420EX Very Bright Light, Fill Flash & High Speed Sync

[bennyboy]

I understand that high speed sync results in significantly lower flash power,

with having recently been shooting at an outdoor event in extremely bright

light, and needing to use fill, I found I had to use high speed sync in order to

not significantly overexpose my shots (and retain a shallow enough DOF for some

of the photos) - however, my 420EX doesnt seem to have enough oomf to

satisfactorily fill subjects who are even a few meters away. Is it time I

upgraded to a 550 or 580, or should I be looking at my technique?

[jim_larson1]

The 550EX and 580EX have about one stop more power than the 420EX/430EX.

 

BTW: In bright light, the camera will attempt AFFR, Auto Fill Reduction. Have you tried flash exposure compensation?

[jim_larson1]

The 550EX and 580EX have about one stop more power than the 420EX/430EX.

 

BTW: In bright light, the camera will attempt AFFR, Auto Fill Reduction. Have you tried flash exposure compensation?

[bennyboy]

I was shooting with about 1 stop of EC but didnt have any FEC dialed in.

[lad_lueck]

What camera are you using, and what AE mode, and what shot technique?

 

The camera should expose correctly unless your exposure needs more light than the flash can provide (not your problem, here).

[bob jr.]

Ben, probably technique here. Dial in a higher Flash Exposure Compensation.

[michael_madio]

The problem is not the flash power but the limited x-sync speed of the camera. Use the camera on manual, select the lowest ISO setting/film, set the shutter speed to x-sync (this varies with each camera ... you will have to check the manual for yours), set flash-exposure-compensation to -1 stop, and adjust aperture according to the meter. A simpler solution is to find open shade.

[jeffcallen]

High sync speeds and distances more than 2 meters may require much more "power", like 2 or more flashes, I've used 2 550EX's to do this, and it works well. Normal guide-number/distance calculations didn't seem to work with HS sync, but there may be a new equation somebody can teach me - other than shoot and test. People above are right that canon tries to think for you and may underexpose, but I've found that when I tried an extra flash, I had enough power.

[eric merrill]

420ez or 430ex? To my knowledge, there's not a 420ex.

 

I just reviewed the settings from a session I did recently using a 430ex. Shot mostly at f/3.5-f/4. ISO 100. Shutter speed ranged from 1/200 to 1/2000. Flash compensation varied. I don't see anything in the exif data that shows me what my compensation was for any particular shot. Based on what I usually do, it was anywhere from -1 1/3 to +1

 

All from about a couple meters away from the main subject, using a Demb reflector (but not the diffuser part):

 

http://www.dembflashdiffusers.com/

 

The point here is that it wasn't even straight on flash. I could have gotten even more fill from the 430ex, if necessary. I'd play around some more before shelling out more money for new equipment.

 

 

Eric

[jimstrutz]

Eric, of course there is a 420EX. It was replaced by the 430EX only a year or two ago. The 420EZ and 430EZ don't do FP (high speed sync), the 420EX and 430EX do.

[PuppyDigs]

Lots of possiblies to try in the above responses. Here's one nobody hit on. In bright light, E-

TTL and E-TTL II reduce flash exposure by about 2 stops. This feature is called auto fill flash

reduction. Many EOS bodies have a custom function to disable auto fill flash reduction and

allow a full exposure blast of light. On the 5D it's CF 14.1 (Flash averaging/disable auto fill

flash reduction). The 20D and 10D have similar CFs (some film bodies as well.) Of course

you'll have to manually dial in FEC if it's too bright for your taste.

[Ken Katz]

Keep in mind that unless you turn off the feature (via custom functions), in bright light, the camera will automatically apply fill flash exposure reduction, so that any amount you add (or subtract) is on top of what the camera already did.

 

In bright light, using both high speed sync and any flash diffuser or reflector is eating up a lot of available power, so I would not recomend any flash diffuser for fill flash in bright light (can be useful though in shade).

