Imperfection in Images - II Look for dark regions and burnt areas

Tuesday, January 09, 2007

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DARK REGIONS

This is a more common imperfection, and also more obvious than the previous one - soft images. It is likely to occur when you are shooting indoors with single flash and no reflectors, or when you are shooting outdoors when the sun is high.

Although it is a very common imperfection and easy to spot, beginners are often unaware of it because our eyes tend to ignore these spots. Here are some examples of dark areas in the images.



Look at the dark patch to the left of the girl's back. You see a narrow dark strip which is nothing but the shadow created by the flash. Similar effect can happen when you are shooting with single source of light, even without flash.



The image on the left was taken in the mid-day sun. You can see dark shadows which have completely hidden the eye of the person. You can see ugly dark spot under the nose of the boy to the right.



Besides portrait images, this can also happen easily when you are shooting buildings, or landscapes in general. Below is an example of a structure shot in harsh sun, which has cast shadows to the right of each pillar.



And below is the image of last sunlight of the day falling on a mountain peak. It is a beautiful sight and mountain peak is glowing beautifully. But note that the bottom portion of the image has gone completely dark, spoiling the whole image. Such problems can occur frequently when shooting sunrise and sunset.

PREVENTING DARK AREAS

1. When shooting people indoors, look carefully for shadows on the face. It becomes evident after some practice. Avoid using flash and use the tripod where possible. Tripods and indoor light can be used to make some great portraits, but setting up the light properly is important(That is another topic altogether). If you have to use flash, try to complement with existing light in the room such that you won't get shadows. If you don't have a wall or any objects behind the person, you can avoid shadows to some extent. Do not shoot with a single artificial light source like a light bulb. You should install light sources in opposite/multiple directions such that they can eliminate shadows.
2. Avoid shooting outdoor when sun is high. This applies to all kind of photographs - people, buildings or landscapes. Early morning and evenings are the best time to shoot outdoor. If you are shooting people or close-by objects in the sun, you can also use fill-flash to prevent shadows. That is, turn on the flash which will light up the areas that would otherwise appear as shadow.
3. When you are shooting landscapes, especially sunrise and sunsets, sky and the ground will be at different levels of brightness. So if you shoot for the sky you will get completely dark areas for ground, and if you shoot for the ground, your sky will appear completely white. The best way to prevent it is to use Graduated Neutral Density filters, which can stop some light from the sky while allowing all the light coming in from the ground.
4. When the exposed image has some dark areas that are not too bad, it can be recovered during processing by tools such as Shadows/Highlight tool in Photoshop.

BURNT AREAS

The area in the photograph that appears completely white because of over-exposure is normally called burnt. This is a more common problem and difficult to prevent. Many high end point and shoot digital cameras and almost all DSLRs warn the photographer about burnt areas in the photograph by making that area blink continuously. You can also verify over-exposed image using the histogram.

Below is an example of burnt image. In this picture, the sky appears pure white because it is over-exposed. But actually sky was overcast and had some colors and was not pure white.



In the image below, some parts of snow appear pure white and patterns in the snow are not visible.



The trouble with burnt images is that it is not possible to recover any details from that area. In image like the ski slope above, a bit of burnt area may not hurt, but burnt sky can often result in bad images.

PREVENTING BURN

Burns are not so much of a problem indoors as dark areas. Here is some tips to prevent getting burnt images outdoors.

1. What applies for preventing dark areas applies to preventing burnt areas too! Do not shoot outdoor when the sun is high. Contrast in the frame can be high in such times and can result in some burn. Using Graduated Neutral Density Filters when sky and ground share the composition also helps.
2. Expose to the brighter areas. That can prevent burns, but other areas in the frame may turn out darker than desired. Since it is easy to fix such situation in software than what you get when you expose to darker areas, this is preferable.
3. The best thing to do is to evaluate the contrast in the frame, and if you can't get a good image without getting too much of dark or bright areas, re-compose the image or come back when the light is favorable.