Difference between high speed sync flash and regular fill flash?
Hi guys, I'm just wondering what is the difference between regular fill flash and high speed sync flash for my Canon 430EX? Can someone tell me in which situation I would HSSF and in which situation I would use fill flash? Thanks!..

Comments (8)


I don't have one of those Canons but the answer is that the high speed is what you use when a high shutter speed is needed. Usually, flash fires at low shutter speeds like 1/50th or so to be certain the shutter is fully open as the flash lights up the subject..

As for fill in, you use it for shots into the light. The classic is a portrait with the face in shadow but the sun lighting up the hair from behind the subject. So the face is in shadow and the weak fill-in flash just lights up the face. Of course you can also use it in other situations where the contrast between light and shade is too extreme. So mostly you use it to lighten shadows..

Years ago we did it all manually by sorting out the exposure for the scene and then adding a weak / diffused flash (hankerchief or cigarette paper over the flash generally) and picking the shutter speed etc carefully and then doing sums involving the distance from flash to subject and the aperture - all good fun... Nowadays the thing usually does it all for you..

Hope this helps..

Regards, David..

Comment #1

Don't have the Canon 430EX but it works much the same way with all speedlights..

All cams have a max synch speed with flash. The figure varies between 1/180th and 1/500th. If you want to shoot with a higher shutter speed you have to use high speed sync. The downside is that most flashes have much less power in high speed sync..

You only really need it when you have movement which is part lit by natural light and which might be otherwise be blurred by movement. A normal flash exposure is something like 1/2000 and thus stops the action by itself if it is the only light source..

Chris Elliott.

*Nikon* D Eighty + Fifty - Other equipment in Profile.


Comment #2

Most digital single lens reflex cameras are designed so that there is a moving "window" that passes over the sensor. If the window is wide, there's a time during this passing over process where the entire sensor is behind the open window. A flash can go off at this point, and all the light will hit the sensor..

At faster speeds, the window is narrower, so that only part of the sensor is exposed at any one time, but all gets exposed during the time the window passes over the entire sensor..

With high speed sync, the flash pulses several times, so that the light hits the first part of the sensor, the middle part and the last part. The number of pulses varies with the speed of the moving window..

Because the flash is pulsing instead of putting out one blast of light, the power available for each pulse is less than the big blast..

EXPERIMENT: you can use normal flash and a shutter speed higher than sync speed, and you'll see part of the image cut off. The higher the shutter speed, the more of the image is cut off..

WHEN: If you want to use a combination shutter speed and aperture in order to properly expose a background and that shutter speed is higher than sync speed, you need high speed sync..

For example, Bill is standing under a tree, and the background is a sunlit field..

You want flash to brighten up Bill..

The background requires 1/500 at f8., but your max sync speed is 1/200. Set highspeed sync at 1/500, and the picture will be properly exposed in the background..


Comment #3

A model answer! Well done!.

Chris Elliott.

*Nikon* D Eighty + Fifty - Other equipment in Profile.


Comment #4

Thanks for the responses guys. For daytime situations, would it be safe and advisable to just set my flash to high speed sync? This way I won't forget to it when the opportunity is there to take the shot? Only in low light situations would I turn off HSSF?..

Comment #5

Re>would it be safe and advisable to just set my flash to high speed sync? <.

Should work fine, the only problem being lack of total flash power so you might find yourself without enough flash power to take care of the distance you are shooting at..


Comment #6

I think that you have missed a point here. There are two types of flash, regular flash and fill flash..

With regular flash the flash provides the main source of illumination. The camera controls the exposure by controlling the duration of the flash. Under certain circumstances (explained by the other posters) the flash has to be set to high speed sync. In general it is true to say that the aperture and shutter speeds have no effect on the exposure of the main subject in this mode, although they do affect background areas..

With fill flash the main illumination is provided by non-flash lighting, e.g. daylight, and the flash is used to fill in the shadows. The camera sets the exposure for the ambient lighting..

Canon cameras will use fill flash if you set the mode to Av or Tv. If you use manual or auto mode the camera will use regular flash. I cannot remember what happens with scene modes..

You wouldn't normally have the flash set to High Speed Sync except in situations where you want to use a high shutter speed.Chris R..

Comment #7

When you set HSS on your flash, it will show you the range on the back, just like using regular flash. You will notice that your effective flash range is seriously lower. Also, the HSS function can literally fry the flash if used too much. Then there is the part about it sucking batteries pretty fast too..

I wouldn't just set it to HSS and leave it there. I don't have a 430 flash, but on the 580 series it only takes a second to turn it on. I save it for when I really do need it..

Crime Scene PhotographyA small gallery of personal work:

Comment #8

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