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by Russell McMahon

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I keep seeing shoot thru an reflecting umbrellas in sizes around 33", 36", 42" and even larger. Many of the kits (stand, clamp, umbrella) I see around have the smaller size umbrellas. Strobist.com also suggests a 42".

What differences could I expect between the different size umbrellas and how might their usage / flexibility compare? Would I expect more light fall off with a larger umbrella?

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3 Answers 3

up vote 10 down vote accepted

Are you planning to shoot indoors or outdoors? Umbrellas are difficult to use outdoors as they act like a sail and it only takes a slight breeze to send your umbrella - and flashgun crashing down. You either need a serious stand weighted down, or someone holding the umbrella. Even so I'd go with the smaller size for shooting outdoor.

A larger umbrella gives a softer light - at the same distance. However it's a apparent size of the lightsource as seen from the subject that defines the softness/hardness (hence the character of the light). e.g. the sun and moon have the same apparent size, viewed from the Earth. The sun is much bigger, but at the same time further away.

Therefore a 33" umbrella at a distance of 2 meters should act very similar to a 42" umbrella at 2.5 meters. However:

  • You will receive less light from the further away brolly (i.e. bigger brollies need more powerful flashes in general). Likewise you need a bigger stand etc.

  • Having the light further away makes it easier to control flare (by ensuring the lightsource is not in frame) and gives the subject more room to move.

  • A further away lightsource gives more even lighting. Again taking the sun as an example the near and far sides of a 1 meter object are effectively at the same distance from the sun and receive the same amount of light. However if you place a lightsource 1m from the object then the far side is double the distance from the near side and receives 1/4 the light.

Finally, the difference between 33" and 42" is not that great, and 42" isn't that big in the scheme of things, so unless I was putting together a kit that was designed to be ultra mobile I'd go for the 42".

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I would point out that 42" is very big to work around. True, most pros want that size light source, but they would also opt for softboxes in most cases if presented with something that called for that big a light. I believe that without at least 300 W/S, you will be disappointed by the performance of that big an umbrella. And 300 W/S is a pretty decent size light. If you're working in the studio, again, softboxes or octabanks will probably be more to your liking. If in the field, better get some nice heavy sandbags. –  Steve Ross Sep 15 '11 at 16:07
    
in terms of umbrella size, could I expect to be somewhat more restricted in terms of how large an area at say 2 metres with the smaller umbrella? You make it sound like I wouldn't miss much with the smaller umbrella, especially for a starter. –  Mike Sep 16 '11 at 5:11
    
Something sounds wrong here: "Bigger brollies need more powerful flashes." Assuming they are made of the same material, a bigger umbrella at the same distance with the same flash should be brighter than a smaller one because it "catches" and diffuses towards the subject more of the flash (or at least never less than a smaller flash). –  feetwet Aug 26 at 20:19

A larger umbrella is more flexible - you could zoom your flash or put it closer to umbrella and get lighting equivalent to a smaller umbrella, but not vice versa.

Using a larger umbrella is similar to using a larger softbox - you can either

  • have softer, more even light at same distance, light fall-off towards edge of light beam is slower thanks to the larger light beam; or
  • you could have similar light at further distance (giving extra room for framing). Light fall-off along distance from umbrella is slower than with smaller umbrella at closer distance due to inverse square law.

The downsides of a bigger umbrella compared to a smaller one with equal design and quality are

  • higher price
  • more space needed to set up (might imply less maneuverability in tight space)
  • more power needed to light the whole umbrella
  • more volume and weight to carry
  • more receptive to wind

In studio settings, only the first three are relevant.

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Because the umbrella's shaft grows with its radius, you don't really need a wider angle in your flash. You better do have a more powerful unit, though, if you maxed out the power with the smaller umbrella. –  ysap Sep 15 '11 at 7:24
    
@ysap thanks, edited –  Imre Sep 15 '11 at 7:31
    
When you say you need more power to light a larger umbrella, would you consider an EX 430II sufficient at a range of 2 or 2.5 m? Or would I experience a lot of light fall off and be shooting at pretty slow shutter speeds? For the sake of being a bit less subjective, let's say I'm indoors, with dim indoor lighting (let's say 1/8th second f/4 or 5.6). Shooting portraits. Or would I be better off with a larger flash unit? –  Mike Sep 16 '11 at 5:09

Short Answer:

  • Larger umbrella gives softer light.
  • Larger umbrella also more likely to be blown over!

Remember:

  • As you move it further away, any light source effectively gets smaller, so a large umbrella further away behaves like a small umbrella closer to the subject.
  • If you stick your strobe right in the umbrella so it's near to the fabric, you are only using a small area of the diffusing surface, so it behaves like a small umbrella.
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