If you want a good low-cost flash that can do HSS, I'd recommend looking for a used Canon 430EXII or 580EXII (less expensive because they don't do the built-in radio RT thing), or a Godox TT350C or TT685C (which do the built-in radio Godox X thing :). Because of the multiple repeated bursts, you do reduce the amount of light coming out of the flash when you use HSS.įor more details, see Neil van Niekerk's HSS tutorial: In HSS mode, the camera and flash communicate so that the flash puts out multiple bursts, timed with the movement of the curtain gap as it sweeps across the sensor, so that the entire sensor gets lit by a bit of flash. So, the camera limits you to your maximum sync speed. When you go faster, the gap gets smaller, and one or both curtains will be covering part of the sensor when the flash burst goes off, so you'll get black/dark bars at the top and/or bottom of the frame of any image you take. At 1/200s shutter speed, that gap is just big enough to leave the entire sensor uncovered. The shutter speed control is by the size of the gap between the two curtains: the smaller the gap, the faster the shutter speed. The reason for this is because the SL1, like most dSLRs, has a focal plane shutter with a first and second curtain. The pop-up flash can't do HSS, you'd need an external hotshoe flash (aka speedlight). why is this?ġ/200s is your maximum sync speed, the fastest shutter speed you can use with flash, unless you can put the flash into HSS (high-speed sync) mode. my SL1 can take pic at 1/4000 as fastest shutter speed, but when i put my flash into the hot shoe the camera stops at 1/200, even in manual mode. We call that the X-Sync speed.Ĭan someone explain for me. When it detects a flash unit is attached and powered on, it will not allow a shutter speed faster than this maximum speed. Your camera know what is the maximum time then entire frame is exposed. You will get a dark-bar across the photo since the 2 curtain working in tandem form a moving slit across the frame If taking a non-flash photo, this is no problem.īut when taking a flash photo, since at no time is the entire sensor exposed to the light AND the flash only last 1/1000, the light reflected by the flash will not expose the entire sensor. So the second shutter is so close behind the first shutter, that at no time is the sensor fully exposed to the light. Here's what happens when you take a photo at 1/2000ġ/2000 second later, the second curtain follows behind. In either case, when taking a Flash photo, during that 1/60th of a second that the entire sensor is exposed, you Flash fires, it reflects off of your subject(s), and reflects back into the Sensor. At full power, it may only last 1/250 second. When taking a Flash photo, the amount of light output by the flash unit is controlled by how LONG it last, not how "bright" it is. The 1st curtain open, and exposes the sensor to the incoming photons.ġ/60th of a second later, the second curtain closes, stopping light from hitting the sensor You press the shutter release, and the mirror flips up exposing the sensor It can be difficult to understand, so lets looks at 2 different cases Your camera has 2 curtains covering the Sensor
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