How to expose accurately for beginners

Introduction: The definition of exposure, if explained scientifically, is: the intensity of light multiplied by the time the light acts on. The "intensity of light" in the definition refers to the intensity of light irradiated by the CCD, that is, illuminance (I represents illuminance, and the unit is lux). The "time the light acts on" in the definition refers to the time the photosensitive film is illuminated by the love ray, that is, the exposure time (T represents the exposure time, and the unit is seconds). Exposure is measured in lux seconds. Using E to represent exposure, the exposure formula can be obtained as follows: E (exposure) = I (illuminance)? T (exposure time). According to this formula, if you want to obtain a certain amount of exposure, the greater the light intensity, the greater the exposure. The shorter the time; the smaller the light intensity, the longer the exposure time. If the light intensity is doubled, the exposure time needs to be reduced by half. If the light intensity is 2, the time is 4, the exposure is 8; if the light intensity is 4, the time is 2, the exposure is still 8. When shooting with Fuji S2Pro, first measure the water surface and manually adjust it to this value. The exposure will appear as a silhouette effect. How to expose accurately for beginners

Regarding equal exposure:

We clearly understand this simple truth: opening a larger aperture is better than shrinking a smaller aperture. Allowing more light to pass through the lens and onto the film, a lower shutter speed allows the light to stay on the CCD for a longer period of time than a higher shutter speed. This can evolve into the following situation: the combination of aperture f/1.8 and shutter speed 1/500 second will produce the same exposure effect as the combination of aperture f/4 and shutter speed 1/100 second. They are consistent with the exposure obtained by combining a mid-range aperture of f/8 with a mid-range shutter speed of 1/25 second. This is called "equal exposure".

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The exposure amounts of the above three exposure combinations are equal, the density reflected on the film is consistent, and the density reflected on the CCD The tonal levels, tonal restoration and reproduction are consistent. However, there are two important differences in the picture effects between the three of them: First, the aperture size creates different depth of field; second, the shutter speed creates different clarity levels of moving images.

From the principle of equal exposure, we know that equal exposure with different exposure combinations can achieve the same exposure effect with the same film density. However, in photography practice, one should choose the best set of exposure combinations among several exposure combinations that can produce the same density to express the photographed subject, depending on the subject matter and the subject being photographed. This is the concept of selective exposure.

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The origin of a film that is satisfactory in terms of exposure control?

Those experienced photographers , we know from the theory and practical experience of photography that although each set of shutter and aperture can produce the same amount of exposure effect, the depth of field and the clarity of moving objects in the picture are very different. The specific exposure combination to be used must be carefully considered. Should you use a smaller aperture to obtain a clearer range of the deeper scene? Or use a higher shutter speed to capture a frozen image of the subject? Or use a very short depth of field to blur the background to highlight the subject? Or use a slower shutter speed to enhance the dynamics of moving objects? Wait.

What is accurate exposure?

The meaning of correct exposure should simply be: exposing the CCD to the appropriate amount of light at the appropriate time. Speaking of exposure, we must first talk about Adams' regional exposure. One of the greatest contributions of American photographer A. Adams, the master of landscape photography, to the photography industry is the creation of the concept of "area exposure". Not to mention, I actually don’t understand it all myself. The theory inside is enough to write a book. But now my shooting is based on this understanding.

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Why can we see the changing geometric structure of images?

Friends who have learned sketching will easily understand that pictures are nothing more than It is a continuous transition from bright white highlights to saturated mid-gray to full black shadows. This transition allows us to discern the outline of an object. The most traditional shooting techniques are still the most effective in the digital realm. When you see a picture and what do you want to express, that is to say, if you want it to reflect the most saturated colors and richest details, just point and test it, and then expose according to the test value, and the resulting film will generally not Let you down. Of course, if you want other parts to also show some details, you must use reflectors and light-absorbing plates to control these places within the tolerance range of your CCD, or change the angle and wait for changes in light to reduce the light ratio. . The opposite is also true. If you want a certain part to appear pure black or pure white, then make these parts deviate from the exposure value by more than 5 stops, and you can see what you want to see. Now you understand how important point measurement and manual measurement are to a camera.

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Of course, actual shooting is not that simple, especially when shooting portraits and documentary films. You have to limit the light, and the light also limits you. , except for indoor still life, perfect light is hard to come by. But opportunities are often fleeting. At this point, experience becomes critical. Exposure bracketing is an effective tool. But it’s not a panacea, at least bracketing metering cannot change the objective light ratio. Bresson said: You have to constantly change the angle? Changing the angle is not only to change the composition, but often to improve the restrictions of light on you. There are so many things that can be used, such as the reflection of water, white walls, etc., including many unforeseen situations, such as thin clouds that can soften the sun.

At this point, I can’t continue writing. My level is still too shallow. There are many things that can only be understood but not expressed. My own thinking is still important. As the old saying goes, the key is your brain behind the camera.

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