What type of SLR overhead flash should I buy in 500 yuan?

Are you going to use it on that machine? 5D and 6D can use the same lamp, but a7 can't match those two lamps, so we have to buy them separately. Canon has many domestic products to choose from, and this price is no problem. Yongnuo, Wolong and Yin Yan have many models to choose from, but Sony's domestic products are few (although they are available in all product lines).

Reference models: Yongnuo YN560IV, YN585EX (recommended), Shenniu TT350S, TT600S, Stander DF-800, Pinse X800C, Jaguar TR-985C (recommended) and Wolong 800-RT (recommended).

Finally, popular science:

The English scientific name of flashlight is flashlight. Flash is also one of the ways to enhance exposure, especially in dim places, which helps to make the scenery brighter.

The Chinese full name is "electronic flash", also known as high-speed flash. The electronic flash lamp stores high-voltage electricity through the capacitor, and the pulse triggers the flash tube to discharge, thus completing the instantaneous flash. The color temperature of the usual electronic flash is about 5500K, which is close to the color temperature in the sunlight during the day. Its luminescent property belongs to cold light type, which is suitable for shooting objects that are afraid of heat.

Flashlights can be roughly divided into three categories, and their functions and performances are different according to different types.

1, built-in flash, using the built-in flash will cause a lot of power consumption of the camera, and the built-in flash does not support various advanced functions of the flash.

2, external flash, external flash is generally located at the top of the camera fuselage, some high-end external flash also provides a variety of advanced functions.

3, handle flash, handle flash is often used in photo studios, photo studios, wedding photography studios and other professional places.

operating circuit

Ordinary flash refers to a flash whose output energy is not adjustable, that is, the nominal flash index GN of the flash is a constant value.

The circuit consists of four parts: the oscillating boosting part, the rectifying charging part, the voltage indicating part and the pulse-triggered flashing part. When the power supply is turned on, intermittent oscillation is formed by using the switching characteristics of transistor V 1, so that the primary of T 1 obtains AC voltage, and the secondary of T 1 obtains AC voltage greater than 300 V. The AC voltage is converted into DC voltage after half-wave rectification by diode D 1, which charges the main capacitor C2 and the trigger capacitor C3 to store energy. When the voltage is charged to about 70% of the rated voltage, the neon lamp (Ne) in the indicating circuit lights up, indicating that the flash lamp is in a normal flashing waiting state. When the button AN is pressed, the trigger circuit (composed of R3, C3, T2 and Xe) generates a pulse voltage, and an instantaneous high voltage (about 10kV) pulse is induced in the secondary of the Xe flash tube, and the nitrogen in the Xe flash tube is ionized and turned on through the trigger electrode of the XE flash tube, and the electric energy stored in the capacitor is instantaneously discharged through the flash tube and converted into light energy, thus completing the flash.

The working principle of the built-in flash of the camera is the same as above. When the brightness of the external scene is insufficient, the camera's metering system sends out weak light information, and at this time, the camera manually or automatically turns on the flash circuit to charge the flash. Some cameras also have systems that automatically control the amount of flash (automatic dimming flash) to obtain more accurate exposure.

Working theory

When the flash is fully charged, the synchronous contact of the flash on the camera is connected to the flash circuit. During the flash, the light emitted from the flash illuminates the subject, reflects from the subject and enters the camera (for exposure) and the flash metering element. The photometric element quickly converts the light energy into an electrical signal and inputs it into the integration circuit, and then the integration circuit outputs an electrical signal proportional to the light value of the flash lamp; When the light value of the flash lamp meets the requirements of proper exposure, the output electric signal of the integration circuit causes the control circuit to trigger the flash stop circuit, thereby turning off the flash lamp. Because the continuous flash time of the flash lamp is very short, the flash metering element used must be a photosensitive element with fast response ability to adjust the light. According to the different circuit structures, the control modes of automatic dimming flash can be divided into parallel connection and series connection. The discharge tube V is connected in parallel at both ends of the main flash tube Xe. The ignition circuit of the main flash tube is the same as that of the ordinary type. When the luminous quantity of the main flash lamp reaches a certain reference value, it is received by the photometric element, and the integrating circuit and the control circuit contact with the discharge tube, and the un-discharged energy in the main control mode is immediately released, so that the main flash lamp is extinguished. The parallel automatic dimming flash lamp circuit has the advantages of simple structure, low price and wide application. However, because it discharges all the remaining energy of the main capacitor every time, it takes a long time to charge and consumes a lot of battery. The series control mode is that the semiconductor switching element thyristor rectifier SCR is connected in series with the main flash lamp. When the light output by the main flash tube meets the requirements of proper exposure, the thyristor rectifier SCR automatically cuts off the discharge circuit, so that the main flash tube is extinguished immediately and automatic dimming control is realized. The advantage of series control mode is that the residual energy in the main capacitor is still retained, so the charging time can be shortened, and the battery consumption can be reduced accordingly, which is beneficial to rapid flash charging and recycling. Disadvantages are complex circuit and high cost.