Unlike previous Foveon chips, the Quattro design doesn't attempt to capture full color information at every pixel, instead capturing more spatial resolution than color resolution. This is a fundamentally similar trade-off made by conventional sensors, so it'll be interesting to see whether this latest design can maintain enough of what made Foveon distinctive while trying to offer more competitive results in other respects. Sigma and Foveon continue to claim that this 3-layer approach results in better looking colour images straight out of the camera when compared to a more conventional CCD/CMOS sensor. Whilst this may be true, from the user's point of view the final image is 6192x4128 pixels in size, which limits how big you can print or crop the native image without interpolating it in Adobe Photoshop or another application. With this filter removed, light in the entire infrared spectrum falls on the sensor and with a visible light cut filter on the lens you get infrared-only light on the sensor. Setting the camera to monochrome gives you monochromatic infrared photos on a very high resolution mirrorless camera with interchangeable lenses. The new Sigma sd Quattro H mirrorless camera continues the three core Sigma camera traditions, namely superb image quality at low ISO settings, an idiosyncratic user interface, and frustratingly slow performance. Once again, if you prefer a more leisurely approach to taking pictures, the sd Quattro H will reward you with some amazing images, if you can get on with the "unusual" user interface. But having said that, the SD Quattro’s high ISO performance is still not very good. Below are samples took at various ISO. Left is the full image, and right is the 100% cropped

The camera feels solid like a quality DSLR while having less weight. It feels like a camera that can handle hard work for years to come. Menu control Film makes you think more therefore you actually learn more shooting it. You have to live with the consequences as they are tactile. I shoot digital with the same discipline as film and I am a better photographer for it. I don't see any benefits of digital beside ISO and colour balance over film. These files are 19MP or approximately 5.5K, and no JPEG is recorded in DNG mode unlike the standard RAW+JPEG X3F mode.If nothing else, the use of the full-depth SA lens mount means you can use any of Sigma's impressive Art series of lenses. While it has understandably
not been very prolific with new models, Sigma has maintained a constant, if low-key presence in the camera market. Its current
dp Quattro fixed-lens compacts have a clear, if somewhat niche appeal, with exceptional lenses and superb image quality at low ISOs. The camera we’re considering here, the sd Quattro, uses the same sensor, but with interchangeable lenses. It’s one of a pair of externally identical cameras, with the sd Quattro-H differing in having a larger, higher resolution 25.5-million-pixel sensor with a 1.3x crop. The ‘H’ in ‘sd Quattro H’ represents the sensor size. It is not a full-frame sensor nor is it APS-C, it is in-between. The crop factor is 1.3x, still requiring a 40mm lens to equate to a typical 50mm lens on a full-frame sensor. The Quattro’s sweet spot – image quality People have asked DxO to allow Adobe DNG files, but no. They say, "We understand the issue with this format and here is an explanation: a DNG file cannot be used as just another RAW input file, since it does not contain all the calibration data Optics Pro uses when processing RAW files (especially, but not only, for the denoising algorithm). Therefore, even if Optics Pro could process DNG files without the data it requires, it could not achieve the same quality level as with an original RAW file, and we do not believe people who shoot RAW would be interested in such a substandard solution... This is the reason why Optics Pro only supports the DNG files generated by the cameras we calibrated in our labs..." The Sigma sd Quattro has a very unusual design that's quite unlike any other compact system camera that we've seen before. Measuring 147mm (W) x 95.1mm (H) x 90.8mm (D) and weighing 625grams, it's wide and heavy, with a very pronounced hand-grip with a leatherette covering which helps you to keep a firm hold and accomodates a wide range of hand sizes. There's also a generous thunb-grip at the rear of the camera.

As is usual for mirrorless cameras, both autofocus and metering employ the main imaging sensor. According to Sigma, AF uses a hybrid system with both phase detection and contrast detection on board; users can either select from a nine-point mode, or move the focus area freely across a space roughly 75% of the height and width of the frame. The focus area can also be changed in size in three steps, including a fine point for focusing on a precise part of the scene. Face detection is also available. The Sigma Foveon X3 Quattro CMOS doesn’t just mimic film, the underlying sensor architecture is layered like film emulsion. As well as the innovative sensor which I’ll get to in a moment, the SD Quattro maintains the Sigma DSLR tradition of having a removable IR cut filter. You simply take it out with tweezers. Sigma’s PhotoPro software has come a long way and will create better images for you than simply using the DNG file. Think of it this way; the DNG files are higher quality than the JPEG files, while the X3F files are higher than the DNG. Each step, from JPEG to DNG to X3F, allows for more latitude and control when processing your images.

Sometimes my eyes don’t seem to see straight, so I found the onscreen level to be very handy. It can be turned off for those who don’t want it, but for the rest of us, it’s quite useful. It is the build quality and grip size that sets the SD Quattro apart from the Sony’s and Panasonic’s mirrorless fleet. Even at ISO 400, image degradation is already quite noticeable and the image lost quite a bit of colour information. I wouldn’t want to shoot above ISO 800 normally. I would suggest keep the ISO at 100 or 200 for best image quality. After all, this is really a camera designed for best picture quality over anything else.

That said, landscape shooting does tend to reward a patient approach to picture taking, so neither this need to take extra care, nor the considerable delay as the camera writes its huge DNGs were of particular concern. We suspect most people will be happy enough with the image quality to overcome the occasional hurdle placed in your path. The sd Quattro will preview
your exposure, white balance
and colour mode, giving a good idea of how the image should
turn out before you press the shutter button. Lots of useful extras can be overlaid on the
live-view display, including
gridlines, a dual-axis electronic level display and a live histogram. Indeed, users can configure up to four custom views each for the EVF and LCD, and cycle through them using the display button. On paper, the sd Quattro has a bang up-to-date viewfinder
and screen. Its EVF uses a 2.36-million-dot panel and offers a magnification equivalent to 0.73x. The 3in rear screen has a 1.62-million-dot resolution, although it’s fixed rather than articulated and not touch-sensitive. One nice feature is the addition of a small OLED sub-monitor alongside the LCD that displays key settings such as shutter speed, aperture, metering mode, ISO and exposure mode.

Quattro improvements

The grip is comfortable and makes all-day use easy. While not cupped in like some DSLR cameras, it has enough surface for a solid grip. I don't like at all the Foveon Quattro tech, don't have nothing with the unique in the world exceptional amazing image quality, color appealing, film-like of the previous generations of Foveon, made of three equal layer of red, green and blue. AF speed (in good light at least) is much improved from the Foveon X3 Merrill compact cameras but still nowhere near as fast as a modern mirrorless camera.