Camera Reviews / Sigma Cameras i Now Shooting!

19.61 Megapixels	Sigma SA bayonet	APS-C size sensor

Sigma sd Quattro Review -- Now Shooting!

by Jeremy Gray and William Brawley
Preview posted: 02/23/2016

Updates:
10/13/2016: Field Test posted!

Sigma continues to forge ahead in their own unique style with their first mirrorless interchangeable lens camera. In classic Sigma fashion, the new sd Quattro sports an APS-C sized Foveon X3 sensor and strikingly unconventional design. Writer and photographer Jeremy Gray brought this camera along not only into is own backyard in Maine but also on a recent trip to Peru. According to his detailed Field Test, the Sigma sd Quattro proves to be a strange camera, one with a lot of quirks and problems, but one that manages to capture excellent images if you keep in mind this camera's shortcomings. Read on to find out how this camera handles out in the field and if you can deal with this camera's limitations.

For those looking for our detailed overview of the camera's features and specs, please click here.

 

Sigma sd Quattro Field Test

Foveon-powered Quattro offers excellent image quality but a number of quirks

by Jeremy Gray | 10/13/2016

Sigma 18-35mm f/1.8 DC HSM Art lens at 24mm (36mm equivalent), f/8, 1s, ISO 100, +0.3 EV Click for full-size image.

Sigma sd Quattro: an interesting, niche camera both inside and out

While Sigma's optical offerings continue to earn fans for their high-quality designs and performance, the Japanese company's cameras have always been a bit more niche. Not that this is a bad thing, but their cameras have tended toward the unusual. Their first interchangeable lens mirrorless camera is no exception. The Sigma sd Quattro (and sd Quattro H) is an interesting camera, both from a design standpoint and a features standpoint.

Note: Before you spend time looking for the usual video and wireless features sections that I typically include in my Field Tests, I'll save you the scrolling, they don't exist. Unlike almost every other camera that hits the market -- at least ones that are marketed to enthusiasts -- the Sigma sd Quattro does not include either video recording capabilities or wireless functionality. More on this later.

Key Features

• 19.6-megapixel APS-C Foveon X3 Quattro CMOS sensor
• ISO 100-6400
• 2.36M-dot electronic viewfinder with 100% coverage
• 3-inch rear display and sub-display
• 9-point hybrid autofocus system
• 3.6 frames per second continuous RAW shooting
• US$800 price for the body only

Distinct camera body handles okay, but it includes a few questionable design decisions

Polarizing. That's probably the best way I can describe the styling of the Sigma sd Quattro. Personally, I like it a lot. In a sea of general sameness, the sd Quattro stands out. With that said, I can understand how someone might look at it and proclaim it to be "ugly" or "hideous." What I think everyone can agree on, at least, is that the camera is distinct in its appearance.

Now that we have addressed the elephant in the room that is the Sigma sd Quattro's appearance, how does it actually feel to hold and use? It's okay, but not great. The front grip is quite large, but when paired with a fairly heavy lens such as the Sigma 18-35mm f/1.8 DC lens I used, it doesn't offer quite enough grip for me to feel comfortable holding the camera with just one hand while trying to operate the command dial on the top deck of the camera. One of the issues is that the thumb grip on the rear of the camera ended up blocking my thumb from being able to rotate the dial. Another aspect of the camera's design that I don't like is that the AF selection button is not only small, but it's very low on the camera's back. If it were within reach of your right thumb, I think that would be much better.

Despite being a mirrorless camera with an APS-C sensor, the sd Quattro is quite large and heavy. This is not a compact mirrorless camera by any stretch of the imagination. Yet, there's a lot of empty space on the camera. Functions that have been relegated to a 'quick start' menu, such as white balance or drive mode, could have easily been fit on the camera body itself. There's something to be sad about not putting too many controls on a camera, but the sd Quattro goes too far the other direction and feels somewhat bare bones. The body weighs 22 ounces and has dimensions of 5.8 x 3.7 x 3.6 inches. When paired with a lens like the 18-35mm f/1.8, it's a large and heavy combination.

Ultimately, it wasn't the camera's unusual appearance that I didn't care for, it was some odd button placement and just a general lack of refinement in the ergonomics. With that said, perhaps others will love the feel of the camera and the button placement on the sd Quattro even though I didn't.

