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Photography Question 
Shawn Wilson
BetterPhoto Member Since: 4/25/2005
 

Flash power?


I am setting up a test photo shoot to learn more about group shots and need to purchase a couple strobes.

I've found a bunch out there, but I'm not sure about how much light I need.

I want to be able to get a group shot of 4 to 10 people from 10 ft away (camera is 10 ft back, lights can be anywhere).

I was looking at a couple 110w/s strobes, but would that be enough? Any more powerful than that and the price soars.

Also, for group shots like that, are softboxes better/worse than white umbrellas? Or would silver umbrellas be better?

Lastly, does one fire the strobes through a white umbrella typically for a large group shot, or reflect off it?

Thanks in advance!


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5/21/2005 9:51:45 PM

 
John A. Lind
BetterPhoto Member Since: 9/27/2001
  Shawn,
I recommend 500 Watt-Second strobes with continuously adjustable output. There are times I've wished for twice that power . . . although the price of 1000 W-S is prohibitive. 110 Watt-Second are pretty meager. Light modifiers eat light. How much depends on the specific softbox, umbrella, etc.

I've used smaller "shoot-through" umbrellas, and they work fine. However, on location with groups I prefer reflective, silvered ones. They're typically more efficient than white reflectives (eat less light) and retain a little more highlight (which you may or may not want.) The advantage with reflective is being higher than that light giving the reflected light greater elevation. Shoot-through end up lower than the light. In tight spaces with lower ceilings, a reflective umbrella can be brushing the ceiling . . . a shoot-through ends up much lower. Even if the ceilings aren't a limitation, shoot-throughs require a taller light stand and the back panel with controls ends up higher (can necessitate using a step-stool to adjust them) to get the same elevation of light source.

Softboxes control where the light goes much better, but on-location they are much more time consuming to set up and tear down (assembly and disassembly). OK if you have the time before and after. At weddings, one doesn't have that luxury unless one has a gaffer/grip to do it. They (mine at least) also eat more light than umbrellas do . . . especially if I add things like louvers. is spite of internal reflective panels to bounce light toward the front panel.

Primary reason for wanting higher powered lights in shooting groups is ability to back up the lights to about 12-15 feet or more from the grouping. The farther the light source, the greater the light spread . . . and the less the falloff of illumination from front row to back row. Get lights too close to a group with multiple rows, and the falloff from front to back can become noticeable. Light falls off in intensity at the inverse of the square of the distance . . . twice the distance from source is 1/4th the light . . . two stops less . . . three times the distance is 1/9th the light . . . just over three stops less.

-- John Lind


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5/22/2005 12:23:41 AM

 
Shawn Wilson
BetterPhoto Member Since: 4/25/2005
  wow... I can't even find very many 500 w/s stobes... at least not so far on ebay. With the price I've seen for even 220 w/s strobes, how many 1Ds cameras can I buy for the price of a single 500 w/s strobe??

While I understand the benefit of having a light capable of lighting a group of 30 in 4 or 5 rows... I'm not there yet. I'm looking to be able to light groups of 2 to 10 max and from 10 ft away.

110 w/s strobes might be small in the grand scheme of things... but are they worthless for my current needs?


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5/22/2005 1:05:40 AM

 
John A. Lind
BetterPhoto Member Since: 9/27/2001
  Shawn,
You need the light output; it gives ability to dial up or dial back as you require it for the light modifiers being used. I don't know what your budget is for lights, and how much you intend to use them. If this is for doing it professionally and you plan to use them continuously, don't scrimp on a good set of lights that are reliable, durable workhorses. It's one of the few things for which most of us don't have backup on-location (other than resorting to a relatively high power on-camera [on flash bracket] flash). I've seen this done by folks just starting out to save money too many times, the frustrations they've had with getting what they want in their photographs (regarding lighting) and ultimately spending what they could have at the beginning on better lights.

Check out the AlienBees B1600:
http://www.alienbees.com/

These got decent reviews from Bob Shell in Photo Techniques a few years ago. Inexpensive alternative to more expensive lights. The modeling light in these is a bit weak for on-location work; OK in studio where all the ambient light can be killed.

One of the workhorses I've seen used quite a bit are the PL1250 and PL1250DR from their PowerLight PL-2 series made by Photogenic:
http://www.photogenicpro.com/

Street price of a new PL1250 is in the vicinity of $500.

More expensive than the AlienBees but slightly less than the Photogenic lights are the 500 W-S Hensel Integra lights I use . . . is the "Photogenic" of Germany where they're made. Only a few major camera dealers in the U.S. import them and my decision to buy them included knowing there are limited sources for accessories and for service in the event they might need it.

Keep in mind that all the manufacturers give whatever guide number ratings the do using ideal setups with bowl reflectors, etc., that will maximize the guide number. In practical use, with various umbrellas and softbox configurations, a pair of them set back at about 12-15 feet lets me use f/5.6 with ISO 160 film. In high ambient light areas I might have to dial them back a little, but having the power in darker spaces is a lifesaver without having to move them closer and suffer greater front-to-back light falloff.