 

Using hi speed sync with my 550EX in bright light, I find I can get effective fill at no more than 15 feet away. I would think that the 420EX would have an effective range of about 10 feet. You need to wait until the flash has fully recycled since you are probably using max power for each flash.

[bennyboy]

Thanks folks, to answer some questions above:

 

Shooting with a 5D, evaluative metering, not sure about the 'shot technique' question :)

 

I wasn't able to find any suitable shade as I was taking candid shots at an event (2006 War and Peace show in the UK - google it). There're a couple of photos in my portfolio from it.

 

I guess my answer is to turn off the auto fill flash reduction in future - thanks everyone. Although I will start saving for a more powerful flash too as.

[bennyboy]

PS, at ISO 100 and f/8 I was still getting shutter speeds of 1/1250.

[awindsor]

Ben,

 

Flash can be a bit counterintuitive. Here is another solution that no-one has hit on. Increase the ISO. You of course have to then make shutter speed twice as fast but presto your flash is 1.4x as powerful. OK it won't actually be more powerful but it will contibute more light to the exposure - its guide number will increase. Similarly increasing the shutter speed and opening up the lens will make your flash contribute more.

 

The only things that matters for the flash exposure are the ISO and the aperture. The shutter speed is irrelevant even in FP (actually it is relevant to the amount of battery drain but not to the exposure).

[bennyboy]

Thanks Alistair, I'll keep that in mind - it does seem very counter intuitive, but perfectly logical.

[lad_lueck]

Ben, if you are using evaluative metering, bright sky can play havoc with outdoor exposures. Use center-weighted average, or use spot on the bright and dark clothing to determine your manual exposure.

[bennyboy]

Manual and spot metering didn't really lend themselves to the fast moving nature of much of the shooting, but I'll keep that in mind.

[mark u]

The maximum flash range in HSS mode doesn't obey the normal guide number rules, because the power output of the flash is roughly constant, spread over a period that covers the entire shutter curtain movements. Remember that above X sync, the shutter curtains only expose a moving slit across the sensor/film that is narrower the faster the shutter speed set. The consequence is that for a given ambient exposure the flash range is the same - regardless of whether you shoot 1/500th at f/8 or 1/2000th at f/4. Upping the ISO doesn't help either - to get the ambient exposure correct, you need a shorter shutter speed at a given aperture, negating the gain when you are using the flash as fill (and if the flash is the dominant source of light, you are best to use X sync for greater effective power output). Think of HSS mode as equivalent to illuminating your subject with a tungsten lamp - all it does is alter the balance between the ambient and artificial light by an amount that reflects the power of the lamp. If the lamp isn't powerful enough, you can only use a more powerful lamp, or place it closer to the subject, to change the lighting ratio.

 

Because of the inverse square law, you will need something MUCH more powerful if you wish to light subjects a few meters away (adding a 580EX won't cut it either) - perhaps one of the most effective solutions is to use the power of the sun with large reflector boards.

[mark u]

For completeness, I should point out that adjusting FEC or negating auto fill flash reduction or using a manual power setting are NOT going to increase the maximum range of the flash in HSS mode. The maximum power is the maximum power - you can't have more than that. Bear in mind that to double the range, you'd need 4 times the power - although you can use HSS with wireless flash. Perhaps renting some location lighting might be an alternative to reflectors - but flash is likely to be totally inadequate. The 580EX gives a range of 15 meters at f/1.4 and 1/250th with a full frame 50mm angle of view in HSS mode according to Canon. Even at full 105mm zoom, you would have a maximum range of ~15 x 58 / 42 / 11 - or just 2 metres in your bright conditions - perhaps a little more if you allow a lower fill ratio in your results. You're between a rock and a hard place, because you'd need to be shooting at very narrow apertures for max X sync, also dramatically cutting the flash range (and perhaps introducing other undesirable effects, such as sharper backgrounds, diffraction etc.).

[awindsor]

Bugger. You are right.