wide open the centre is sharp and the corners are a tiny bit softer and have less contrast. Stop down to f2 and things significantly improve. The centre gets even sharper and there is more contrast and the corners now match the centre. Quite something. This performance stays constant until f11 where diffraction starts to set in and the image softens.

Chromatic Aberration

Axial chromatic aberration, also known as longitudinal chromatic aberration is present when the lens is wide open, but it is very well controlled and barely noticeable. Stopping down fixes the problem.
Transverse or lateral chromatic aberration is present, but it is very slight and you really have to pixel peep to find it or turn off the lens profile.

There is some very slight barrel distortion present, but you have to turn off the built in lens profile to really see it.

When it comes to flare and diffraction spikes it is a bit of a mixed bag. The good is that there is no evidence of any veiling flare. Polygonal shapes and light streaks are visible. The diffraction spikes or sun stars are quite nice and defined.

The nine curved diaphragm blades produce nice clean bokeh balls with no evidence of the soap bubble effect or onion rings at the centre of the frame when wide open. At the edges they take on a more elliptical shape. At f2.8 and beyond the circles start to take on a more polygonal shape. The rendering of the out of focus areas and the tonal transitions are beautifully smooth.

Autofocus Performance

The complexity of modern autofocus systems in mirrorless cameras means that much will depend upon the AF settings you have made on your camera. A casing point is that when testing this lens on my A6500 the initial results looked very poor. So poor in fact that I put the lens on my A7r2 in APS-C mode and repeated them and the results were like night and day. A quick examination of the A6500’s menu found that I had previously been experimenting with the AF settings and hadn’t put them back to how they were. Once restored it was like looking at a totally different camera and lens combination.

Shooting stills I tested the lens by walking towards the camera with continuous AF set and the lens easily kept up with my movement. It was only when I got close up that there was any sign of hesitancy, but it still managed to find focus. Averaging out several test runs I was getting a hit rate of 93% with critical focus and 7% with acceptable focus. An impressive result.

Shooting video the results weren’t as positive and the lens had trouble keeping up with me as the target. But, when I mounted Gary the Galah to a slider and set it to a 10 second run while close to the camera the AF was very sticky and accurate.I would expect that the A6700 with its more sophisticated subject tracking AF system would yield a better result here. Focus pulls using touch to focus were very decisive with no overt hunting.

While we are talking about focusing I looked at the focus breathing it was very evident.

Verdict

Well after using the Sigma 23mm f1.4 DG DN for a year I can say that I have found it be a very capable lens. For video it is near perfect for filming talking head pieces for YouTube – which is what I mainly use it for. For photography it is a great carry around lens suitable for street photography and urban landscapes. I’d happily travel with it as my only lens as well. Does it have any short comings? Well if I were to nitpick some people might find that the lens makes the camera a little front heavy. It doesn’t bother me in the slightest, but these sorts of things can be a deal breaker for some.

Who should buy it? Well that depends upon which camera ecosystem you’re in. If you have an APS-C Canon RF camera and want a fast moderately wide lens then this is your only choice. For Sony and Fujifilm owners it is a little more nuanced. Both manufactures have their own version of this lens. Sony has the Zeiss 24mm f1.8 which retails for $1500 AUD. It can focus a little closer but has a slower maximum aperture and is getting a little long in the tooth. Fujifilm has two competitors. The XF 23mm f1.4 R LM WR lens which retails for $1500 AUD which has better close focusing and superior weather sealing. Then there is the XF 23mm F2 R WR at $640 which also focuses closer, has better weather sealing and is cheaper while having a slower maximum aperture. If you want a fast maximum aperture at a reasonable price then the Sigma can’t be beat.