Sunday, 2 January 2022

Sigma 12-24mm f/4.5-5-6 DG HSM

Let's have a look at the Sigma 12-24mm f/4.5-5.6 DG HSM, an ultrawide zoom lens that was launched back in 2003. At the time Sigma had a thing for extreme lenses, and for several years afterwards the 12-24mm was the widest zoom lens for 35mm-format cameras and indeed one of the widest lenses of any kind. The only other 12mm lens was the Voigtlander 12mm Heliar, a manual focus lens for Bessa / Leica rangefinders.

Almost twenty years later there are still only a handful of 12mm-or-so ultrawide lenses. I've always been curious about the 12-24mm, but not enough to buy one. However after so long in production they're widely available on the used market so when one popped up on eBay I decided to try it out.

The 12-24mm went through two generations. The original 12-24mm DG HSM was launched in 2003 for all the major camera formats of the day, plus Sigma's own SA mount. DG in Sigma parlance means that the coatings are optimised for digital cameras, and HSM means that it has a silent hypersonic focus motor, akin to Canon's USM.

There was a variation of the generaiton one lens for Pentax and Sony/Minolta cameras, which didn't have HSM, instead relying on the camera's screw drive. The Pentax / Sony-Minolta version had a slightly different physical design, with a manual aperture ring and a painted-on distance scale.

I have the Canon version of the lens. It goes swoosh when it focuses. You can override autofocus by twisting the manual focus ring, which is towards the front of the camera (the inner ring is the zoom control).

The 12-24mm has a bulging front element that produces masses of flare if you shoot towards the sun. There's a small filter holder at the mount end of the lens.

The 12-24mm is a full-frame lens, but it's wide enough to work as an ultrawide zoom for APS-C cameras as well, in which case it becomes a kind of 20-40mm. The lens cap clips into a removable ring that acts as an 82mm filter holder, which is handy if you need to use graduated ND filters. On an APS-C camera you can leave the cap holder in place, but on full-frame it vignettes at all focal lengths wider than 24mm.


This is what happens if you leave the lens cap holder on at 12mm on a full-frame camera. You get a Fax Records album cover.

Physically the 12-24mm comes across as a refinement of Sigma's earlier, massive 15-30mm. Internet reviews grumbled about inconsistent build quality, but the geometry and resolution were praised. The general consensus is that the lens was almost purpose-designed for estate agents, because it's very good at capturing entire rooms and it keeps all the lines nice and straight.

In 2011 Sigma replaced it with the 12-24mm DG HSM II, which had a new body and a slightly different optical design. Judging by the reviews it was sharper but the geometry wasn't as good. In 2017 Sigma launched the 12-24mm f/4 ART, a completely new (and heavier) design with a constant f/4 aperture. By that time the 12-24mm wasn't the widest zoom lens any more, having been beaten in 2015 by the Canon 11-24mm f/4L, which is one wider. And L.

What's the 12-24mm like? On the surface 12mm sounds fantastic, because it's really really wide, but it's also really awkward. You have to make sure that there's something interesting in the top and bottom of the image as well, otherwise you get masses of dirt and sky.

This was shot with the 12-24mm.

It strikes me that it would be a good widescreen video lens, which is something Sigma couldn't have anticipated back in 2003. My hunch is that it would be terrific for hip-hop videos. And porn, although it's not sealed for moisture and I have no idea how the coating would hold up against petroleum-based lubricants.

Back when I was young hip-hop videos were shot with a fisheye lens screwed onto the front of a DV camera, viz the Beastie Boys' "Shake Your Rump", and every porn video consisted of the camera operator moving an ultrawide lens up and down the actors - from a distance of about six centimeters - as they did their thing. Because there are few things more erotic than a close-up of hairless testicles.

Let us move on. As a reportage lens it's simultaneously good - you can get really close to the action - and bad, because the dim aperture makes it hard to focus closely in low light. For landscapes you really need to be in a canyon, or in the mountains, or underneath a fascinating cloud formation.


