Life after Photoshop’s Photo-editing A-Z

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• C4K videoC4K, also known as DCI 4K, is 'true' 4K in that it has a horizontal resolution of 4,096 pixels, which is just a little over 4,000 (4K). Almost all 4K video actually shoot 4K UHD, which has a horizontal resolution of 3,840 pixels, a little way below that 4K resolution. C4K sounds more desirable, but the complication is that it's slightly wider than the 16:9 aspect ratio used by other common video standards (including 4K UHD).
• CacheThis is temporary storage space used by software so that files you need often can be accessed more quickly. It’s typically used for image thumbnails and previews in programs like Adobe Bridge and Lightroom. Sometimes cache files cause problems and must be purged or deleted, sometimes the storage allocation for the cache needs to be made larger in the application preferences to improve performance. Caches and cache files are generally expendable, but they are there for a reason and to speed up performance.
• Camera calibrationThis is both a panel in Adobe Camera Raw and Lightroom and a means of controlling the color rendition of a camera in a color managed workflow. Some studio and commercial photographers find camera calibration useful to achieve consistent and repeatable color rendition.
• Camera Kit (Analog Efex Pro)A mode in Analog Efex Pro, part of the DxO Nik Collection, where you can manually choose the filters you want to combine to create your own custom ‘camera’ look – hence ‘Camera Kit’.
• Capture OneCapture One is an all-in-one image capture (tethered shooting), cataloguing and editing software from Danish company Phase One. Born out of its medium format studio camera products, Capture One is now a professional RAW conversion tool for DSLR and mirrorless camera owners too. It’s a premium product and its closest rival is probably Adobe Lightroom.
• Cataloguing softwareSoftware designed to organise large collections of photos using an internal database that speeds up searches and lets you create ‘virtual’ albums and smart albums without actually having to move images on your hard disk. Adobe Lightroom is a good example, using a database ‘catalog’ to organise search and display images. Cataloguing software is more complex and powerful than image ‘browsers’ like Adobe Bridge, which simply show you the contents of folders on your computer.
• ChannelThe data used to create digital photos is split up into three colour ‘channels’ – red, green and blue, or ‘RGB’. These are then mixed to produce the millions of different colours required for lifelike pictures. In commercial printing, this red, green and blue (RGB) colour model is swapped for cyan, magenta, yellow and black (CMYK), which are the four colours used by commercial printing presses.
• Chromatic aberrationThis is a lens aberration that produces colour fringing around the outlines of objects near the edges of the picture. It’s very hard to eradicate completely from lens designs without making them extremely complex or expensive, but it is possible to correct chromatic aberration using software and many cameras will now correct it automatically as they process the image.
• Clarity 'Clarity' is a localised contrast adjustment much coarser than regular sharpening, which throws larger objects into sharp relief and can add some much needed definition and 'bite' to low-contrast scenes.
• ClippingFor photographers, ‘clipping’ is where the image histogram is cut off abruptly at one or both edges. It means that some image detail is completely lost in solid black shadows (shadow clipping) or completely white highlights (highlight clipping).
• CloningUsing a special clone stamp tool to copy pixels from a nearby area of an image to cover up an unwanted object or blemish. Cloning is something of an art, and some programs now offer simpler ‘content aware’ object removal.
• Cloud storageWhere you store or share images online as well as or instead of storing them on your computer. Cloud storage offers the advantage that your images are accessible everywhere as long as you have an Internet connection, though displaying and downloading images is of course slower than opening them on a hard drive, and uploading images in the first place is slower still. Examples include Apple iCloud, Dropbox and Google Drive.
• CMYKThis is a colour model used in printing processes, where colours are defined in terms of cyan, magenta, yellow and black colour channels (black is represented by the letter ‘K’). Desktop printers use CMYK inks but carry out the conversion from regular RGB photos automatically. In commercial printing, a designer will convert a regular RGB photo to CMYK to check the colour rendition and prepare it for printing.
