Brief introduction of flash photography

Lead: We all know that photography is inseparable from light, and only when there is light can there be a shadow. So photography is an industry that paints with light. In the case of unsatisfactory lighting conditions, in order to achieve better shooting results, we will choose to supplement the light of the scene environment with flash, and even use multiple flash lights to create a light source when necessary to create an ideal shooting environment with multiple lights. Let's take a look at an indispensable accessory in photography-flash.

First, get to know flash.

As an important accessory of photography, I believe everyone has touched it to a certain extent, but usually the first time we touch the flash, it is because of the lack of light at the scene, and then we use the flash to make up the light. Flash is an artificial light source. When it needs to be used with field light, it will involve a series of problems such as brightness, exposure, light level and light shape. Flash, called flash in English, is one of the ways to increase exposure. Using a flash in a dim scene helps to make the scene brighter.

Shoot the scene with a flash.

Second, the flash type

Flash can be roughly divided into three categories: built-in viewing lamp, hot shoe flash and external flash.

1。 The built-in flash is a small flash that comes with the camera. Used for small-scale fill light, as an auxiliary flash.

2。 Hot shoe flash is a kind of external small flash, which has a wider application range, a slightly larger flash index, richer functions and is easy to carry.

3。 External flash, large flash system, external power supply, high-power flash, with portable electric box. Mostly used for commercial product shooting, commercial portrait shooting and large-scale photo shooting.

Outdoor portrait shooting scene

Third, all kinds of flash usage

1。 Hot shoe flash

Hot shoe flash should be the most commonly used flash for most photographers. Then let's take a look at the requirements of a good hot shoe flash: automatic zoom of lamp head, automatic change of ISO, adjustment of exposure compensation body, TTL flash metering, high-speed synchronous flash, radio signal flash, master-slave flash, and frequency flash with continuous flash at intervals. Satisfying these conditions, we can easily get the desired effect in actual shooting. Here I recommend 430EX III-RT and 600EX-RT to Canon users, and Nikon users can also choose SB-9 10.

Hot shoe type

From the above picture, we can easily find that hot shoes have single contact, double contact or multi-contact. The functions of contacts are different, and naturally they are different. Simply put, the more versatile the network, the bigger it will be. For example, TTL flash must have a special touch point to sense, while the flash with only one touch point only has flashing function, and the output flow of the flash needs to be controlled independently. And TTL is the abbreviation of (through the lens), which can be translated as "light passes through the lens". In fact, this metering determines the output of the flash in the field of view seen by the viewfinder, and the probability of failure is extremely low. This TTL metering method will be more accurate, and it is the mainstream flash metering method at present.

Photometric determination of flash lamp

The initial flash cannot change the output, and every flash is full output. If the distance between the subject and the camera changes, it is necessary to adjust the aperture size to control the acceptance of the flash, so as to obtain appropriate exposure. Until then, there appeared an automatic flash with an external photometric original, and the output of the flash can be controlled according to the light receiving degree of the main body. As for the method of controlling the light quantity of the flash, it is to control the on and off time of the flash. The flash time is only between11000-1/0000 seconds. According to Canon's official big data, ordinary flash is about 1.8 milliseconds, and high-speed flash is about 2.3 milliseconds.

When the shutter is opened, the flash will output at the same time. When the photometry module thinks that the amount of light reflected by the object is enough, it will stop the flash output in the middle of exposure (when the shutter is still open). The exposure of the subject depends on the flash, mainly depending on the time when the shutter is opened. It should be noted here that the automatic flash also has the problem of external metering of the camera. If the lens is equipped with a filter, it will affect the accuracy of the flash output. After TTL flash appeared, because we can get data such as aperture and subject brightness through lens photometry, we can truly reflect the amount of light needed, control the flash time more accurately, and save the trouble of calculating aperture and distance in the past. Modern flashlights can even achieve zoom linkage, which is helpful to adjust the irradiation range and make the power supply more effectively used and not wasted.

The flashing process of TTL flash is a secondary flashing process. The first time is a flash, and the light shines on the subject and reflects back into the camera. According to the reflected light, the photosensitive element of the camera outputs a command to the flash, and the flash adjusts the output intensity to flash again. This time is the real exposure. Because the interval between two flashes is very short, most people don't feel the second flash. It should be noted here that, like automatic metering and exposure, TTL flash only provides normal exposure, which can still be changed by flash compensation if necessary. General flash has 1/3 EV adjustment. Therefore, TTL is best used as a reference index for normal exposure and will be changed when necessary. On the other hand, when we set the camera to automatic exposure mode (such as P or Auto), the camera often fixes the aperture and shutter at a certain value. If you want to control the depth of field, the dynamic performance of the subject and the brightness of the background, you need to use the manual exposure mode.

