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Sirui AF 75mm f/1.2 - Lightweight Portrait

Sirui have been making lenses for around a decade now and their trinity of f/1.2 APS-C auto focus "Sniper series" lenses (23, 33 & 56mm), which came out last year, just got expanded with a 16 and 75mm. The latter being the most interesting to me (for wildlife and bokeh panoramas) with its full frame equivalency of 113mm f/1.8. Weighing a mere 425g it's the lightest lens of its type by far (as well as amazing value - €300). Let's see how much I can cut the weight of camera down by and what impact it will have on image quality...

Sony A5100 | Ducati | 41 image Bokeh Pano

 

Size & Weight

I really like 135mm lenses for photographing friendly wildlife. They give me a little reach (to keep some distance), while having fast apertures (for poor light / good subject isolation) and being relatively small (compared to a 70-200mm). This Sirui lens provides very close results to the full frame setup I am used to, while cutting the weight of the system in half! Saving weight with smaller sensor cameras usually comes at the expense of subject isolation (depth of field) and noise, due to smaller entrance pupil lenses, but not here!

Lens Entrance Pupils Compared

Sirui has managed to get this lenses size and weight down to that of an 85mm f/1.8, which is especially impressive when you realize its entrance pupil is larger than an 85mm f/1.4. Being a crop lens this a closer to something like a 105mm f/1.8 on full frame. This is still an unusual lens, but Nikon used to make an AI-S version. Compared to that the Sirui 75mm is: Smaller, lighter, sharper and faster while adding good auto focus and costing less new than what the second hand Nikon lenses tend to in worn condition!

 

Read on and judge the images for yourself, but I feel like this Sirui lens is capable of some pretty impressive results that rival much larger modern optics. Never before has "Having your cake and eating it" been so achievable - losing the crop sensor penalties, but keeping the size, weight and cost advantages. What kind of wizardry is this?

Sony A1 (full frame) | Red Squirrel | f/1.2, ISO 800

 

Image Quality

The above full frame image (shot @ f/1.2) shows how much extra you can get from the crop lens and where where the vignette starts to creep in. Manually correcting this (on crop / wide open) required the lowest amount of adjustment that I have seen from a fast lens like this. Mechanical vignetting (cats eye shaped bokeh shapes in corners) was quite noticeable, but not worse than most fast full frame lenses. There is quite strong lens flare, but chromatic aberration is quite well controlled.

 

So, is the image quality any good? The short answer is yes, sharpness generally delivers. The first caveat is a technical one on my part - there are no high pixel density Sony APS-C cameras to properly test this. 26mp is the highest resolution and I only have a 24mp one. To get the above image I used a 50mp full frame Sony A1, which provides 21mp from the crop area. The lens seems to max all these sensors out, which is great, but I can't say how this would be on a modern 40mp Fuji APS-C sensor.

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Sony A1 | Baby Squirrel | f/1.2, ISO 200

There is a drop in sharpness when focusing very close and the aperture is wide open, although this is quite normal. Any closer than 1m (MFD is 69cm) I found stopping the lens down to f/1.6 improved the results nicely. Very out of focus backgrounds look pretty good and clean, however the transition from in focus to slightly out of focus specular highlights can look rather busy and less smooth (see squirrel image below). It's worth noting that this was only observed on the full frame Sony with electronic shutter, so I will keep experimenting with this to see if that had a baring on the effect.

Sony ZV-E10 | Baby Woodpecker | f/1.2, ISO 1000

 

Focusing

The 69cm minimum focus distance is great for wildlife. Matching the Sony 135GM lens, while its shorter effective focal length means it is slightly less capable for moderate macro work. The STM focus motors are pretty quick and very quiet. On the Sony A5100 (now ten years old) I was using the focus tracking with reasonable success (see above and below). It only has 179 PDAF points, so it's not able to follow small details, but it does a vastly better job than my pro DSLRs or first generation full frame mirrorless cameras do. This €200 camera pairs pretty well with the lens to make an extreme lightweight bargain considering its depth of field and auto focus ability.

 

Stepping up to the three year old Sony ZV-E10 bumps the number of PDAF points up to 425 and enables eye-AF subject detection (human and animal eye-AF), as well as general object tracking. This has been really enjoyable to work with and again the lens feels like it holds up pretty well. The experience here reminds me a lot of that from the original Sony A9, just without the sheer number of PDAF points and not quite as responsive.

Sony ZV-E10 | Red Squirrel | f/1.2, ISO 320

 

Build & Design

I assumed the Sirui 75mm would need to cut a lot of corners in order to get its weight down below 450g (1lb). They have left off weather sealing, switches, custom buttons and an aperture ring to help reduce weight (and costs), but apart from that it's not obvious how they've managed it. The construction feels solid, more so than the Samyang 75mm (although that does have a switch). The design uses a nice mix of materials and looks interesting (plus there are three colour options), although I'm not so keen on the look of the text and large chrome logo.

 

The biggest issue I have with the design is the shape of the lens where it sticks out, near the mount. This does not leave much room for your fingers on the Sony ZV-E10 grip. Sony are also at fault for not having much grip space, but Sirui should have considered this too. There are two quite sharp corners that hit my fingers right on the cuticles and knuckles (see below). This can be downright painful to hold at times, so I really hope that Sirui can address this on a redesign.

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The focus ring grip and turn smoothness feel really good (focus by wire of course). Firmware updates are accessible to everyone through a USB C port on the bottom, which is a nice touch and is a pleasantly simple process. To be honest the only issues I had were with the included lens cap and hood. These could have been better designed as they're quite difficult to get on/off. It's also not flat on the front and thus I can't reliably put the camera down on the lens, is it just me that does that? It feels like it will fall over.