As mentioned in the text I found 12mm a lot easier to use if I "thought in 16:9", per the following image.

The geometry is excellent. Compare the following two images:



For the second shot I panned the camera up until the horizon was at the bottom of the viewfinder. Note how it's still a flat line, with just a tiny amount of barrel distortion.

I've shot wider, with fisheye lenses. Compare the following two pictures. The one at the top was made with the Sigma lens at 12mm. The one at the bottom was made with an 8mm fisheye lens mounted on an APS-C Fuji S5, corrected - but not fully - with software:


AS you can see the fisheye lens is slightly wider, even though the S5 is an APS-C camera. On a full-frame Canon 5D the result with an 8mm fisheye tests is mind-boggling:

Back to the Sigma lens. Vignetting at f/4.5 is a heck of a thing:

Central resolution at 12mm is excellent, here at f/11, and at f/4.5 it was much the same:

The corners are hard to judge because of the stretching, but they don't improve much when stopped down (f/11 at the top, f/4.5 below, corrected for brightness):


My copy seemed to be less sharp on the left side than the right. The corners aren't an issue if you're shooting video at 16:9 or indeed if you crop the image to a wider aspect ratio. The performance of my copy at 24mm is essentially the same, again with a blurrier left side. I found the viewfinder uncomfortably dim at f/5.6. Some Sigma lenses of this vintage had a slight yellow colour cast, but looking at the images I shot I can't convince myself that I see it.

I'm not sure if it was the time of year, or the lack of cruise liners, or the weather, but the air was unusually clear in Venice. I could see the foothills of the Dolomites, about forty miles away:

If I had brought along a super-telephoto and stood on the Lido I could have taken some shots of the Basilica with mountains in the background, but I didn't, so I didn't.


This is a "majlis" made of bamboo.

Do I have anything else to say about the 12-24mm? It's simultaneously extraordinary and slightly boring. After a while everything I shot resembled a Doom level, with perfect geometry and everything in focus. Which is nice, but it gets monotonous. With the aperture wide open there's a lot of vignetting, but even though the lens doesn't have any kind of image stabilisation it's easy to shoot at slower speeds, so I kept mine at f/8 almost all of the time.

As a video lens the bulbous front element prevents the use of a graduated ND filter, although this isn't a huge problem if you shoot landscape stills, because you can bracket. Back in 2003 it was one of a handful of lenses that had ultrawide coverage with APS-C cameras, but almost twenty years later there are smaller, faster options if you intended to shoot APS-C.

Still, on a full-frame camera it's an excellent way to get "proper" ultrawide coverage without using software correction or panorama stitching, and as mentioned passim the geometry requires essentially no work in Photoshop, so if you need to shoot a mass of interiors you can go bang-bang-bang until the flash burns out. My copy also had essentially no CA, which is odd because some reviews point out that it has lots; perhaps I was lucky to have a well-aligned sample.

Friday, 24 December 2021

Alesis Micro Gate: Bring Her Not Forth

Let's have a quick look at the Alesis Micro Gate, or MICRO GATE as the manual calls it. It's a compact effects box from 1988, the tail end of the Physical Age, before everything and everybody ascended to The Cloud.

The Micro Gate was part of Alesis' compact, budget-priced MICRO SERIES. I don't have access to any sales figures, but judging by eBay listings the two MicroVerbs sold like hot cakes, the Micro Limiter compressor less so, the others not so much.

As of 2021 they're all totally obsolete, the Micro Gate doubly so because it's a humble noise gate. It turns off the volume when the incoming signal falls below a certain threshold. Noise gates are often used by guitarists to get rid of mains hum and clicking noises, but they're also useful as a way of imposing a volume envelope on arbitrary sounds, e.g. they make things sound stuttery. In this video I use the Micro Gate to make a drum loop more interesting, by chopping bits out of it in real time:


When it was new the Micro Gate at the home studio market; the kind of musician who might have an Atari ST and an Akai S-something sampler. For the most part the used market for synthesisers and analogue effects has been mined out - eBay prices are famously over-the-top - but there's a rich seam of affordable digital rackmount effects and 16-bit studio gear from the 1990s that can still be found cheaply.

