Understanding Image Sensor Characteristics
Taken with a Nikon D50 and AF Zoom-Nikkor 70-300mm f/4-5.6G lens
By 'exposure' we mean the amount of light that falls onto the film, or CCD if you are using a digital camera. In modern cameras the exposure is usually set to automatic by default and, most of the time, it can be left there and will produce beautiful pictures. There are times though, when the lighting conditions are difficult or we want to produce a particular effect and it would be nice to understand what is going on 'under the hood'.
The problem with all types of film and recording media is that they cannot record the entire range of contrast (black to white) that the eye can see. Especially when you take into account that the eye is constantly adjusting to cope with high contrast. On a sunny day if you look into the shadows of a scene then into the bright areas, the iris in your eye will quickly adjust so you can see detail in both.
Faced with the task of recording as much information as possible, the camera will try to average out all the light levels and expose the film accordingly. As burnt out highlights are normally considered uglier than black shadows, the camera, left to it's own devices will normally err on the dark side. Which is no good if you are shooting someone's face against a bright sky. It's the person's face you want to see, and you don't really care if the sky is white.
Location
Chendering Fisheries Garden,
Kuala Terengganu
21080 Kuala Terengganu
Terengganu, Malaysia
Image Sensor Linearity & Saturation
Image sensors consist of either a CCD or CMOS and output signals according to the received light intensity. However, the signal increase and stops at a certain light intensity. This is called saturation. This causes RAW data to whiteout. However, this does not mean that you can increase the light intensity to the image sensor up to just before the saturation point. When the light intensity is outside of the range proportional with the output signal, color reproduction will be low.
Usually, cameras are designed to use only this proportional area for creating JPEG images. However, this proportional area contains the tolerated area. This tolerance area is determined by the camera maker, but it does not mean that you can tolerate it.
If you cannot accept the tolerated area, you can adjust the exposure to your tolerance level. You can take underexposed pictures up to the tolerated area. If you cannot accept your camera's tolerated area, you should think about getting a new camera. When you take underexposed pictures, you may be able to avoid color reproduction loss, but noise may increase. You must determine your balance between color reproduction and noise based on your camera sensor's performance.
In addition, you may be able to go over the tolerated area determined by your camera depending on the object being photographed. In such cases, you can use overexposure according to the area mentioned in "Sensitivity Adjustment Potential" so that you can have clean images with less noise.
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Labels: AF Zoom-Nikkor 70-300mm f/4-5.6G, Chendering Fisheries Complex, Nikon D50, People, Photography
