Learning Flash Stuff

[snerd]

So I dove into flash tonight! I have a 430EXII and had no idea how to use it. So I was trying different apertures, ISO's and shutter speeds using various items around the house. The mysteries slowly started to unravel and what I wound up learning is that you just mount the thing, use the camera to set it with auto zoom, and shoot away!! My better shots (not saying much) were set at mostly what I would use in non-flash shooting. Camera in Manual mode, ISO 100, a 100mm 2.8L macro at 3.2 - 4.5, ss's at 250, and the flash unit pretty much took care of everything! I did set WB to flash after trying them all. Just looked the closest. So, something easy this way came tonight! (for a change!) I'm sure I need to learn the other detailed settings on it, and their uses. But I feel a lot better about using flash tonight!

I guess what confuses me the most is that at ss of 250 it wasn't even in the ballpark as far as exposure. So I couldn't go my my camera meter, just take the shot and it was plenty bright! This normal? I also couldn't get it above 250 either.

 

[ShaneF]

for general use max sync speed is 1/250 but its just a suggestion not a rule..

This might explain things better

http://www.exposureguide.com/high-speed-sync-flash.htm
Strobist
Strobist: Know Your Sync

 

[tirediron]

Yes, absolutely normal. Your camera is controlling the exposure by reading the return from the flash and adjusting on the fly. The ambient light really has very little effect on the exposure at all.

 

[KmH]

Speedliter's Handbook: Learning to Craft Light with Canon Speedlites
Understanding Flash Photography: How to Shoot Great Photographs Using Electronic Flash

1/200 or 1/250 is the flash x-sync limit, because that is the fastest shutter speed that has both shutter curtains fully open during an exposure.

Canon calls the 2 shutter curtains the first and second curtains, while Nikon calls them front and rear.

By default, most cameras are set to sync the flash to fire when the first/front shutter curtain is fully open - front/first curtain sync.
When first curtain sync is set, if anything in the scene moves during the exposure a 'ghost' trail will precede the direction of motion, because the movement happens after the flash has fired.
Images like that don't look very natural, because the ghosting does not support the notion of motion.

Setting the camera to rear/second curtain sync the flash fires just before the rear/second curtain starts to close and end the exposure. - second/rear curtain sync.
When rear curtain sync is set, if anything in the scene moves during the exposure a 'ghost' trail will trail the direction of motion, because the movement happens before the flash has fired.
Ghosting that trails looks more natural, because the ghosting does support the notion of motion.

At shutter speeds faster than the cameras x-sync speed, one or both shutter curtains block a portion of the image sensor during an exposure, even if flash isn't used.
In other words the 2 shutter curtains form a slit. The faster the shutter speed, the narrower the sit becomes.

Flash can be done at those higher shutter speeds, but the flash unit has to fire multiple times during the exposure.
Canon calls this flash mode High Speed Sync, or HSS. Nikon calls it Auto-FP sync.

Not all DSLRs or flash units can do high speed sync, particularly entry-level grade cameras and flash units.

Flash units take time to re-cycle the main flash capacitor from a full power flash - 2 seconds and longer depending on the flash unit and how it is powered.
Since high speed sync requires multiple flashes per exposure and the shutter speed is faster than 1/200 or so, there isn't time to re-cycle the flash during an exposure time shorter than the camera's x-sync speed.

So high speed sync has to be done using well less than full power for each of the multiple flashes.
If 2 flashes are needed during the exposure each flash has to be made at 1/2 of full power.
If 4 flashes are needed during the exposure each flash has to be made at 1/4 of full power.

Because of the inverse square law, if the power is reduced by 1/2, only 1/4 as much light reaches the subject with each of the 2 flashes. At 1/4 power, only 1/16 as much light reaches the subject with each of the 4 flashes.

Flash units need to be much more powerful to be used on high speed sync mode so they can deliver enough light when they flash.
The camera and flash unit electronics also need to be more sophisticated to make high speed sync happen, which is why most entry-level cameras and flash units are not high speed sync capable.

 

[snerd]

Very informative, thanks!

 

[table1349]

For a Canon strobe user this is a must.
Flash Photography with Canon EOS Cameras - Part I.
Flash Photography with Canon EOS Cameras - Part II.
Flash Photography with Canon EOS Cameras - Part III.

 

[Gavjenks]

Yes, you are using ETTL flash, which is basically the flash equivalent of the green box / full auto mode on your camera's exposure settings.

It is useful in a pinch or when starting out, but just like your exposure settings, you can and will get better results from actually fully understanding how flash works and what the settings should be yourself, such that you can decide when to alter them to fit your creative needs, rather than the camera's assumptions about your needs.

You may still use ETTL later after fully understanding flash, because it is sometimes the best choice, just like full auto may occasionally be. But when and if you do, it should be because you made the informed decision that auto flash was the best choice (for instance, in a fast-paced environment with wildly varying lighting conditions as you move around a lot, like a carnival at night or a theatrical convention hall).

 

[KmH]

FWIW
E-TTL is Canon's through the lens flash exposure system. (E = Evaluative)

iTTL is Nikon's current through the lens flash exposure system, which was preceded by Nikon's D-TTL. (i = Intelligent)

 

[Derrel]

Canon has a nice, pamphlet-length, on-line QuickGuide to the 430 EX-II flash located here:

http://www.learn.usa.canon.com/app/pdfs/quickguides/CDLC_Speedlite430EXII_QuickGuide.pdf

 

[snerd]

[SIZE=-1]1) My camera already has a built-in flash. Do I need an external one? If so, what kind?

[/SIZE]

[SIZE=-1]This question crops up all the time on discussion forums, much to the irritation of oldtimers. And their irritation usually arises for two simple reasons. First, they’re grumpy cantankerous curmudgeons and second, the question is sort of meaningless without knowing what your photographic requirements and interests are.[/SIZE]
​

Thanks all for not being cantankerous!! LOL!!

 

[snerd]

Took some good indoor flash shots today, getting the hang of it. I also want to learn how to use for fill light outdoors. The information and members here are invaluable! Thank you all!!