-- John Lind


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5/22/2005 8:00:31 AM

 
John A. Lind
BetterPhoto Member Since: 9/27/2001
  One additional thought . . . using monolights needs a flash meter. Get a decent one! The cheapies are frustrating to work with. One of the "best buys" on the used market is the Gossen Luna Pro F (F = flash meter). It's also an ambient meter that can read reflected and incident light in both modes. A basic analog meter, I've found it easier to work with than the modern digital wonders that require pushing buttons to wade through menus. Gossen, (a German company) has been one of the premier professional light meter companys for decades . . . siezing a good piece of the market from Weston (which was the premier selenium ambient meter maker for decades before Gossen).

-- John Lind


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5/22/2005 8:38:23 AM

 
Shawn Wilson
BetterPhoto Member Since: 4/25/2005
  Everything you're saying makes sense.

Looks like I'll have to do without for now though, spending $1000 on lights alone isn't in the budget.

Unless I find a good deal on one of the sites you gave me, I'll have to be a little creative.


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5/22/2005 1:29:47 PM

 
Shawn Wilson
BetterPhoto Member Since: 4/25/2005
  What about continuous lights... how would 500 watt daylight blue ones work?

I know they'll be hot... I'll deal with that later. I'm just trying to deal with the light level.

How does the light quantity compare between strobes and continuous? I know strobes are better in so many ways, but is a 500 w/s strobe the same as a 500 watt flood if the color temp is the same?


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5/22/2005 7:50:20 PM

 
Shawn Wilson
BetterPhoto Member Since: 4/25/2005
  Oh, and if it makes a difference I'll be using a Canon 50mm f/1.8 lens.

I keep seeing in strobe ads that they raise the light level so you can use say f/8-11. What would be wrong with ending up with a light level that needs f/3-4 ? Or even less since I've got a lens that will do it.

In the end, when you look at the pictures, would one see a big difference between a picture taken at f/8 1/250 and one taken at say f/3.5 1/60 ?


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5/22/2005 8:04:06 PM

 
John A. Lind
BetterPhoto Member Since: 9/27/2001
  Shawn,
Lens doesn't make difference. However, check your camera's X-Sync speed. I don't believe the Canon will flash sync above 1/125th (could be mistaken). The only ones I know of that will are a couple of Nikon's (FE2 comes to mind).

Hot lights . . . especially 500 Watt . . . even more so the blue (supposedly daylight type . . . more for plant growing) are called "hot lights" for very good reason. They get hot; mighty hot. The danger with them (aside from burning yourself and melting or scorching things that get too close to them) is your subjects starting to perspire under them! Light modifiers . . . softboxes in particular . . . are expensive as they must be made from materials that won't melt or catch fire.

I cruised ePrey looking at some 110 W-S lights. Their "GN" rating by the seller(s) is about 105 (ISO 100; feet), which is very weak. I use on-camera flashes with GN's of 140-160 (and have one rated at 200) for shooting wedding candids. These kinds of lights are more often used for studio background illumination (with a background reflector) or as a hair light (with a snoot) or as a "kicker" to get a little rim lighting around the side of someone's face and hair.

For shooting groups, I generally use f/5.6 at 1/60th . . . but watch depth of the group also working to keep it relatively flat and no more than two rows. The issue is depth of field at that aperture. It's why you don't want to shoot groups with the aperture opened up more than that. For a very deep group (three rows or more) I'll often stop down to f/8 and crank up the lighting. Reason for using 1/60th shutter speed is to pick up more ambient in the background that isn't influenced by the flash/strobes nearly as much as the subjects (for which you've set aperture and strobe power for proper exposure). Some altar areas in churches are deep, and some of those can have lots of dark wood. It keeps them from looking unnaturally too dark.

To summarize, f/8 @ 1/250th would have more depth of field to handle a larger group with more rows and 1/250th (if your camera will X-Sync that speed) would darken more distant background by significantly cutting down its ambient lighting. F/3.5 @ 1/60th risks depth of field problems with groups that have two or more rows and 1/60th will pick up more ambient in a distant background that won't get nearly as much light from your strobes as the closer subjects will.

In general, when using flash or strobes the exposure is set by lens aperture, not by shutter speed (other than more ambient light on a distant background which isn't influenced nearly as much by the flash/strobes).

-- John Lind


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5/23/2005 5:17:20 PM

 
Shawn Wilson
BetterPhoto Member Since: 4/25/2005
  Thank you. That's more what I was looking for. I'm the kind of person who needs to know the 'why' so I can know that I'm making an informed decision and not just doing what some guy told me to do. (even if that guy is very qualified)

The things that made the most sense are the DOF and background ambient light. Although I'm only shooting one row of people, I've still got a much better chance of making sure everyone is in focus if I can be closer to f/9 instead of f/2.

Although the background in my setup is lighter, it's still dark. I'm going to take a couple shots that way, and then the rest with a backdrop though, so I'll just have to do a lot of testing to see how well things will work.

Last thing, I've got a Digital Rebel(300D) and I'm upgrading to the new Rebel XT (350D) tomorrow. In the night shot mode the camera says it uses a longer shutter speed for the background to get a good overall exposure.

Can I achieve this same effect by doing a reading in camera with no flash of the scene, then using a flash but using the metered shutter speed... or somewhere in between where my light meter says it should be with a flash and where the camera says it should be without one?

Example - without a flash, camera says the scene (with no people, just background) needs a f/3.5 1/4. Flash meter with people and flashes says f/9 1/250. to get the background good and the people, would somewhere along f/9 1/60 sound right?

I know you can't know for sure, but does that basic scenario sound plausable?


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5/23/2005 5:50:12 PM

 
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