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). 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. But for the monochrome connoisseur, the monochrome camera is the way to go. 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. Of course, the monochrome camera can’t produce color images, so you have to consider your needs. So images from a monochrome sensor are inherently sharper than converted color images, and sensitivity is higher. There’s no demosaicing, and thus no color moiré and no need for the blurring AA filter. 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. The sensors in monochrome digital cameras don’t have color filter arrays because there’s no need. 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. This, of course, also slightly reduces overall image sharpness. 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. Second, the demosaicing process produces aliasing-moiré, color artifacts and the like. First, a lot of light is wasted, since the colored filters block two-thirds of the light from reaching each pixel. However, the demosaicing process does have some drawbacks. 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). 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. 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. Each pixel can detect how much light strikes it, but not what color that light is. Why Monochrome Cameras Do It BetterĬonventional image sensors consist of a fine grid of millions of pixels or photodiodes that record light in proportion to its intensity. (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. Photoshop’s Channel Mixer gives you tremendous control over the tones in the image. And you can convert any digital image, whether it was shot recently or it’s a scan from an old Kodachrome transparency. 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.
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