Long exposure with digital camera
Digital camera - long exposure test
Digital camera - long exposure test
|
|
 |
 |
 |
 Online Photo Courses t-photo book store |
|
For buyers of "Digital Photo with Powershot G6: We shall add this topic to the new revision later and free update will be arranged as usual.
Can we use digital camera to take what we have done with traditional camera is something in our mind. Of course, that is not a fair comparison. With digital imaging, we have a lot of applications that never been done or very difficult to achieve with traditional method. Each has its own goodies. However, it is a must to explore so that we have what we can and cannot do with the digital camera. Recently, I find that there are questions about the long exposure problem. In the film days, we have faced with the reciprocity with long exposure. In general, it is for astronomical photo that exposure might in hours. The reason is the exposed grains block the light leading to under-exposure result. Solution is by using a wider aperture or longer exposure. Some even needs to use ice to cool down the film. There is a B/W film, Technical Pan by Kodak that said to be the only film without reciprocity failure. I had tested this film when it came out in early 80's to replace the previous High Contrast Copy film. The resolution is so high that for a certain period, the USA government had banned it for export because it could be used for spying. For our photos, it is not common to have exposure time longer than one hour. When we take photo of city night scene, it may require exposure time about 8 to 15 seconds for the lamp light of cars to form long bright lines. The time required for such shots depend on the distance. Except at a very long distance, 15 seconds is more than enough. |
The exposure is by manual. It is better to have a test to find the setting. Priority is to have the exact effect that we want; that is, the car lamps formed a bright line. Usually the other areas may be over-exposed. We need to use software to adjust the brightness and contrast. The level of adjustment depends on personal choice. It is advised to use the smallest aperture for the best depth of field. In fact, we have to because of the long exposure time. Furthermore, the lowest ISO and ND had chosen for this test. |
Will long exposure affect the color saturation?
The Image 5 looks sharper because we used f/8 for it. The Image 8 has a higher contrast because the ND is off. Besides the mentioned difference, it seems that the color saturation of all four photos is almost similar. These are taken with room light (on ceiling) with custom white balance. For better effect, we can use desktop lamps to have a stronger lighting and better colors. According to this test, we find that the longer exposures from 1/30 sec. to 15 sec. have no change of color saturation. It would not be a reason for use to venture the long exposure. But we must remember that the long exposure for freezing effect remains effective. |