Sigma sd Quattro is all about the Foveon X3 sensor

The primary reason you would consider purchasing the Sigma sd Quattro is its Foveon image sensor. This unique sensor delivers excellent results, albeit across a limited range of situations and with some severe drawbacks. The Foveon X3 sensor found in the Sigma sd Quattro is a 19.61-megapixel APS-C sensor, although it is said to deliver results similar results as a 39-megapixel Bayer-pattern sensor thanks to its unique design.

Unlike a Bayer-pattern sensor, the Foveon sensor captures full RGB data with each pixel due to its layered design. The top layer has approximately 20 megapixels of resolution with the middle and bottom layer resolves just under 5 megapixels. The top layer of the sensor records blue color and luminance, the middle layer deals with green and finally the bottom layer handles red.

While the Foveon sensor results in much more data being captured by each pixel (three colors versus just one), that also means that the camera has to process a lot more data than a camera with a standard Bayer sensor has to. Unfortunately, despite the sd Quattro employing what is actually fast processing, this means that the camera is quite slow.

Due to its Foveon X3 "direct image sensor" -- a sensor that captures all three RGB colors at each photo-site -- the Sigma sd Quattro produces images with much more fine detail than an equivalent-megapixel Bayer-pattern sensor. If you want to learn much more about the Foveon X3 sensor, and how to characterize its resolution, you should read this Q&A we did in 2014.

To summarize, the benefits of a Foveon sensor are that you capture much more data in each pixel and therefore achieve resolution equivalent to a much higher megapixel Bayer-pattern sensor without needing to cram as many pixels on the sensor, thereby improving signal-to-noise performance. The negatives are that the camera has to perform much more extensive processing.

Sigma 18-35mm f/1.8 DC HSM Art lens at 35mm (52mm equivalent), f/4, 1/250s, ISO 100 This image has been modified. Click for full-size image.

Image Quality: Foveon sensor delivers great detail, with a catch...

The Sigma sd Quattro is the first Foveon sensor camera I've used. After coming to grips with a few of the camera's quirks, I came to realize that it offers something very few other cameras can, especially at $800: fantastic detail and sharpness. The first time I looked at an image from the sd Quattro at 100% I was blown away by the level of fine detail and crispness in the photo.

Sigma 18-35mm f/1.8 DC HSM Art lens at 18mm (27mm equivalent), f/1.8, 1/2500s, ISO 100 This image has been modified. Click for full-size image.

It is not without its faults, however, as it has some strange tendencies with regards to certain colors. Reds, in particular, proved problematic. In scenes where every other color was well-represented, reds, such as in fall foliage, took on an unpleasant magenta hue and in some cases were clipped entirely with too much saturation. This issue was not particularly easy to address in post-processing either.

...the catch? High ISO performance is disappointing.

While image quality is generally excellent at base ISO, the Sigma sd Quattro produces poor images at higher ISO settings. Even at ISO 800, fine details are mushy, colors are inaccurate and there's considerable noise present in the image.

When considering JPEG images straight from the camera, the situation is pretty dire at ISO 800 and above. There is noticeable banding as well as small black pixels scattered throughout images at ISO 800. Colors become muted, with the exception of reds, which become more saturated. Even at ISO 400 there are problems, as there is some color noise visible in images when viewed at full size.

Sigma sd Quattro Noise Comparison 100% Center Crops from JPEG images (Click for full-size images)
ISO 100 Full Scene
ISO 100	ISO 200
ISO 400	ISO 800
ISO 1600	ISO 3200
ISO 6400

ISO 1600, which is typically a very usable ISO speed in modern APS-C cameras, is very bad with the sd Quattro. The sharpness that the sd Quattro features, its primary image quality component that sets it apart from the competition, is absent at higher ISOs. In addition to softness, there is banding and poor color representation. ISO 3200 and 6400, forget about them, as far as I'm concerned they're completely useless.

The situation with RAW files is even poorer, although you do have a bit more flexibility in how you address noise. There is just far too much noise at higher ISOs (1600 and above) to even begin to deal with in Sigma's Photo Pro software (the best way to handle the camera's .X3F files, although not an elegant solution, as I will discuss later).

Frankly, if I was using the Sigma sd Quattro for my own work, I would never use it past base ISO. The primary reason to use this camera is its sharpness and fine detail and that begins to be lost even at ISO 200 and is completely gone by ISO 1600.

