A Site for Photographers by Photographers

Community > Forums > Lighting Equipment and Techniques > flash depth when using an...

Featured Equipment Deals

Basic Printing with Lightroom (Video Tutorial) Read More

Basic Printing with Lightroom (Video Tutorial)

Learn to print your images directly from within Lightroom. This video tutorial covers the basic settings (page borders, watermarking, print resolution, and paper and printer preferences) for creating...

Latest Equipment Articles

4 Outdoor & Adventure Photo Packs Read More

4 Outdoor & Adventure Photo Packs

Photo packs have come a long way in the past decade, especially those that are targeted toward outdoor and adventure photographers. Alaska-based adventure photographer Dan Bailey takes a closer look...

Latest Learning Articles

5 Tips for Combating Red-Eye Read More

5 Tips for Combating Red-Eye

Red-eye doesn't have to ruin your photos. Learn 5 simple tricks to avoid and eliminate this undesirable photographic effect.


flash depth when using an umbrella

Dan Turcotte , Mar 10, 2011; 09:35 a.m.

I've tried to find this info here on photo.net but have come up short. I've recently taken a very shallow dip into off-camera lighting by getting a 580EX-II flash head for my Canon Xsi (450D) and an umbrella/stand setup. I suspect the answer for this is going to be, "it depends", but here goes: Is there a standard umbrella to flash distance or can the flash head just be placed anywhere inside the umbrella? I'm not sure if the flash should be really deep into the umbrella or if it should just sit at the edge.
A second related question is what zoom setting on the flash would be optimal? I've figured that the widest zoom (28mm) would make use of more refelective surface of the umbrella but, again, I didn't know if there are common standards.

As I said, I suspect that there is no one right answer for these questions but I'd be interested in hearing what others think/do.

Thank you.

Responses


    1   |   2     Next    Last

Ellis Vener , Mar 10, 2011; 09:43 a.m.

I'd geta 430 EX II instead of the 580 EX II, but to answer your question you'll get the best mix of efficiency and diffusion of light by settign the flash so it's beam pattern nearly fills the umbrella. You should flip dow nthe diffusion panel to make the beam wider or use something like a StoFen cap o nthe flash.

You get the best general lighting effect for portraits by having the edge of the umbrella about as far from the subject as the diameter of the umbrella bowl. Closer than that and the light will wr"wrap around' your subject more (less modeling effect), farther away than that and the contrast between lit and shadow areas will be become greater.

As to where to place the umbrella relative to the subject, that depends on what you think creates the best looking lighting for the subject and the effect you want to create. The closer the light is to the camera the flatter the lighting effect will be, the greater the angle to the subject fro mthe camera's point of view the longer the greater the modeling effect will be.

Matt Laur , Mar 10, 2011; 09:44 a.m.

Are you planning on using the umbrella for shoot-through, or as a reflector? As you've guessed, it really comes down to the look you're after, and the geometry (and size) of the umbrella. You don't want your flash far enough back or zoomed out to the point that it spills outside the umbrella.

Stop way down, and take a few shots of the lit umbrella so you can see the pattern you're getting on its surface, and then do the same with the pattern the umbrella gets you on a wall. That quick bit of feedback will teach you a lot about your particular rig.

Joseph Wisniewski , Mar 10, 2011; 11:51 a.m.

Is there a standard umbrella to flash distance or can the flash head just be placed anywhere inside the umbrella? I'm not sure if the flash should be really deep into the umbrella or if it should just sit at the edge.

Really deep. Every umbrella has a "focus point", which can be found either by lighting the umbrella with a constant light source and projecting it at a wall, or using some math. And Matt Lauer's suggestion to photograph some patters is great. You'll tell a lot looking at the pattern at about 1 umbrella width from the wall and 2 umbrella widths from the wall. Underexpose, don't let it blow white.
But you can get pretty close to the optimal placement with this quick and dirty trick.

  • put a yardstick across the lip of the umbrella
  • note the point where the stick crosses the shaft
  • back up a couple of inches. That's pretty close to the right point.

A second related question is what zoom setting on the flash would be optimal? I've figured that the widest zoom (28mm) would make use of more refelective surface of the umbrella but, again, I didn't know if there are common standards.

Ellis nailed it. Use your 14mm pop-up diffuser panel or a Stofen diffuser dome. The Stofen and a small pie plate with a cutout works even better.

Matt Lauer - You don't want your flash far enough back or zoomed out to the point that it spills outside the umbrella.

Unfortunately, speedlights tend to be set up for a rectangular pattern, so a setting that lights up the entire umbrella will have a lot of spill. Ellis's suggestion to use a Stofen helps a lot: despite being an oblong shape, the Stofen gives you a round pattern. Mount it in the center of a pie-pan, and things get even better.

Joseph Wisniewski , Mar 10, 2011; 11:56 a.m.

And just for grins, here's a graphic explanation of what happens when you have the light positioned near an umbrella's focus point.

Note how close the light is to the lip of the umbrella. That's why you use the 14mm diffuser or the Stofen omnibounce, because you've got a lot of angle to light up, about 140 degrees, almost a full hemisphere.


An umbrella in focus

Joseph Wisniewski , Mar 10, 2011; 12:03 p.m.

And here's what happens when you get too far back on the shaft. This is where you end up when you try to use a flash's default 50mm setting, or the 70-80 degree reflectors that come with a studio strobe. The overall effect is a "hot spot" in the center of the image, and ugly falloff.


Umbrella past focus. Don't do this!

Dan Turcotte , Mar 10, 2011; 02:20 p.m.

Thank you all for the very informative responses. I can see that I'll have a few excercises to do this weekend.

Incidentally, I have started reading "Light: Science and Magic", which I saw recommended in this forum and I have to say that it has been exceptionally imformative and illuminating (the pun somewhat intended). So thank you to whom ever suggested that book as well.

Thanks all.

Monika Epsefass , Mar 11, 2011; 02:33 a.m.

I'm just wondering about your answers, Ellis and Joseph. Why would you diffuse a light before it gets diffused by something else? That's the objective of having the umbrella in front of the flash to diffuse it, isn't it?
Correct me if I'm thinking too far out here. And if diffusing before diffusing is of advantage, would you need to adjust the flash exposure by +0.7 or +1 to compensate for light going stray?

Pete S. , Mar 11, 2011; 04:30 a.m.

When it comes to shoot through umbrellas set the zoom to 24mm on the flash and mount the umbrella as far away from the flash as possible. Shoot-throughs are IMHO more useful than white or silver umbrellas for using as a main light.

Ellis Vener , Mar 11, 2011; 12:44 p.m.

Why would you diffuse a light before it gets diffused by something else? That's the objective of having the umbrella in front of the flash to diffuse it, isn't it?

That is a good question. The purpose of the StoFen Omni-dome is to make the light from a small hot shoe mount flash mimic a bare tube flash wit h the light going out in a hemispheric shape as rather than a focused beam. this will fil the bowl of the umbrella better. The penalty is that you are diffusing the available energy over a larger angle.

If you are using TTL controlled or even auto controlled flash turning up the flash output compensation is not going to make the flash magically generate more light that its maximum capacity. The plus settings work when you are not already pushing the flash to it's maximum capacity ( a "full power dump") and are trying to make it brighter that the flash metering circuit thinks it should be.

As for why use a double diffusion technique in general: I do it because it can make a lovely light. I often use a soft box or umbrella diffused light behind a round 60" or 48" x 48' or 72" x 72' diffuser. this Works for both portrait work and still life work.


    1   |   2     Next    Last

Back to top

Notify me of Responses