• CollectionLightroom‘s name for its ‘virtual’ image containers. Some programs call them ‘albums’, but the terms ‘album’ and ‘collection’ are generally interchangeable. You use Collections to bring together related images with actually changing their location on your hard disk.
• Color adjustmentA good term to describe the HSL (hue, saturation, lightness) adjustments provided in many image-editors. You can use these to change the appearance of specific colors in an image while leaving the rest unaltered.
• Color BurnA layer blend mode found in most programs that support image layers. Using this mode produces an ultra-high contrast composite image based on the layer it’s applied to and the layer(s) underneath.
• Color castA color cast is where the colors in an image seem to show a general shift, for example the yellow-orange color cast you typically get with pictures taken in domestic artificial lighting, or the bluish skintones of portraits taken in shade under a blue sky. Color casts can often be corrected digitally, or prevented by choose a better white balance setting to take the picture.
• Color Efex ProColor Efex Pro is one of the plug-ins in the Nik Collection, now owned and published by DxO. It offers more than 50 filters which can be used individually or combined into a practically limitless array of 'recipes'. Both can be used to create single-click preset effects.
• Color Efex Pro (Nik Collection)A software plug in that’s part of the DxO Nik collection. Color Efex Pro offers a huge variety of preset image effects you can browse through and apply to your photos with a single click, but you can also adjust the filters manually and even stack them to create custom ‘recipes’. Color Efex Pro also offers localised adjustments via ‘control points’.
• Color fringingColor fringing is another term for chromatic aberration, an effect where the lens produces color fringes around object edges. It's a very common lens aberration which is often corrected digitally. With some sensors and lenses you may also get color fringing around the edges of objects with very bring backlighting, such as leaves on trees against a very bright sky.
• Color labels
• Color managementFor designers and professional photographers it’s often important to maintain consistent colour rendition from the camera, through to the computer display used for browsing and editing photos and right through to the final output device, generally a printer. Colour management tools use software ‘profiles’ and hardware monitor calibration and printer calibration devices to try to ensure this consistency of colour. It’s a complex process, and it’s worth pointing out that when images are going to be displayed on a screen rather than being printed, you have no control over the colour rendition of the output device. Many photographers don’t use colour management at all.
• Color modelThis is the system used by computers and other digital devices for defining colours. In photography, the RGB system is almost universal – colours are defined using red, green and blue colour ‘channels’. In printing, it’s CMYK, or cyan, magenta, yellow and black. Some image-editing processes use Lab mode, which consists of a ‘lightness’ channel and two (‘a’, ‘b’) colour channels.
• Color noiseOne of the two types of digital image noise and caused by random variations in the colour of neighbouring pixels. Colour noise is relatively easy for software to remove without any significant impact on the image quality. Luminance (contrast) noise is the other type, and much more difficult to remove effectively.
• Color profileA software file used in colour management processes that describes the properties of a specific device so that your computer can correct or ‘normalise’ the way it displays or prints colours. If you don’t use colour management in your workflow, you don’t need to worry about this.
• Color sensitivityThis is a property used often in black and white conversions from a colour image. You’ll find it in programs like Silver Efex Pro, Capture One and others, and it changes the way different colours are converted into shades of grey. For example, you can use it to mimic the effect of a red filter in black and white photography, by reducing the strength (sensitivity) of the blue/cyan colours in the image and increasing the strength of the red/orange tones. In the old days, you’d use the Channel Mixer in Photoshop to achieve the same thing in a cruder fashion; these days, black and white conversion tools offer more control over a wider range of colours.
• Color spaceDifferent devices can’t always display the same range of colours, so your camera may be able to record a wider range of colours than your computer monitor or tablet can display, for example – in other words, the monitor offers a smaller ‘colour space’. To get round this, there are two main RGB colour spaces you can work on. The sRGB colour space is a smaller, universal colour space that practically any device can match. Adobe RGB is a larger colour space that your camera and printing systems can capture but your monitor probably can’t, which means some complex workarounds and pitfalls and really needs a switch to a more complex colour managed workflow. sRGB is the simplest solution, and (though some will debate this) you’re unlikely to see any real advantage to Adobe RGB in everyday photography.