Sigma 18-35mm f/1.8 DC HSM Art lens at 20mm (30mm equivalent), f/1.8, 15s, ISO 1600 Click for full-size image.

Super Fine Detail mode: Detail is good, but the scene has to be perfectly still

I was excited to try out the sd Quattro's Super Fine Detail (SFD) mode, but it has numerous drawbacks that limit its real-world usability. The way that the mode works is that the camera captures seven frames at different exposures and combines them in-camera into an .X3I raw file (which you cannot preview in-camera) to produce a final image -- when processed in Sigma's software -- that has improved dynamic range and less noise than a single image.

Sigma 18-35mm f/1.8 DC HSM Art lens at 31mm (46mm equivalent), f/8, -0.7 EV, SFD mode. This Super Fine Detail image has been processed from a raw file and edited. Click the image for the full-size processed JPEG file.

You need an absolutely still subject or scene for SFD mode to work well at all. In the above image, which was a mostly still scene, parts of the image is very sharp while other parts show strange artifacts, which you can see below. I think you're better off skipping SFD mode in most cases and processing/stacking regular RAW images from the sd Quattro.

100% crop of the above image

100% crop of the above image

Sigma sd Quattro user experience leaves a lot to be desired

My first experiences with the Sigma sd Quattro were in Peru while I was on vacation. Regrettably, this testing ground regularly showcased the camera's weaknesses. Without a tripod, the sd Quattro is limited unless you're shooting at wide apertures. As I discussed above, pushing the ISO even to 400 greatly reduces the inherent resolution benefits of the Foveon sensor. So as a travel camera, which was how I was using the camera, I found it to be a less than friendly companion.

Sigma 18-35mm f/1.8 DC HSM Art lens at 35mm (52mm equivalent), f/2.8, 1/160s, ISO 100, -0.7 EV. This image has been cropped. Click for full-size image.

Its controls, while fine when you have the time to slow down, do just that, slow you down. The autofocus system is not particularly user-friendly and manually focusing, in general, is not ideal without the ability to take your time and set up. Exposure and white balance metering was good, but the camera is so slow to process a single image that checking your resulting shot takes a frustratingly long time.

Viewfinder is not good at all, but the rear display and sub-display are nice

The sd Quattro features a 2,360K-dot electronic viewfinder. It has 100% coverage and a 35mm-equivalent magnification ratio of around 0.73x. It certainly doesn't want for sharpness, although its performance isn't all that impressive. The live view image is very choppy at times, and it simply doesn't offer a smooth view of your subject. I found that the EVF's built-in proximity sensor to switch between it and the rear display worked quite well though.

Sigma 18-35mm f/1.8 DC HSM Art lens at 20mm (30mm equivalent), f/1.8, 15s, ISO 1600 Click for full-size image.

Speaking of the rear display, the 3-inch screen has 1,620,000 dots and provides a nice, sharp image. Unfortunately, the display doesn't tilt or offer any touchscreen functionality at all, which is very disappointing. On a more positive note, the interesting sub-display next to the 3-inch rear display is a cool idea and a nice proxy for the top display you sometimes find on cameras.

The sub-display shows remaining images, shutter speed, aperture, battery life, exposure compensation, ISO, metering mode and shooting mode as white text on a black background, which is easy to read in any lighting condition. Along the right side of the display are corresponding buttons for exposure compensation, ISO, metering and shooting mode along with a button to turn the smaller display off entirely (although I never felt tempted to do that). When you press one of the buttons only the setting you're changing stays illuminated on the display, making it easy to see what you're doing. The sub display is an excellent alternative to a top display and I like its implementation a lot. It allows you to keep your live view image clean and uncluttered.

Metering is inconsistent and unreliable

The sd Quattro's metering performance is not stellar as I found that it has a tendency to clip highlights without the use of any exposure compensation. I regularly opted for -0.3 and -0.7 exposure compensation, although compensation is available up to +/-5.0 EVs. Metering modes include evaluative, center-weighted and average metering modes, and they can be quickly changed with the dedicated metering button next to the sub display. The sd Quattro also includes 3 or 5-shot auto bracketing.

