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Photography Question 
Barb  Rathbun

Studio Lighting

I have a Canon 5D and will be doing a studio shot with it using Alien Bee lights. Do I need to set the shutter at the maximum sync speed? If so, does anyone know what that is for a 5D? Could I shoot at less than that? The reason I'm asking is that when I use 1/250 of a sec., I have to open my aperture to 4.5 to get light that looks good. I'd like to shut the aperture down to about 8 to get maximum sharpness (and slow down the shuuter speed to correspond), but for some reason, I can't get the lighting to look as good. Does anyone have any suggestions?

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5/4/2009 7:37:17 AM

Alan N. Marcus   I envision that you are talking about strobe (electronic flash) equipment. If true, your shutter speed considerations revolve around what we call synchronization.
Allow me to explain:
Since the duration of the electronic flash is so extremely short, the main problem is to make sure the flash fires at the moment when the camera shutter reaches maximum opening. To achieve your camera has a built-in timing circuit. You are advised to read the camera manual and bone up on this subject because this dictates the range you can use as to shutter speed. If this range is violated, the flash will fail to record in part or in total. Donít worry, the shutter speeds you referenced are within the permissible range. Do however read about synchronization, you will be glad you did.
You need to know that the flash duration of your strobe is exceedingly short. It averages better than 1/1000 second. It is so extremely short that varying the cameraís shutter speed has utterly no impact on exposure. However if strong light is present (ambient light) we must use a fast shutter speed. This avoids ghost images and reduces interference whereby the ambient light unduly impacts on the exposure.
As to lens sharpness Ė Generally a camera lens will perform at it sharpest about two f/stops stopped down from maximum. This will likely be around f/8. It is unlikely that you will be able to detect differences in sharpness wider opening like f/5.6 or even f/4.5, unless the presentation will be giant prints. Maybe you think you need f/8 because you desire a lengthened span of depth-of-field. Thatís OK however the classic view of a portrait is shallow depth-of-field. This causes the background and foreground to be out-of-focus, generally achieved by setting the aperture around f/5.6.
So whatís wrong? Why is the view screen image dark and noisy? The high quality studio strobe is built with two light sources. A flash tube to provide the brilliant flash for the picture taking instant. A built-in standard tungsten lamps called modeling light to allow you to pre-visualize the lighting as it will be furnished by the flash. Usually the modeling light is sufficient to allow you to compose and focus. These modeling lights either quench for the exposure or they are too feeble to affect the flash exposure.
No modeling lights? You need to provide sufficient ambient light to allow composing and focusing. Keep in mind, exposure is based on the flash that will fire not on ambient light.
Best of luck,
Alan Marcus

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5/4/2009 9:34:04 AM

Jon Close
BetterPhoto Member Since: 5/18/2000
  5D manual, p. 102.
Fastest sync speed with hotshoe speedlights is 1/200. Studio strobes like your Alien Bees actually take fractionally longer to reach full output and the manual recommends 1/125 or slower with them.

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5/5/2009 5:24:14 AM

Barb  Rathbun   Alan--thanks so much for the detailed answer to my question. My camera manual recommends no faster than 125 for non dedicated lights. I knew that shutter speed with studio lights had no impact on exposure but I never understood why before. Evidently, the exposure is determined only during the 1/1000 of a second that the lights are firing. I've also heard of sync speed before but now I understand that it's the time of maximum opening of the shutter so if it's not synced correctly with the flash, the flash might go off as the shutter is partly closed resulting in a black line down the side or bottom of the picture. I believe I understand this now thanks to your detailed answer.


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5/5/2009 7:24:43 AM

Barb  Rathbun   Thanks, Jon. It looks like 1/125 or slower is the correct sync speed.


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5/5/2009 7:26:44 AM

Kevin W. Hammond   Barb, you are describing the normal relationship between shutter speed and aperture when shooting under ambient (avaialble) lighting conditions.

Because strobes fire so fast, only the aperture has a bearing on the flash portion of the exposure.

When shooting with a strobe,

1. Aperture determines how much light from the strobe gets into your exposure

2. Shutter speed determines how much ambient light gets into your exposure

3. ISO impacts both light from the strobe and the ambient, but should typically be low enough that it effectively shuts out the ambient.

The sync speed for a 5D is 1/200. At 1/250 you have good chance of seeing the shutter in your image ... a big vertical black bar, likely at the right side of the image. In general, do not shoot faster than 1/200 on a 5D unless you are specifically using high-speed sync and the E-TTL capabilities of Canon strobes (i.e., a 580EX II or similar.)

Assuming you want the exposure to be 100% driven by the strobe at f/8, set your aperture at f/8, your shutter speed to 1/200 and your ISO to 400 or lower. (Note, as you lower ISO you'll have to increase flash power.)

Then meter your strobe using either a flash meter (like a Sekonic L-358) or by taking a test frame. Adjust the power of the strobe up or down to reach f/8 at your selected ISO.

At 1/200, little - if any - ambient light should get into your image. To prove this to yourself, turn off the strobe and take an exposure at f/8, 1/200 and your selected ISO. You should see an almost black image under any typical office lighting conditions.

As you slow down the shutter, more and more ambient light will enter your exposure. You can use this creative control to start using the ambient for fill, balance against the strobe, etc.

However, for a typical studio shot lit entirely by strobes, you'll be at 1/200 on a 5D and not worrying about the ambient at all.

According to the Alien Bees manual, full power flash duration of an AB400 is 1/6400, an AB800 is 1/3200 and an AB1600 is 1/1600. Therefore, you should be fine at 1/200 and not need to go slower, unless as I outlined above, you specifically want to bring ambient light into your exposure.

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5/5/2009 7:47:52 AM

Roy Blinston
BetterPhoto Member Since: 1/4/2005
  I have the Canon 20D and 50D and my (max) sync speed is 250sec. I would assume the 5D is the same (?).

I use 2 x 500w strobes, plus a backlight, and shoot at 250sec f8, 100 ISO. Camera distance to subject is around 12 feet. Lights to subject is around 10 feet.

If your pics are coming out "dark" maybe your strobes are only 240w or 125w. If so, you may have to up your ISO and do some test shots.

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5/5/2009 9:13:54 AM

Kevin W. Hammond   The 5D is the odd one in the bunch, supporting a max sync speed of only 1/200 as opposed to 1/250.

It caused me untold grief for the first week as I assumed it was 1/250 just like my 20D's and I was perplexed by the seemingly random black bars.

Once I read the fine manual and discovered it was 1/200, my problems went away.

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5/5/2009 9:18:04 AM

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