12th December 2008, 04:54 AM
Guide: Use of backlighting
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Status: still editing and re-verifying old information
Last edited by zoossh; 12th December 2008 at 05:01 AM.
12th December 2008, 04:56 AM
Re: Guide: Use of backlighting
Light interplays with space and time
Direction of light
This relationship dictates the spatial relationship between light and subjects in the frame, and constitute part of composition in the spatial relationship of a 3D vision, by giving a dimension of highlight, shadows, gradient, contrast and contours.
Light can be diffuse or directional. Diffuse lighting occurs when there is multiple light source, or if there is sufficient multidirectional reflection, for example a cloudy day which we call an overcast (day/weather/lighting). Directional light is more easily understood, usually from the sun or 1-2 spot light.
Directional light casts shadows from textured surface or contoured subject where light cannot passed through, or less light is transmitted compared to the areas directly illuminated. Very often, they are not totally dark because some degree of reflected light still manages to illuminate the shadow areas to some extent.
The direction of light can be from the front, at an angle (quarter), from the side, top, base. Light that is perpendicular or tangential to the surface of the troughs and peaks of a subject's contour, i.e. overhead, will illuminated most of the surface, whereas light that is parallel to the troughs and peaks of a subject's contour, i.e. shining on a slope, will illuminated the slope and leave the other side of the slope in shadows. In time, I will find some illustration to demonstrate it better than words. Nonetheless, this concept invariably means that low angled light in landscape and travel during the peri-sunrise duration (note once the sun rises above the mountains for certain regions, they are usually already at a higher angle) and the late afternoon, is sought after for its ability to reveal texture.
In the aspect of portraits, the light source can be either ambient, e.g. from the windows or an existing room light, or added from photographic lights that can be either continuous or flash. The direction is controlled by the photographer, usually an experienced studio worker, where multiple light sources and reflectors are applied to give the desired effects.
Likewise in product lighting, sources such as base illumination can be applied.
In the realms of non studio photographers who does not use flash or not familiar with flash, like me, the sun is our light source and everything follows the sun. Whether i shoot people, streets, events, scenaries buildings or still life, i need to know where is the sun in relationship to my subjects. The angle of the lighting is an estimate, and is usually divided into midday or overhead lighting versus low angle lighting.
What is backlighting?
Backlighting, is also called contre jour in French. It refers to a strong light source that is facing you head on with your subject between you and the light source, thereby blocking the light and casting a silhouette and/or a shadow (the shadow may not be within the frame).
When is backlighting used?
Backlighting brightens up the distant background and makes the darker subject stands out. It creates contrast of tones at the interface between subject and background, thereby improving impact.
Alternatively for a translucent material, backlighting act as a direct illumination of the internal texture of the material as compared to front or side lighting that illuminates the surface of a solid opaque subject.
Last edited by zoossh; 12th December 2008 at 05:00 AM.
12th December 2008, 04:58 AM
Re: Guide: Use of backlighting
Sharp edge solid silhouette
A sharp edge subject such as a sign board can show up as a total silhouette that is black because it blocks most of the light, in contrast to the remaining foreground not blocked by it. As our sensor has limited latitude, the tonal contrast between the subject and the illuminated background and foreground would be very high, thereby allowing a silhouette to be easily formed. That tonal contrast would be maintained unless a graduated filter is used to balance the exposure, otherwise the effect would be up to the degree of tonal contrast and how much exposure the user allows for the scene. If a scene of highlight (sky) and dark areas (foreground of a downcoming slope of a hill blocked by vegetation on the peak) is underexposed, the highlight will become midtone in intensity, and the dark areas will become black shadows.
Sharp edge semi silhouette
When the tonal contrast between the subject and the illuminated surrounding is not very high, achieving the surrounding in midtone may not necessarily made the subject totally black, rather just underexposed. Semi-silhouette is almost akin to underexposed areas, except that instead of being a foreground, it stands out against the illuminated background.
The degree of tonal contrast decides how much details can be seen in the underexposed semi-silhouette.
The aesthetic choice of whether to have a total black silhouette depends on whether the form of the silhouette is recognisable, whether there is interesting details to be revealed in the shadow and whether the tonal differences will allow any details to be retained in the shadows with a suitable midtone sky.
with permission from photographer of the picture, stupidbloke : sunset pose with girls!