White balance metering performance was quite good when using auto white balance, and I didn't have any issues with it, but you can also select auto (lighting source priority), daylight, shade, overcast, incandescent, fluorescent, flash and color temperature (K) in addition to three custom white balance slots.

Sigma 18-35mm f/1.8 DC HSM Art lens at 35mm (52mm equivalent), f/4, 1/60s, ISO 100 This image has been modified. Click for full-size image.

Sigma 18-35mm f/1.8 DC HSM Art lens at 35mm (52mm equivalent), f/4, 1/60s, ISO 100 This image shows a very common occurrence with the Sigma sd Quattro: clipped highlights. If it was just a small area of the image, I'd understand, but there are highlights across much of the image. Click for full-size image.

Sluggish autofocus is severely limiting in real-world scenarios

With its hybrid autofocus system, you might expect autofocus performance to be one of the sd Quattro's highlights, but that was not my experience with the camera. My biggest issue with the autofocus system is that it has only nine AF points to choose from. You can toggle between selecting from the nine points or moving the AF area across the frame with much finer control, but this is very slow. Not only are there not all that many autofocus points, but they don't densely cover the frame nor extend very near to the edge.

Sigma 18-35mm f/1.8 DC HSM Art lens at 35mm (52mm equivalent), f/2.5, 1/500s, ISO 100 This image has been modified. Click for full-size image.

Without a touchscreen and with the AF selection button all the way at the bottom of the camera's back, moving the AF point is slow. The four directional buttons on the back of the camera don't serve much purpose by default while shooting, so they really should be assigned right off the bat to quickly move the AF point without any fussing about with a separate AF selection button.

It isn't just selecting an AF point that is slow, but also the autofocus system itself. Focus hunting was a regular occurrence during my time with the sd Quattro, even when shooting in high-contrast, brightly-lit situations.

The sd Quattro is the first camera I can recall using that didn't offer any sort of fully automatic focusing mode. There's face detect AF that will automatically focus on faces in the frame – which worked pretty well in my experience – but other than that, you have to manually select a single AF point. There's no focusing mode that allows you to just point and shoot the camera.

Sigma 18-35mm f/1.8 DC HSM Art lens at 35mm (52mm equivalent), f/1.8, 1/3200s, ISO 320 This image has been modified. Click for full-size image.

Continuous autofocus is not particularly useful for a couple reasons. The sd Quattro is slow and is not designed for continuous shooting, so the utility of continuous autofocus is questionable from the start. And as it turns out, the camera can't keep up with moving subjects well at all, and it consistently hunts for focus.

If you're going to get the most out of the sd Quattro, your subjects need to be stationary. Not only that, but you need to be able to take your time and ensure that focus is perfect. When everything comes together, images are very sharp. It's unfortunate then that in many real-world scenarios, the camera is unable to deliver the image results it's capable of, in large part due to a sluggish focusing system.

Performance is a problem for the very slow sd Quattro

I haven't had a lot of positive things to say about the sd Quattro thus far and unfortunately I've come to the section where I found that the camera struggles the most…performance. When shooting RAW images, the sd Quattro is very slow. When capturing an image, you have to wait a considerable amount of time before being able to view it in playback. There were many times when I captured an image and wanted to look at it, but the camera took so long to register my press of the "playback" button that I was concerned that the body had locked up. The situation is only slightly better when shooting JPEG images, but not significantly.

Continuous shooting performance is pretty underwhelming too, shooting RAW images at up to 3.6 frames per second for 14 frames. During my testing, clearing the buffer took nearly 45 seconds although I also only was able to record a dozen frames rather than 14. When shooting JPEG images, the buffer clears slightly faster but that was the only difference.

Sigma 18-35mm f/1.8 DC HSM Art lens at 35mm (52mm equivalent), f/9, 1/160s, ISO 100 This boat was not moving fast, but it was moving fast enough to be an issue for the sd Quattro. I wasn't able to capture many shots before it was gone. Click for full-size image.

Battery life will vary depending on how you use the sd Quattro, as is the case with any camera, but my experience with the sd Quattro's battery life was rather disappointing. It is rated for 200 shots, and I was achieving results a bit less than that. Granted, I was checking the monitor and playing with menus frequently, but that's not very impressive. If you're going to be out with the sd Quattro, you'll want a spare battery. The sd Quattro, unlike earlier fixed-lens Sigma cameras like the dp2 Quattro, ships with only a single lithium-ion battery pack rather than two.