2。 External hot shoe flash

External hot shoe flash has strong applicability and is favored by many photographers. The use and shooting skills of this flash are very diverse. Let's take a look at the characteristics of this flash:

① The flash index is large, generally around 18-60, which is suitable for shooting more scenes.

② Flexible use and enhanced operability. The operation is more flexible, and it can control the output of flash quantity and change the direction of flash. Even some advanced flash lamps can be operated by wireless remote control outside the machine.

Canon 5D with external hot shoe flash

First of all, the basic control modes of the flash are divided into manual M mode, automatic A mode and TTL mode.

① Manual mode: The output light of the flash is completely controlled by manual operation. If the subject does not move, this constant output light phase provides a very stable light source, so it is suitable for fixed environments such as photo studios.

② Automatic A-block mode: The flash calculates the amount of light to be output according to the measurement of the scene ambient light darkness by the light sensor on the flash body and the data of the body (focal length, aperture and ISO). Therefore, in the process of calculating the output light of the flash, the effect of lens plus filter cannot be added. In addition, the flash sensor must face the main body, so it is only suitable for "direct shooting" and not suitable for adding accessories.

③ TTL mode: The calculation of the output light quantity of the flash depends on the photometry of the camera body, so it can also count the change effect of the light quantity after the lens is added with a filter. The advantage of TTL is that it is flexible in a changing environment, but in a fixed environment, a slight deviation will also lead to inconsistent output, so it is not suitable for shooting scenes such as photo studios.

The irradiation range of flash and the use of jumping flash;

The effect of using flash at different focal lengths

From the picture, we can see that the flash can't find all the parts in the picture very evenly. The light is relatively uniform at the wide-angle end of 24mm, and slightly stiff at the telephoto end of 105 mm, so we should control the main body or main object in the main working area of the flash according to different focal lengths to obtain good illumination.

Let's take a look at the contrast effect of flash plus soft mask and diffuser:

Shooting effect when using diffuser and soft mask

As can be seen from the figure, when the focal length is 14mm, the light is uniform, but the overall brightness of the picture is insufficient, so it is necessary to increase the flash compensation to improve the illumination brightness during shooting. When the focal length is 24mm, the light will be softer when the flash is used with the soft mask, which is more suitable for shooting female characters or children.

The use and effect of "jumping flash";

Jumping flash is a commonly used shooting technique, that is, the light hits the ceiling above the head or the surrounding wall, and then shines on the subject after being reflected by the wall, so that the light will become softer and get more natural light supplement. When using the flash, even if the flash lights up at a nearly vertical angle, there is still diffuse light directly on the subject, and then a more obvious shadow will be formed behind the subject. In order to eliminate this influence, a shading sheet made of opaque material or black plastic foam template can be added to the lamp holder of the flash lamp to prevent diffused light from shining on the subject.

Shows an example of using flash jump technology.

Fourth, the role of the flash.

1。 Field fill light

The main function of the flash is to illuminate the scene in the case of insufficient light and obtain the correctly exposed image. Most digital cameras have an automatic flash option. When there is insufficient light in the scene, the flash will automatically pop up and flash.

2。 Increase shutter speed

Many times we use flash, not because the light is not enough to expose correctly, but to improve the shutter speed to achieve the purpose of curing dynamic images. For example, if you want to take pictures of water droplets or moving portraits, if you expose them according to ordinary photometric values, the images will be blurred and not clear enough, and these images can be solidified by flash.

3。 Increase depth of field

When a flash is used. We can reduce the aperture accordingly. Effectively increase the depth of field.

4。 Highlight potential customers

When the flash is shot, the shutter speed is high, and the background outside the projection range of the flash cannot be expressed due to insufficient exposure, while the foreground can be correctly exposed due to flash illumination, thus highlighting the foreground and eliminating background interference.

The use of flash can effectively highlight the shooting prospect.

5。 Reduce contrast

Another common use of flash lamps is backlighting. When shooting, it is common that the contrast of light in the scene is too large (such as portraits in backlight). Due to the limited brightness range that the sensor can display, some image details will be lost in the scene with excessive contrast, whether exposed to light or darkness. In this case, the best way is to fill the light in the dark to reduce the contrast of the picture. Of course, you can also reduce the light in the bright part.

Contrast Effect in Backlight Shooting

6。 Adjust color temperature

When photographed under electric light, photos tend to appear warm yellow and red tones, because the color temperature in tungsten lamp is low, and the flash can effectively adjust the color temperature, thus correctly restoring the color of the subject.