For good reason, too, because digital effects units from the 1990s generally didn't have any special magic about them. Computer plugins have replaced them all. Objectively the Micro Gate doesn't make a lot of sense in the modern age, but I was curious about it and found one going cheap, in very good condition, so I decided to build up my collection of Alesis effects.

The Micro, Nano, Pico etc effects had a standard back-panel layout, with unbalanced 1/4" sockets plus a TRS control socket. They all used uncommon 9v AC power supplies.

The Micro series was launched in 1986 with the MICROVERB, a 16-bit stereo reverb with sixteen non-editable presets. It was housed in a 1/3rd-of-a-rack-sized case that could be screwed into a metal plate for rackmounting. In 1988 Alesis continued the series with the MICRO GATE, MICRO LIMITER, and the MICRO ENHANCER, a exciter.

The company also replaced the original MicroVerb with the MICROVERB II, which was similar but with greater bandwidth and slightly different presets. I have one! It would have benefited from EQ, because it has a very bright sound, but it's surprisingly decent for a budget reverb from the late 1980s.

There was also the MICRO CUE AMP, a headphone amplifier. Overall it's a peculiar range. You'd think Alesis would have thrown in a delay or chorus, but no. In the 1990s Alesis continued to make third-of-a-rack effects under the NANO and PICO names, although confusingly the later MicroVerbs were housed in full-sized 19" racks, so they weren't micro any more.

As you can see the later NanoCompressor is less deep than the Micro effects. Perhaps it has a smaller PCB.

What's the Micro Gate like? It's very simple. The threshold control sets the level at which the gate cuts out the sound. The delay knob controls how long the gate stays open - it's a bit like the ON knob on a VCS3 synthesiser - and the rate knob controls the speed at which the gate closes. With the delay knob counterclockwise and the rate knob clockwise the effect is jarring, with the knobs turned the other way the result is smooth.

Now, it's worth pointing out that noise gates only turn off the volume. They don't do Dolby-style noise reduction; you can't use them to remove hiss from a signal. You can only turn off the signal during the quiet bits. Even in 2021 real-time noise reduction is difficult and the results are usually unimpressive.

By itself the Micro Gate is a bit dull, but it becomes interesting when you plug something into the trigger input. The trigger input activates the gate when it detects an incoming signal. In the video above I use a kick drum pattern from a Korg Volca Beats drum machine to trigger the gate. The result is a kind of synchronised tremolo effect that sounds awesome if you feed a large, sustained chord with masses of reverb into it.

The effect was used a lot in dance music in the 1990s. The first example that springs to mind is Olive's "You're Not Alone", where the very first sound in this video is a chord sequenced played through a noise gate that isn't quite on the beat:


That's a particularly good example. The effect can be achieved in several different ways, but the strings in "Alone" are chopped without any change in tone, in such a way that the sustain tail of the preceding notes bleeds into the notes that follow it. The notes don't have an obvious attack phase. It's hard to describe in words.

The same effect pops up in Paul Oakenfold's "Southern Sun" and probably lots of other records, although it's hard to find an example that's unquivocally made with a noise gate, and not side chain compression or an arpeggio triggering a strings sample.

You know, I've just spent the last fifteen minutes listening to late 1990s trance on YouTube. There's something heartbreaking about late 1990s trance. Not just because they dreamed of a happier future than the one we got. Behind the maximalist production and slick videos there's an underlying sadness to trance music, because the weekend will soon be over.

Trance music is a scream of defiance directed at the unstoppable force of entropy. Death will claim us all, but not tonight. Not tonight.