- Compositing - Putting people shot in studio into other locations seamlessly, especially full-length shots. This involves working with perspective, colour correction and masking.
- Strong Tones - The kind of lighting and dodging and burning techniques that give edgy yet smooth sculpting to people and locations.
- Beauty Retouching - Creating the glossy mag cosmetic advert look by fixing skin, hair, eyes, make up etc.
LIGHT: has many qualities and most of them can be adjusted in the computer.
Direction: When images are composited together, the light must come from the same direction. Sometimes an element can be flipped to achieve this, but it is very difficult to realistically match a figure shot a noon with a scene shot in the low angled light of late afternoon. If this must be done, the best thing is to reduce the contrast between the highlights and shadows as much as possible to make the difference less obvious.
Intensity: A figure illuminated by direct flash or bright sun has sharply defined areas of light and shadow and strong highlights. The same figure in open shade or on an overcast day with will look softly modeled. When matching elements for intensity of light, it is easier to increase the contrast to simulate more intense light than to achieve soft modeling from an image with bright highlights and deep shadows.
Kelvin: is the color temperature of light. The ‘white’ sunlight at high noon and a daylight flash are about 5500 Kelvin. The bluish light of open shade on a clear day is about 8500 Kelvin. The warm light of a tungsten household bulb is about 2800 Kelvin, and candlelight is about 1800 Kelvin. You can correct for some Kelvin differences in the computer, but where only shades of orange or blue were registered on the film, there are no other colors to bring out.
Color: The color of light is effected by the particulates in the air, the time of day, and the reflections from colors around the image. It can also be given color if it comes through things like colored glass. As the sun gets lower in the sky it must pass through more and more of the earths atmosphere with its particulates, thus the lower the sun is, the more it is colored by particulates, giving us the red light of some of sunsets. Adjusting the color of light is fairly easy if it is unidirectional, but reflected sources of different colors can be difficult to match.
Reflected Light: of various colors, as the Impressionists have shown us, is an important part of the coloration of the objects we see. Rough surfaces with many planes have more varieties of light. Fortunately, most people are not as visually attuned to secondary light sources as to the predominate light source, but if you are an artist, you can try your hand at adding the appropriate tints (always saving your work before you start!) When you are matching similar surfaces, both need a similar mottling of colors, and to achieve this you can use the clone tool at an appropriate setting to borrow from one for the other.
ATMOSPHERICS: refers to the way particulate matter in the air affects the appearance of things as they get farther away from us. Fog is perhaps the best know atmospheric, but all air contains some amount of particulate matter. In clear air, distant scenery will take on a bluish tint. Smog will turn scenery more and more yellowish the farther away it is.
- A figure photographed on a clear day cannot be composited into a scene photographed on a hazy day without making adjustments to the figure by desaturating the color and blurring the image appropriate to how near the figure is to the viewer in the scene. It is rarely as successful to intensify the colors and sharpen a picture taken in haze so it will match an image taken in clear light.
- Atmospherics will be discussed again under Aerial Perspective.
Wind: The speed and direction of the wind affect everything from the way clothes drape and grass bends to how hair blows. All these elements should be matched for a realistic composite, if the wind is noticeable.
- Direction: When images are composited together, any visible effects of the wind should agree as to direction. If the wind is strong, people will lean against it and trees will bend with it. Also in a strong, and especially a cold wind, people squint up their faces and angle their backs against it.
- Force: A gale force wind has very different and more visible effects from a light breeze, and requires more careful matching.
PERSPECTIVE: Scientific perspective is an element unique to Western art and has only been around about 500 years. However, because our brain uses spatial relationships and linear clues to orient us, if these are incorrect in an image that is supposed to be realistic, it has a very unsettling effect.
- Aerial Perspective refers to the way that particulates in the atmosphere cause objects to get paler and less distinct the further away they are from us. You must therefore blur and desaturate sharp-edged, brightly colored elements when compositing then into the distant part of a scene that has noticeable aerial perspective.