As was the case with autofocus, the sd Quattro simply feels sluggish. It felt like I was consistently fighting against the camera. Performance is not the sd Quattro's strong suit. With that said, this isn't a camera that is trying to be a speed demon nor is it claiming to be ideal for fast-paced shooting such as sports or wildlife. I don't want to beat up on the Sigma too much for its slow performance as it is severely handicapped in this department by its unique Foveon sensor, which as I mentioned above produces incredible image quality in certain situations.

Sigma Photo Pro software: A necessary evil

You can't discuss a Sigma camera without mentioning how difficult it is to process RAW files from a Foveon sensor. The sensor is unique and there aren't many good ways to process the files. Adobe doesn't support RAW files from Sigma cameras, for example. What you instead have to do is download and install the free Sigma Photo Pro software. Once you've downloaded it, you might think that the process will now be quick and easy. It won't be.

Sigma Photo Pro is one of the slowest pieces of software I've used, and it routinely crashed on my computer. It might work perfectly well for you, but for me it was a struggle. The user interface is convoluted and processing files takes a considerable amount of time (and my Mac is not a slow machine). I was able to achieve pretty good results, however. Ultimately, the Sigma sd Quattro has proven to be slow from capture all the way to final image processing. And yet, the frustrations diminished when I looked at the sharp, detailed final images.

Sigma sd Quattro: A camera of compromises and omissions

As I mentioned in the introduction to this field test, the Sigma sd Quattro does not offer any video recording or wireless functionality. The former omission is due to the Foveon sensor, and its data output speed. With the stacked design of the Foveon sensor, the camera reads out a lot more data than a standard sensor design. This high level of data means that the camera simply cannot process the video data fast enough to offer good video performance without sacrificing in other regards. You can read more about the technology and Sigma's reason for opting not to include video in the sd Quattro (or any of their other Foveon cameras) here.

While there is a perfectly good reason for not including video recording in the sd Quattro, the fact remains that in the current camera market, the sd Quattro stands out for its omission. As for why there's no wireless functionality, I can't think of any technological reason for not including that similarly common feature.

Sigma 18-35mm f/1.8 DC HSM Art lens at 32mm (48mm equivalent), f/8, 1/50s, ISO 100, -0.3 EV. This image has been modified. Click for full-size image.

Sigma sd Quattro Field Test Summary

The Sigma sd Quattro is frustrating, but still very appealing in certain situations

What I like:

• Image quality at low ISOs is very good
• Low ISO images incredibly sharp and detailed
• Rear sub display works very well and is a cool idea

What I dislike:

• Lack of a touchscreen is disappointing
• Overall physical design is not very user-friendly
• No video recording capabilities. (Note: This omission is not unique to this model, but rather all Foveon cameras. Nonetheless, not being able to record video is notable in the current marketplace.)
• No wireless functionality
• Autofocus performance is poor
• Continuous shooting speeds are disappointingly slow
• Shot-to-shot cycling is very slow

Sigma 18-35mm f/1.8 DC HSM Art lens at 20mm (30mm equivalent), f/4, 1/250s, ISO 100, -0.3 EV This image has been modified. Click for full-size image.

Taking a look at the two lists above, you'll notice that the "What I don't like" list is rather long and includes numerous missing features and otherwise poor performance results. Does that mean that the camera is bad? That depends on what you expect a camera to do. If your sole, or at least primary, focus is capturing high-quality still images of stationary subjects at low ISOs, then the sd Quattro is an excellent camera. In fact, it is not only excellent, it is probably the best you can get for under US$1,000.

But what if you like to shoot moving subjects, shoot in low light, record video or use a touchscreen? Then this camera really isn't for you. In a world where so many cameras try to be a jack-of-all-trades and end up very much masters of none, the admittedly limited Sigma sd Quattro is actually a breath of fresh air in a way. It doesn't attempt to do everything, but it does a few things extremely well. One of those things is capturing high quality images. For some photographers, image quality trumps all else.

Sigma 18-35mm f/1.8 DC HSM Art lens at 22mm (33mm equivalent), f/8, 1s, ISO 100, -0.7 EV This image has been modified. Click for full-size image.

