Master the ISO of SLR shutter aperture

One of the main functions of aperture, shutter and ISO is to combine an optimal exposure.

Exposure is a very important concept in photography, that is to say, how much exposure the photographer needs for the photosensitive part. There is no exposure meter, and there is a general rule called "sunshine sixteen" rule.

It means that when shooting at noon on a sunny day, when the film or exposure is set to ISO 100 and the shutter speed is1100 seconds (that is, the aperture is set to F 1/ISO value), more accurate exposure can be obtained.

Then it is necessary to understand the increase and decrease of these three factors. Shutter and ISO are both multiples of 2.

For example, the shutter of1100 is 1/200 by adding one gear, 1/400 by adding two gears, and so on, 1/800, just like ISO,100.

And the aperture is 1.4 14 times, 1.4 aperture minus one gear, minus two gears is 2.8, minus three gears is 4, and so on.

According to the sunshine 16 rule, we can calculate as follows:

1, if shooting at noon on a sunny day, we know that ISO 100, shutter1100, f/ 16 are all relatively accurate exposures, but what we need is a portrait effect with a blurred background, and the small aperture of 16 is sure. We're going to put it.

And the ISO sensitivity is already the lowest 100. What can we do by increasing the shutter speed (reducing the exposure). According to the formula mentioned above, we know that the aperture from 16 to 2.8 is five steps larger (16-11-8-5.6-4-).

2. If we take a seascape on a cloudy evening, we still know that ISO 100, shutter1100, and f/ 16 are all accurate exposures, but we need a bright and layered photo. It is good to shoot a scene with a large depth of field with a small aperture of 16, but the result will be poor.

What if you can't get the required depth of field by narrowing the aperture? Let's start with lowering the shutter speed (to get more exposure). We can put it on the shelf and slow down the shutter speed according to the light at that time relative to the light at noon on a sunny day. It may be1100-1/50-1/25-113-.

3. If we shoot a basketball game in the sports official, we still know that ISO 100, shutter1100 and f/ 16 are relatively accurate exposures, but we need a bright and dynamic sports scene. The combination of slow shutter and small aperture mentioned above is not just underexposure. And the athletes in the film will be blurred.

The solution is to reduce a certain aperture and improve the shutter speed and ISO value, such as ISO400, shutter 1/800 and aperture 4. Can you calculate how much exposure this combination has increased compared with sunny day 16? Exposure is increased by two gears, shutter is decreased by three gears, and aperture is opened by four gears, which is equal to one * * * to increase exposure by three gears.

We also know that besides luminous flux, aperture also controls the depth of field. Shutter has the function of curing and informing objects and blurring slow objects; When the aperture shutter is difficult to adjust, ISO can increase the exposure, but too high ISO will bring noise to the picture and reduce the image quality.

To sum up, the exposure of the three is a trade-off, but the effects of the three are different. A photo of a street fight and a photo of a lake surging like a cloud may have the same exposure, but the two photos must use different aperture, shutter and ISO combination.

This is my personal experience. I didn't copy any books.

= = Baidu SLR Association group member "Random Bomb Years" answers for you = =