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Saturday, March 20, 2010

Flash : Dramatic lighting in daylight

Today I did some tests to see what working distance I could get outdoors during the day with one flash and an under-exposed background .
I set the camera up in manual mode and metered the lighting at iso 200 , 1/200th and F16 . Occasionally the meter jumped to show that I needed F18 but that was due to the bright cloud .

And of course with me standing in the shade this is what it looks like without flash .

[ It has been pointed out that there is a difference in the background exposure - this is due to the clouds moving and the sun appearing occasionally , these things are never simple :) ]

Then we add direct flash .

And then I added the diffuser dome ....

There is very little difference with direct flash and the diffuser dome - the face of the dome is the same size as the flash head and provides the same amount of diffusion outdoors besides wasting a lot of energy on nothing by firing the flash at a much wider angle than the lens is taking in .

I haven't yet seen a logical reason to use the diffuser dome outdoors - all it does is waste power without adding anything to the picture .
I also tried a few shots with my large bounce card at an angle and realistically all it does is shift the angle of the flash a bit to the side and waste power . If you are close enough to the subject this change in angle can look quite dramatic but for practical photography it makes very little difference .

Now on to the 'dramatic' aspect of the experiment . Some people will dial in "-1.7" on the ambient [ any light that isn't flash ] exposure to make the background darker and the subject stand out . I was in manual mode and dialed in an aperture of F29 which showed me "-1.7" on the exposure scale of my meter .

Now at the aperture of F16 the flash was already telling me I had about 4 m working distance at best . By dialing in -1.7 I am also making it harder for the flash - smaller apertures mean it needs more power to get the same amount of exposure on the subject . [ A smaller aperture lets in much less light - ambient or flash - and so while darkening the background also requires more flash power for the subject ] .
At F29 the flash head was telling me I had 2.2 metres working distance at 50mm and 0.8 metres with the diffuser dome on . Since we are under-exposing the ambient by so much the flash will need to light the subject on its own so we aren't just using 'fill-flash' here . 
If we only have 0.8m with the diffuser dome on then tilting the flash head and using the bounce card would waste more power and render that approach useless basically .
I went to plan-B and took the flash off the camera using an SC-17 flash cord .

This was held in one hand facing directly at the subject and provides the very different look of off-camera flash along with the dramatic side lighting and dark background which makes the picture look very different to the first picture with flash .
 These images are all straight out of the camera with no processing or adjustments to the flash [ TTL/BL mode ] and obviously could look better with some adjustments and a prettier subject !

We are saving a lot of power with direct flash and hence maintaining our working distance compared to diffusers . We would need more flash power if we wanted to diffuse the light as well - or darker ambient lighting - then we could open the aperture up a bit more to help the flash . Late afternoon or dusk would provide ideal conditions to be able to have a dark sky and a wide enough aperture for the flash to be strong enough to also be diffused for even more professional results .


  1. I agree on using the flash diffuser outdoor is a waste of power... And even for me, during events in halls and large room I too feel that using the diffuser is a waste of power because the area of light coming out is still the same.. I get less burst and lower number of shots with the diffuser, and sometimes a lot less.
    Worst, not enough power at all!

    Nice post.. Thanks a lot.

  2. Yeah , it obviously wastes a bit of power [ besides the way it spreads the light ] because in TTL/BL the program increases flash output when the little button on the flash head is pushed down - an attempt to compensate for the power loss caused by the diffuser dome being fitted .
    Many people use it because they see the [misinformed ]pro's using it .

  3. "misinformed pros using it?" sounds to me like you guys just don't know how and when to properly use it. The reason most "misinformed pros" use it is to close the distance without bottoming out the shadows and to prevent irregularities in skin from destroying an image. "Pros" as you would call them,usually take several sets of batteries so no "pro" even worries about power consumption. I really hope to god amateurs don't use this article or posts as reference. Sheesh.

  4. Well David maybe you can explain how wasting so much power with a diffuser dome does any different to not using the diffuser dome outdoors?
    Diffusion is proportional to the size of the light source which is the same when the diffuser dome is on so all it does is waste energy when there's nothing to bounce off - yeah , carry more batteries and speed up global warming if you like - if you don't have brains you have to use brawn I suppose .