• Color temperatureA traditional technical measurement for the white balance setting that uses temperature values in degrees Kelvin rather than named presets like ‘Direct Sunlight’, ‘Cloudy’ and so on. Colour temperature is used for choosing and controlling the colour of photographic lighting equipment and you can use it an alternative to white balance presets on more advanced cameras.
• CompositionThis is the art, or skill, of arranging the objects, perspective and framing of a photograph to achieve the desired visual effect. There are a number of 'rules' of composition, including the rule of thirds, the Golden Mean and various other photographic truisms that may or may not prove useful.
• CompressionA software process that reduces the storage space taken up by photo or video image files. It comes in two type: ‘lossless’ and ‘lossy’ compression. Lossless compression is used by TIFF files, for example and retains all the image data but does not produce the biggest savings. Lossy compression is used for the JPEG format and produces much smaller files, but some data is lost in the process – though this may not be visible in real-world viewing conditions.
• Constrain Crop
• Content-awareImage repair tools that can ‘intelligently’ paint over unwanted objects and blemishes using surrounding image data matched to the area being covered up. Photoshop has content-aware repair tools, Affinity Photo offers an Inpainting brush, MacPhun’s Snapheal offers a choice of intelligent object removal tools.
• ContrastContrast, in its simplest sense, is the different in brightness between two tone. In photography it's usually taken to mean the brightness range of a picture – the difference in brightness between the brightest and darkest parts of a picture.
• Contrast Color Range (Color Efex Pro)A filter in Color Efex Pro which intensifies the difference in intensity and contrast between colours. It’s effective in landscape photography, for example, for intensifying blue skies without increasing the saturation of the image as a whole.
• Contrast filterA colour filter used in black and white photography to change the shade of grey that colours are reproduced as. They’re called ‘contrast’ filters because they can change the contrast (in shades of grey) between different colours.
• Control PointA special selection and adjustment tool used by the Nik Collection plug-ins and DxO PhotoLab, control points operate over an adjustable circular radius and select only tones similar to the area under the central target. You can use them to adjust Brightness, Contrast, Structure, Saturation and more.
• Converging verticalsA type of perspective distortion caused by tilting the camera upwards to photograph tall buildings. It’s worse with wideangle lenses because they let you stand closer, so you tilt the camera even more. The only solution is to compose the shot with the camera completely level.
• CopyrightYou own the copyright in any photo you take, though if you photograph a model or an important building, you may not have the right to use your photos commercially without their permission (or ‘release’). Some cameras can embed a copyright message automatically in each photo’s metadata.
• Corner shadingCorner shading is another term for 'vignetting', where the corners or the edges of a picture look darker than the center. This is a common phenomenon with lenses, though today's lens designers work hard to eliminate it. Some photographers feel it can add to the 'look' of an image, however.
• Creative Cloud (Adobe)Adobe’s online image sharing, storage, synchronisation and collaboration service. Many of Adobe’s workflow tools now rely on its Creative Cloud services.
• Crop factorUsed to work out the effective focal length of lenses on cameras which don’t have full frame sensors. You multiply the actual focal length by the crop factor to get the effective focal length. The crop factor of an APS-C camera is 1.5, so a 50mm lens has an effective focal length of 75mm.
• CroppingThere are two main reasons for cropping photos, one creative, one practical. You may want to crop out unwanted objects near the edges of the picture, or you may need to crop it to fit different print sizes and aspect ratios.
• Cross Processing
• Culling images
• CurvesCurves are one of the most fundamental image adjustment tools in photo editing software. They're used to shift different parts of the pictures tonal range to make them darker or lighter, though they can also be used for color adjustments.
• CutoutWhere an object in a photo is cut out from its surroundings using a selection or a mask so that it can be added to another image or placed against a plain (usually white) background.