Aperture#
Aperture is a key parameter in photography that controls the amount of light entering the camera lens. Adjusting the aperture size affects the exposure, depth of field, and image quality of the photo. Here is a detailed introduction to aperture:
1. Function of Aperture#
- Aperture controls the amount of light entering the camera lens, affecting the exposure. The amount of light directly affects the brightness of the photo. The larger the aperture, the more light enters, and the brighter the photo; the smaller the aperture, the less light enters, and the darker the photo.
- Aperture also affects the depth of field, which is the range of clear areas in the image. The larger the aperture, the shallower the depth of field and the more blurred the background; the smaller the aperture, the deeper the depth of field and the clearer the background.
2. Composition of Aperture#
- Aperture is composed of a series of adjustable aperture blades, forming a circular or nearly circular aperture opening. The size of the aperture opening determines the amount of light entering the camera.
- The size of the aperture is represented by an F-number. The smaller the F-number, the larger the aperture opening, and vice versa. For example, F2.8 represents the maximum aperture opening, while F22 represents the minimum aperture opening.
3. Aperture Size and F-number#
- The aperture size is inversely proportional to the F-number. The smaller the F-number, the larger the aperture opening, and the more light enters the camera; the larger the F-number, the smaller the aperture opening, and the less light enters the camera.
- The adjustment of aperture size is usually done in multiples of the F-number, known as an "F-stop" of the aperture.
4. Aperture and Depth of Field#
- The aperture size directly affects the depth of field in the photo. The larger the aperture, the shallower the depth of field, suitable for shooting portraits or scenes that require background blur; the smaller the aperture, the deeper the depth of field, suitable for shooting landscapes or scenes that require the entire frame to be clear.
5. Aperture Priority Mode#
- Cameras usually provide an aperture priority mode, which allows users to manually set the aperture size while the camera automatically adjusts the shutter speed to maintain correct exposure. This mode is suitable for scenes that require control of the depth of field, allowing photographers to focus on composition and aperture selection.
6. Aperture and Lens Performance#
- The size of the aperture is also related to the performance of the lens. Different lenses may exhibit different imaging quality at different aperture sizes. Generally, lenses perform best at mid-range apertures (such as F8 to F11), while they may show image distortion or lens defocus at fully open or fully closed apertures.
By understanding the function, composition, size and F-number of aperture, its relationship with depth of field, aperture priority mode, and its relationship with lens performance, photography enthusiasts can better master exposure control techniques and capture more artistic and expressive photos.
Shutter Speed#
Shutter speed is an important component in photography that controls the length of time light enters the camera. During the photography process, the opening and closing of the shutter determine whether light can enter the camera and leave an image on the photosensitive element (such as film or digital sensor). Here is a detailed introduction to shutter speed:
1. Function of Shutter Speed#
- The main function of the shutter is to control the time light enters the camera, thereby controlling the exposure time. The longer the exposure time, the longer the light enters the camera, and the brighter the image.
- Shutter speed also determines the clarity of moving objects in the photo. With a fast shutter speed, moving objects can be frozen and present clear contours; while with a slow shutter speed, moving objects show motion trails.
2. Composition of Shutter Speed#
- The shutter is composed of two parts: the shutter curtains and the shutter mechanism.
- The shutter curtains are a set of curtains located in front of the camera lens, usually including a front curtain and a rear curtain. The shutter curtains open at the beginning of the exposure and close at the end, controlling the time light enters the camera.
- The shutter mechanism is the device that controls the opening and closing of the shutter curtains, usually achieved by electromagnetic drive or mechanical mechanism.
3. Shutter Speed#
- Shutter speed is the time required for the shutter to open and close, usually expressed in seconds, such as 1/1000 second or 1 second.
- The faster the shutter speed, the shorter the exposure time, suitable for shooting high-speed motion or capturing moments; while the slower the shutter speed, the longer the exposure time, suitable for shooting night scenes or capturing motion trails.
4. Shutter Modes#
- Cameras usually provide various shutter modes, including manual mode, automatic mode, shutter priority mode, and program mode.
- In manual mode, users can adjust the shutter speed themselves and have full control over the exposure time; while in automatic mode, the camera automatically selects the appropriate shutter speed based on the environmental conditions.
- Shutter priority mode allows users to set the shutter speed, and the camera automatically adjusts the aperture size to maintain correct exposure; program mode allows the camera to automatically select the appropriate shutter speed and aperture size.
5. Shutter Delay#
- Shutter delay refers to the time interval between pressing the shutter button and the actual start of exposure. In some cases, shutter delay can help avoid camera shake and maintain image sharpness.
- Shutter delay is usually divided into two types: preset delay and custom delay. Preset delay is a built-in delay setting in the camera, while custom delay is a delay time that users can set according to their needs.
6. Shutter Vibration#
- Shutter vibration refers to the vibration generated by the movement of the shutter mechanism, which may cause image blur or distortion. This effect is more pronounced when using long exposure time or telephoto lenses.
- To reduce the impact of shutter vibration on image quality, measures such as using shutter delay, avoiding handheld shooting, using image stabilization, or stabilizing the camera can be taken.
