Using your camera’s monochrome mode has several advantages. You can use the camera’s built-in filters (including the old black-and-white standbys red, yellow and green), you can view the image in monochrome on the LCD monitor, and if you shoot RAW rather than JPEG, you have the ability to process the resulting file into monochrome or full color after the fact. The primary drawback is that conventional digital sensors, with their Bayer RGB filter arrays, don’t provide optimal monochrome image quality—more on this in a bit.
Converting a color image into monochrome in your computer offers the advantages of lots of control—your home computer is more powerful than the one built into your camera, and can handle more complex algorithms, and specialized monochrome software such as Nik Silver Efex Pro provides powerful conversion and finishing tools. And you can convert any digital image, whether it was shot recently or it’s a scan from an old Kodachrome transparency. Photoshop’s Channel Mixer gives you tremendous control over the tones in the image. (See “Monochrome Conversion” by Ming Thein in this issue for more about using the Channel Mixer.) The main drawback to converting a color image is the same as with using the camera’s monochrome mode: That color original image suffers the effects of demosaicing.
Why Monochrome Cameras Do It Better
Conventional image sensors consist of a fine grid of millions of pixels or photodiodes that record light in proportion to its intensity. Each pixel can detect how much light strikes it, but not what color that light is. To provide color information, most manufacturers position a grid of primary-colored filters called a Bayer array (named after the Kodak scientist who devised it) over the pixels, with one primary color, red, green or blue, covering each pixel so that each pixel receives only light of that color. Then, through a process known as demosaicing, the camera’s processor (if you shoot JPEG) or your RAW converter (if you shoot RAW) creates a full-color image, using color data from neighboring pixels and interpolation via complex proprietary algorithms to furnish the missing color data for each pixel.
This process works quite well—all major-brand digital cameras except Sigma’s use this method on amateur as well as pro-oriented models (see the “Sigma/Foveon” sidebar). However, the demosaicing process does have some drawbacks. First, a lot of light is wasted, since the colored filters block two-thirds of the light from reaching each pixel. Second, the demosaicing process produces aliasing—moiré, color artifacts and the like. To combat this, most sensors also include an anti-aliasing (AA) filter, or optical low-pass filter (OLPF), which slightly blurs the image at the pixel level to minimize moiré. This, of course, also slightly reduces overall image sharpness.
So when you use your camera’s monochrome mode, or convert a color digital image to monochrome in your computer, you’re working from a color image that was fabricated from a monochrome image using colored filters and complex image processing, and then turned back into monochrome. There must be a better way.
There is: a monochrome camera. The sensors in monochrome digital cameras don’t have color filter arrays because there’s no need. Thus, they record all the light (per the sensor’s quantum efficiency) that falls on each pixel; none is lost to color filters, so sensor sensitivity is, in effect, higher. There’s no demosaicing, and thus no color moiré and no need for the blurring AA filter. So images from a monochrome sensor are inherently sharper than converted color images, and sensitivity is higher. Of course, the monochrome camera can’t produce color images, so you have to consider your needs. Monochrome cameras are quite costly, so most photographers probably will be better off doing monochrome with their regular digital cameras—which can deliver excellent monochrome images despite the drawbacks. But for the monochrome connoisseur, the monochrome camera is the way to go.
Note that all digital images can suffer from aliasing—when you sample real-world scenes with a fine grid array, some aliasing (“stair-stepped” edges, moiré, etc.) will occur if the pattern of the subject is the right size and at the angle to conflict with the sampling grid. The finer the pixel grid, the less likely this is to happen, so more and more DSLRs and mirrorless cameras today are doing away with the AA filter as pixel counts go up. And medium-format digital cameras have never used AA filters. Aliasing—when it occurs—can be corrected in post-processing, as medium-format users have operated from the start.
Today, there are three basic monochrome digital cameras on the market, from Leica, Phase One and RED. They range in price from over $7,000 to over $40,000, and that’s their primary drawback. But in terms of monochrome image quality, they offer the best there is.