- Linear Perspective refers to the way lines converge to a vanishing point. Temporary guidelines will help you aligning objects such as buildings, and place people so their feet seem to be on the ground. (Cutting off the feet will not disguise the fact that the figure is standing in thin air.)
FOCUS: When matching elements that come from photographs, you will have to match the focus of elements that are at the same depth in the picture. This may require sharpening or blurring of one or more elements. If the depth of field is very narrow, you may have to blur just part of the composited element, such as the sides of the face.
EDGE DEFINITION: The sharp edge of a computer cut out looks very unnatural, and this is best corrected with the blur tool set to the right size and amount to create a match with the edges of the other elements.
POSITION: Composited elements must be placed in the proper relationship to each other. This is most easily done by pasting in the things that are farthest away first, but you may have to create a selection and past into it so that elements come in the right order.
PROPORTION: is the size relationship between elements. A child composited next to an adult must be proportionately smaller. Calculating this gets more difficult when objects of different sizes are also in linear perspective to one another. First determine the size they would be on the same plane and then adjust the size of the more distant object in accord with perspective lines. Errors can be caused by not knowing how large an element really is- is a destroyer bigger than a cruiser? Only research can help here.
GRAIN & NOISE: can be very difficult to make uniform among composited elements. Different types of film, and the same film at different enlargements, have different sizes and structure of grain. Due to the nature of scanning, the grain in film is emphasized, and it is particularly visible in pale, even-colored areas such as skies.
- Various program functions such as Despeckle, Remove Mars and Scratches, Blur, and Median can smooth out grain and noise in areas like a selected sky, but if used generally these functions can blur the image out of sharp focus. In some cases, you will need to add grain to make a match.
- When retouching with paint tools, or compositing a non-photographic element, that area can look slick and flat because it lacks grain or noise. Adding carefully chosen and adjusted HSV noise can be done straight, or semi-transparent, and/or blurred, and to one or more of the color channels.
TEXTURE is one of the most important and difficult elements to match. It is often necessary to create areas of texture to fill in where an overlaying object has been cut away, or where something must be extended.
- Texture can be matched between composited elements in a number of ways such as a carefully adjusted clone tool, a semi-transparent paste, or painting the texture.
- In cases where it is necessary to put texture on top of an element without obscuring its original shape and shading, the multiply setting or procedural blend may work very well
FACES: When repainting parts of a face, the lack of the variegated colors normally found in the skin tones can make that area look unnatural, and cloning from other areas of skin can improve this.
REALITY: requires knowing or researching the subject. It is very easy to mistakenly composite elements from different cultures, time periods, or situations. Sometimes this is accepted, as in Western movies where 19th Century cowboys ride on 20th Century saddles, and King ArthurÕs knights sit down to dinner in their battle armor. But if accuracy is important, research is essential.
- Location requires that the elements could be found in the same place- there are no tigers wild in Africa, and tropical foliage is not native to northern climes, nor would an English country manor have adobe walls.
- Time Period means watching out for anachronistic elements- telephone poles outside castles, TV antennas on top of Victorian residences, clothes and jewelry that were not worn at the time you wish to recreate. Fortunately some things are usually quite easy to remove in the computer.
- Social Context: You would not put a Rolls Royce in the carport of a tract house. You must understand the context or mistakes will be made.
- Season: If the season is apparent, then the elements must agree. Not only the folliage changes with the season, but the quality of the light, and in latitudes away from the equator, the maximum height that the sun reaches in the sky. In a Canadian winter you will not find the sun over head at noon, but rather it is always low in the sky and moves around the horizon.
- Weather: If the weather condition is apparent, then the elements must agree. Sometimes you can create effects like rain and snow so they match across the elements.
- Time of Day is shown by the direction and color of light. Be careful of having sunrises and sunsets from the wrong direction- a sunrise over the ocean viewed from California just doesn’t happen.
NOTE: When compositing, remember those art school rules:
- Do not to cut figures off in awkward or pricise places, such as at the ankles wrists.
- A composition that is too perfectly balanced looks unnatural and often is not aesthetically pleasing.
Taken from: http://www.dlwaldron.com/lessons.html
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