External Flash Shutter Sync settings?

[GaryK26]

Trying to figure out all about my 430EX II and have been looking at the external flash menu options on my 40D.

With Shutter Sync why not leave it on Hi-Speed all the time? (not wanting to even start contemplating 2nd curtain quite yet!).

What are the advantages of using Hi-Speed rather than 1st curtain (and visa versa)?


Thanks
Gary

 

[HoppyUK]

Trying to figure out all about my 430EX II and have been looking at the external flash menu options on my 40D.

With Shutter Sync why not leave it on Hi-Speed all the time? (not wanting to even start contemplating 2nd curtain quite yet!).

What are the advantages of using Hi-Speed rather than 1st curtain (and visa versa)?


Thanks
Gary

High speed sync gets around the problems of flash and a focal plane shutter. It changes the way the flash fires, from one big pulse to a whole stream of small multiple pulses at the amazing rate of up to 50khz. In this way, it keeps going for the full duration of the shutter cycle (google that for more info) and works at any shutter speed above max x-sync.

The downside is that most of the power is wasted, with the result that range is dramatically reduced. Just switching it on cuts the maximum power by 75%.It works superbly well, but only at short range like 2-3m.

Many people leave it permanently switched on but for some strange reason Canon has configured it so that the camera switches into HSS mode at the max x-sync speed (1/250sec on a 40D) when it's just not necessary and you might need the extra power available without it. Try it - camera in manual at 1/250sec, switch on the flash and the range scale will light up. Now switch on HSS and without doing anything else, the range will drop considerably.

With second curtain sync, just be aware that it's not the magic bullet that some people seem to think it is, and most of the time you're better off with first curtain (which is why it's the default of course).

There's a superb new book out by Syl Arena, The Speedliter's Handbook - £18 Amazon. Highly recommended.

 

[GaryK26]

Thanks Richard - you have explained it such that even I can understand (I think)

 

[HoppyUK]

Thanks Richard - you have explained it such that even I can understand (I think)

You're welcome

I forgot to mention that as you increase the shutter speed with high speed sync, the power is effectively reduced by another 50% for every stop

Which means that while it might still work at 1/8000sec shutter speed, the power at that speed is so feeble it's actually useless. I find it's really handy in the 1/250sec to 1/1000sec range though, full E-TTL control an' all.

 

[GaryK26]

So, generally speaking, HSS is best avoided.
Am I right in thinking that it becomes useful / necessary when shooting against a brightly lit background where the required shutter speed is above 1/250?
In particular, I am thinking of bride & groom portraits on a bright day, shooting into the sun.

 

[nano]

Yeh, you'll want HSS going on then just to bring the sunlight down to bearable levels via your higher shutter speed however the range your flash can manage fighting direct sunlight is really quite low.

Actually what you really really want is something like an Elinchrom Ranger then you can use that as your main light and the sun as a fill

 

[HoppyUK]

So, generally speaking, HSS is best avoided.
Am I right in thinking that it becomes useful / necessary when shooting against a brightly lit background where the required shutter speed is above 1/250?
In particular, I am thinking of bride & groom portraits on a bright day, shooting into the sun.

Well not avoided exactly. When you need it, you need it, and frankly most of the time I'd far rather have an E-TTL enabled gun with HSS than an Elinchrom Ranger (which has neither HSS nor E-TTL).

Your example of the back-lit bride and groom is a perfect example when the high ambient light will naturally push your shutter speed above the x-sync ceiling. E-TTL works out the exposure remarkably well, or is easily adjusted with +/- compensation if it doesn't, and the gun switches seamlessly in and out of HSS as and when necessary.

So long as you're in range, and luckily fill-in flash actually needs surprisingly little power to make a big difference, it's point and squirt simple and you can concentrate on the subject.