The Foveon sensor at the core of the Sigma sd Quattro is special. It presents both pros and cons that set it apart from every non-Sigma camera on the market. Its base ISO image quality and resolving power are hugely impressive. But this capability comes at the cost of speed and high ISO capabilities as well as the ability to record video. Ultimately, I find it hard to recommend the sd Quattro for anything other than tripod-based, low ISO photography. Of course, if that's what you shoot and image quality is your sole concern, then I'd be hard-pressed to recommend anything else.

 

 

Sigma sd Quattro Review -- Overview

by Jeremy Gray and William Brawley
Preview posted: 02/23/2016

Sigma is taking their Quattro line of Foveon-based cameras in a new direction with the introduction of the new Sigma sd Quattro -- their first mirrorless interchangeable lens camera. In fact, there's a pair of new "sd Quattro" mirrorless cameras. Sharing a wholly similar body design and SA lens mount, the "standard" Sigma sd Quattro mirrorless camera packs an APS-C sized sensor, while the Sigma sd Quattro H sports a larger APS-H sized Foveon X3 sensor. Designed for photographers who demand high image quality, portability, and the flexibility of interchangeable lenses, the sd Quattro aims to continue Sigma's "history of innovation," according to Sigma Corporation of America's president Mark Amir-Hamzeh.

Beginning with the design, the Sigma sd Quattro's body has a very distinct shape. Radically different than the earlier and equally-striking design of the dp Quattro fixed-lens cameras, it's nevertheless clear that Sigma isn't shy about using unconventional camera designs. The splash- and dust-proof design, in addition to magnesium alloy construction, give the camera a durable body. The control layout, while slightly different than on a "typical" camera, is more or less straightforward with the usual array of buttons and controls you expect to find.

On the back is a 3-inch 1.62M-dot LCD monitor, a 2.36M-dot LCD electronic viewfinder, and a variety of controls. The display does not tilt nor does it have touchscreen capabilities, though. However, the Sigma sd Quattro does have an interesting sub-monitor to the right of its 3-inch display. The sub-monitor displays information such as remaining shots, shutter speed, aperture, ISO, exposure compensation, and more. Thus, critical shooting information is quickly available to the user in the absence of a top display. The two displays have also both been designed with a sheet of anti-reflective material between the LCDs and the protective glass covering to help combat glare and reflections in bright conditions.

The electronic viewfinder has 1.10x magnification (0.73x in 35mm format), approximately 100% coverage, 21mm eyepoint and -4 to +2 diopter adjustment. There is a toggle switch next to the viewfinder to switch between the viewfinder or display, but there is also an auto mode that utilizes a sensor to automatically switch between the viewfinder and display depending on your usage.

The back of the Sigma sd Quattro includes a 3-inch LCD, separate status LCD, 2.36M-dot LCD EVF, and a wide array of controls.

With an APS-C "19.6-megapixel" Foveon Direct Imaging CMOS sensor, Sigma claims the sd Quattro captures image quality similar to what you would achieve using a 39-megapixel Bayer-pattern sensor. Here at IR, we won't go so far as to say it's equivalent to a 39-megapixel Bayer senor, but it certainly should be better than a conventional 19.6-megapixel sensor, at least at low ISOs -- especially when it comes to color resolution.

The asymmetrical stacked sensor captures detail and blue channel information on its top 19.6-megapixel layer and captures red and green color information using two 4.9-megapixel layers below. This sensor design negates the need for an optical low pass filter, which helps with fine detail resolving power.

For more on how the Foveon X3 Quattro sensor works, see our in-depth Sigma dp2 Quattro review.

The Sigma sd Quattro also includes the newest Dual TRUE III image processor which is designed to take full advantage of the stacked sensor as well as Sigma's extensive line of SA-mount lenses. Photographers can utilize their equipment to the highest extent by shooting in 14-bit lossless compressed RAW (.X3F) image format, which can be processed using Sigma's Photo Pro software.

Two RAW image sizes are offered: High, which captures the full resolution offered at all three layers, and Low which captures the blue layer at the same resolution as the red and green layers (4.9 megapixels).

The Sigma sd Quattro also utilizes DDR3 DRAM for buffer memory, with about twice the capacity as found in the dp Quattro series of cameras. This allows the sd Quattro to capture 14 RAW frames in a burst at up to 3.6 frames per second according to the company. And if you're willing to shoot at the reduced "Low" resolution of about 4.9 megapixels, the claimed burst performance increases to 28 images at 5.1 frames per second.