Leica M Monochrom
It’s a bit ironic considering the Leica cachet, but the M Monochrom is far and away the lowest-cost monochrome digital camera available today. It’s essentially a classic Leica M rangefinder camera, but with an 18-megapixel, full-frame (35.8×23.9mm) monochrome CCD sensor that has no RGB filter grid and no AA filter (but it does have an IR filter to cut off wavelengths longer than 700nm). Like all M-series Leica cameras, the M Monochrom can use the full lineup of legendary Leica M lenses (from 16mm to 135mm), and each frames just as it does on a traditional 35mm Leica M camera, thanks to the full-frame sensor. ISO range is 320-10,000 (and there’s even an auto ISO feature). Unlike most digital cameras, the M Monochrom has a histogram that displays the unprocessed, unmodified raw data, rather than data for a camera-processed JPEG image—very helpful for nailing those RAW exposures (the camera shoots DNG RAW files, as well as JPEGs). You can tone JPEGs in-camera. Digital aspects aside, the M Monochrom is a Leica M camera, with quick and easy rangefinder focusing, quiet operation, and a rugged body featuring top and base plates of machined brass and a housing manufactured from a single piece of magnesium alloy. Dimensions are 5.5×3.1×1.5 inches, weight is 21.2 ounces (body only). Estimated Street Price: $7,200. us.leica-camera.com
Sigma’s DSLRs and compact cameras with Foveon X3 image sensors don’t use Bayer filter arrays and demosaicing. Instead, they derive color from the fact that different light wavelengths penetrate silicon to different depths. Foveon sensors stack three pixel layers, in effect, the top layer recording short (blue) wavelengths, the middle layer, medium (green), and the bottom layer, long (red) wavelengths. (It’s really more complicated than that, especially with the latest-generation Foveon Quattro sensors, but it’s simpler to think of it this way.) The result is that these sensors record all three primary colors (as well as full luminance data) at every pixel site, no demosaicing or interpolation required—and, thus, no AA filter required, either. The result is sharper images than produced by Bayer sensors of equal horizontal-by
-vertical pixel count—and better monochrome images. The Foveon monochrome images aren’t as good as those from dedicated monochrome sensors, but they’re better than those from Bayer sensors—and the Sigma cameras cost a lot less than the monochrome digital cameras. The Sigma SD1 Merrill DSLR sells for around $1,999, the DP1, DP2 and DP3 Merrill compact cameras (with built-in wide-angle, normal and short tele lenses, respectively), for around $799, and the new dp1, dp2 and dp3 Quattro compacts (with wide, normal and short tele lenses, respectively) for $999. www.sigmaphoto.com
RED EPIC Monochrome
Many still photographers may think of RED as being only for video. However, RED’s DSMCs (Digital Still and Motion Cameras) can produce superb still images, as well as feature-quality video. The EPIC Monochrome features the RED Mysterium-X Monochrome sensor, a 30x15mm unit that can deliver 14-megapixel still images, as well as video up to 5K (5120×2700) at rates up to 59.94 fps. Native ISO is 2000; dynamic range is 13.5 stops (up to 18 stops with RED HDRx). Adapters are available for PL, Canon, Nikon and Leica lenses. RED offers two electronic viewfinders and LCD monitors from 5.0 to 9.0 inches, some with touch-screen capability. Images are saved to REDMAG 1.8-inch SSD units from 48 GB to 512 GB, or the RED MINI-MAG 512 GB. There are two versions of the EPIC Monochrome: the EPIC-M is handmade in California and carries a two-year warranty and a $25,000 price (Brain only), while the production EPIC-X (also made in the U.S.) carries a one-year warranty and a $20,000 price (Brain only). The RED EPIC-M Dragon Monochrome adds 6K (6144×3160) video, 19-megapixel stills and a 16.5-stop dynamic range to the above features, thanks to the Dragon-M sensor with interchangeable DSMC Monochrome OLPF. It sells for $31,500 (Brain only). www.red.com
Phase One IQ260 Achromatic
When DSLR users talk about full-frame, they mean 35mm full-frame: a sensor measuring about 36x24mm, the size of a full 35mm film frame. To medium-format users, full-frame means the size of a full 645-format film frame. That would be 6×4.5cm, in theory, more like 56×41.5mm in terms of actual image area. Phase One’s IQ260 Achromatic medium-format digital back (available as a kit with the Phase One 645DF+ camera body, or with mounts to fit many popular medium-format and technical cameras) features a 60-megapixel, full-frame medium-format monochrome CCD sensor that measures a whopping 53.7×40.3mm—more than 2.5X the area of a full-frame 35mm DSLR sensor and 1.5X the area of the 44x33mm sensors found in lower-end medium-format cameras. Besides the huge sensor size and 60 megapixels (and the resulting superb image quality), the back offers a 3.2-inch, 1150K-dot touch-screen display, 13 stops of dynamic range and ISOs from 200-3200. The back is ruggedly constructed of 100% aircraft-grade aluminum, and can be operated as an independent unit, tethered to a computer or wirelessly from an iPad or iPhone using Phase One Capture Pilot. Besides having no Bayer filters or AA filter, the IQ260 Achromatic has no IR cutoff filter, so it can also be used for infrared photography. Estimated Street Price: $44,495. www.phaseone.com