By understanding the function, composition, speed, modes, delay, and vibration of the shutter, photography enthusiasts can better master exposure control techniques and capture clearer and more accurate photos.
7. Safe Shutter Speed#
- To capture a sharp photo without camera shake, the simplest way is to use a fast shutter speed. However, a fast shutter speed may result in underexposure.
- Therefore, after continuous shooting, photographers have come up with the theory of "the slowest shutter speed without camera shake," which is commonly known as the "safe shutter speed."
- Traditionally, the definition of a safe shutter speed is that it should not be slower than 1/focal length of the lens. For example, if you are using a 50mm lens, a shutter speed of 1/50 can capture a photo without camera shake.
- In general, when walking or capturing fast-moving subjects, set the shutter speed to around 1/250; for capturing faster freefall or moving objects, increase it to around 1/400; for capturing fast-moving subjects, set it to 1/800 or higher. (These are just suggested values)
ISO Sensitivity#
ISO sensitivity is an important parameter in photography that represents the sensitivity of the photosensitive element (such as film or digital sensor) to light. Adjusting the ISO sensitivity can affect the exposure and image quality of the photo, as well as the presence of noise and detail in the image. Here is a detailed introduction to ISO sensitivity:
1. Function of ISO Sensitivity#
- ISO sensitivity determines the sensitivity of the photosensitive element to light. The higher the ISO value, the higher the sensitivity of the photosensitive element to light, resulting in a larger exposure and a brighter photo; the lower the ISO value, the lower the sensitivity of the photosensitive element to light, resulting in a smaller exposure and a darker photo.
- Adjusting the ISO sensitivity is a way to adjust the exposure. When there is insufficient light or a faster shutter speed is needed, the ISO value can be increased to increase the exposure and obtain a correctly exposed photo.
2. Composition of ISO Sensitivity#
- ISO sensitivity is usually represented in numerical form, such as ISO 100, ISO 200, ISO 400, etc. The ISO values are multiples of each other, such as ISO 100, ISO 200, ISO 400, ISO 800, etc., with each increment doubling the sensitivity.
- Different cameras and different models of photosensitive elements may have different ISO ranges, usually starting from ISO 100 or ISO 200 and can go up to thousands or hundreds of thousands.
3. ISO Sensitivity and Noise#
- Noise refers to unwanted color or grain-like pixels in the image and is a common issue with high ISO values. When the ISO value is high, the sensitivity of the photosensitive element to light increases, resulting in an increase in noise in the image.
- To reduce the impact of noise, it is recommended to use lower ISO values for shooting or use noise reduction software in post-processing.
4. ISO Sensitivity and Detail#
- High ISO values may reduce the detail in the image, especially when shooting in low light conditions. Due to the increased noise in high ISO values, details may be lost or become blurry.
- To maintain the detail in the image, it is recommended to use lower ISO values for shooting or use higher ISO values in appropriate lighting conditions and perform noise reduction in post-processing.
5. Auto ISO Function#
- Many cameras provide an auto ISO function, which automatically adjusts the ISO value based on the shooting environment to achieve the appropriate exposure. This function simplifies exposure control, allowing photographers to focus on composition and creativity.
- Although the auto ISO function is convenient, manual adjustment of the ISO value is still necessary in some special situations, such as when controlling noise or maintaining optimal image quality.
By understanding the function, composition, relationship with noise, relationship with detail, and the auto ISO function of ISO sensitivity, photography enthusiasts can better master exposure control techniques and capture more artistic and expressive photos.
6. Recommended ISO Values for Different Situations#
① ISO 50 and below are low sensitivity
In this range, extremely smooth and delicate photos can be obtained. As long as the conditions permit and the photo can be taken clearly, it is recommended to use low sensitivity. For example, if the depth of field can be ensured, it is better to open the aperture by one stop rather than increase the ISO sensitivity.
② ISO 100-200 is medium sensitivity
In this range, it is necessary to carefully consider the purpose of the photo and the level of enlargement. If you can accept noise, medium sensitivity settings reduce the difficulty of handheld shooting and increase the safety factor for shooting in low light conditions.
③ ISO 400 and above are high sensitivity
ISO sensitivity affects photography in two aspects. Firstly, it affects the speed. Higher ISO sensitivity allows for faster shutter speeds. This can effectively avoid camera shake and capture sharp images.
Low ISO sensitivity provides three benefits for image capture: high image quality, low noise, and slow shutter speeds. For example, in scenes such as flowing water in the mountains or waterfalls, a shutter speed slower than 1/2 second may be needed to capture the dynamic flow. In sunny outdoor conditions, a larger aperture (F2.8) can be used with lower ISO to ensure that the shutter speed is within the camera's limit (1/4000 second or 1/8000 second) to reduce the chance of overexposure and achieve a softer and more diffuse depth of field effect.
For night scenes, it mainly relies on freezing the beauty in front of you by using high ISO and large aperture, such as capturing the starry sky, nighttime folk festivals, handheld city night scenes, etc., which are within the control range of high ISO.
Recommended values: ISO 100 for sunny outdoor use; ISO 200 for cloudy weather; ISO 400 or higher for indoor use.
(The higher the ISO sensitivity, the more sensitive the CMOS sensor is to light, and the less light is needed to meet the exposure requirements.)