Takes for example, this is a semi low angle sunset shot that is from the left, lighting up on the left (right side of the people from their point of view). If they are directly illuminated, they should be brighter than that, but they are not that bright, compatible with reflected illumination.
The user spot metered for the sky and underexposed for the sky from manual exposure settings gauged from the exposure meter on the viewfinder. This gives a dark midtone of the sky and a semi-silhouette of the people standing within. There are sufficient details in the semi-silhouette to add interest to the picture. We can tell the colors of clothes they are wearing, and interesting accessories such as the necklace and the belt. In the middle where there is three people standing close together, having a semi-silhoutte tells them apart.
In the areas where the tonal intensity is already low, such as the hair, they become solid silhouette. The hair that is blown up in the wind in the first and fourth girl in the row from the left adds further interest and mood.
Round edge enhancement
Upon rounded edges, there will be spilling of light, that is somewhat similar to a low angle shot or a side-lighting.
Thin structures, such as hair and fur may stand out of the border of the subject against the back light. With a mixture of light spilling and translucency, the fine details will be gently enhanced. This is not achievable by just sharpening in photoediting, which just create a coarse halo around the structures.
Tiny structures such as dust and sand in the atmosphere also enhances from a mixture of light spilling and reflection of light.
Backlighting through translucent material
Upon translucent surfaces, such as the leaves that does not overlap each other, contre-jour lighting can also emphasize texture through a demonstration between the thicker and more opaque portions versus the thinner and more translucent surfaces, such as the veins of the leaves and the subtle texture of a cloth or a petal of flower. Moreover, such surfaces may curved with areas that is more perpendicular or more parallel to the light source, thereby giving a difference in thickness in the direction of light, creating depths.
with permission from photographer of the picture, luosangjian : North Xinjiang - Habahe & Jeminay
Nikon D80, focal length 52mm x 1.5, ISO400, EV-1/3 stop, f/11, 1/320s
The lighting condition in this picture illustrate a combination of different subject relationship to light.
The sun is out of the frame, but is low, causing a bright background in the low horizon fading into darkness. The light comes from the left, as can be seen in the illuminated left side of the clouds and non-illuminated right edge of the clouds. There is a rim of light around most part of the clouds, presumbably representing thinner thickness at the peripheries, allowing light to shine through.
The silhouette does not just apply to the tree that stands out against the brighter background. In this case, the ridge of the land slopes downwards towards the photographer hence the low angle light does not illuminate the foreground as the ridge is higher and blocks the low angle light. While the tree have branches and leaves that are outlined in the full silhouette, showing a recognisable form, the foreground can be devoid of all recognisation of details should it be in full silhouette. It is subtlely handled with a faint suggestion of a road in the foreground in the lateral 2/3 of the frame to the right of the tree. It is a faintly detailed semi-sihouette, if your screen is not well calibrated with a proper gamma, you may not see it.
Some parts of the trees have the leaves in shadow, while some parts show a dark yellow. This may be due to certain portions of the trees that are thinner with less leaves. Non-overlapping leaves may allow some tranmission of light. A better example of such differential illumination of leaves is coklat's shot that is more like a high key picture.
with permission from photographer of the picture, coklat : My journey back to Semarang
Last edited by zoossh; 12th December 2008 at 04:59 AM.
12th December 2008, 04:59 AM
Re: Guide: Use of backlighting
Backlighting and potential problems or difficulty
Problems that may arise from using backlighting includes
1. having increased chances of flares.
- Some would recommend using a lens hood to reduce the amount of light that hits the lens elements directly.
2. overall overexposure and inability to contain high tonal contrast within sensor latitude,
- especially prominent when the centre of the light source is included in the frame
- occurs when a semi-silhouette or more midtone details are desired in the shadow areas while finding difficulty in avoiding overexposure of sky
- less likely an issue for full silhouette, except for the early-mid morning's low light
- on the other hand, if sky is metered for in matrix or spot metering, there is likely an underexposure of the foreground which may not be desired if shadow regions are not desired for the subject, e.g. face. This depends on whether in a backlighting situation, is there sufficient illumination of the subject in shadow to give sufficient details desired. some people uses fill flash to cope with that.
- control of exposure requires understanding of exposure in relation to the various factors.
- to overcome high tonal contrast, either HDR or GND can be applied. GND will cut down overall exposure too.
- can try to hide the light source behind an opaque structure, either to allow part or whole of it to be blocked.