The Sigma sd Quattro also includes two-mode autofocus detection which utilizes phase-detection autofocus for focusing speed and contrast-detection autofocus for focusing accuracy. Operating range is specified at EV -1 to EV 18 (ISO 100/F1.4). The addition of phase-detection AF over the contrast-detect-only AF of the dp series should help maximize focusing performance with existing SA-mount lenses that are not optimized for contrast-detect AF. Enhanced autofocus modes include movement prediction, face detection, and free movement. When using free movement, you can select from 9 autofocus points and adjust the size of the AF point. A focus assist light is provided for low-light conditions. When manually focusing, you can utilize focus peaking to provide a colored outline around the currently in-focus subject. The available color choices are white, black, red, and yellow.

Notice the deep flange-back distance of the lens mount required to be compatible with existing SA-mount lenses. Here, you can also see the "lock" switch on the top of the body. This switch allows the user to "lock" the buttons on the camera and prevent accidental changes to settings while shooting. Which buttons are locked is user-customizable.

In addition to enhanced autofocus, Sigma also says that the sd Quattro's Auto White Balance algorithm has been updated to provide better accuracy.

As do most cameras these days, the Sigma sd Quattro offers a number of aspect ratios for its images in addition to its native 3:2 aspect ratio. These include the familiar 16:9, 4:3 and 1:1 ratios, but unusually, 21:9 and 7:6 are also offered. The Sigma sd Quattro doesn't provide any scene modes, but color modes on offer are Standard, Vivid, Neutral, Portrait, Landscape, Cinema, Sunset Red, Forest Green, FOV Classic Blue, FOV Classic Yellow, and Monochrome.

In addition to Sigma's interpolated "Super High" resolution mode producing 39-megapixel (7,680 x 5,120) JPEG images, the sd Quattro offers a new "Super-Fine Detail" mode designed to bring out the sensor's full potential. This mode captures seven separate exposures and merges them into one image with improved dynamic range and lower noise, although any individual frame can be extracted as well from the new .X3I RAW file format.

The Sigma sd Quattro has a native ISO sensitivity range of 100-6400 and includes a programmable Auto ISO mode. Shutter speeds range from 30 seconds to 1/4000s and includes a bulb mode for longer exposures of up to two minutes.

The Sigma sd Quattro does not have a built-in flash, but it does have a hot shoe over the lens mount's central axis, as well as a PC-socket on the front. The camera's maximum flash sync speed is 1/180s. Exposure metering modes include evaluative, center-weighted, and spot, and +/- 5.0EV exposure compensation is available in 0.3EV increments. Continuing in the footsteps of the SD1 DSLR and dp Quattro-series, the sd Quattro cannot capture video -- this is purely a stills camera.

As far as connectivity is concerned, the Sigma sd Quattro has a Mini HDMI (Type C) port, a USB 3.0 Super Speed data port, and a wired remote control jack. The Sigma sd Quattro utilizes SD/SDHC/SDXC memory for storage using a single card slot, however we don't yet know if faster UHS-I types are supported.

Power is supplied from a proprietary BP-61 lithium-ion battery back, however battery life has not been published as of this writing. But because of the complex processing involved in separating the color response of each layer, battery life hasn't been great from Foveon-based Sigma cameras in the past. (The Sigma dp2 Quattro for instance had a battery life of only 200 shots per charge without a flash, so Sigma included a second battery in the bundle.) The good news for the sd Quattro is there is an optional PG-41 Power Grip which holds up to two additional batteries, which should triple battery life over a single battery in the body. As you'd expect, the weatherproofed vertical grip also provides redundant controls such as an On/Off button, two command dials, an AF/AEL button and a programmable FUNC button.

Though quirky and not without their issues, Sigma's earlier DP Merrill- and dp Quattro-series fixed lens cameras with Foveon sensors were still capable of capturing some excellent images at low ISOs, so it will interesting to see how these new Sigma mirrorless models fare once we get them in for testing.

The Sigma sd Quattro mirrorless camera began shipping in the fall of 2016, with a street price of about US$800 body-only, or kitted with the Sigma 30mm f/1.4 Art lens for about US$1,000.