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FORUMS General Gear Talk Flash and Studio Lighting 
Thread started 27 May 2013 (Monday) 01:25
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How many 600ex-RT to equal Alien Bees?

 
fashionrider
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May 27, 2013 01:25 |  #1

Hey guys,

I've been using alien bees for my outdoor location shoots with an ND filter to lower sync speed to 1/200.

However, I'm tired of having to do that method and am interested in using canon's 600ex flashes. They have built in wireless triggering and HSS, which is what I want. I understand, HSS cuts the power of the flash a lot, so my question is:

How many 600ex's are needed to equal an Alien Bee B1600? Each flash is $500 so i'm assuming I'll need to spend thousands on multiple units. Just curious how many I'll need.


Gear List (5D3, 70-200 f2.8L IS II, Sigma 85mm f1.4, Sigma 35mm f1.4, 50 f1.8, 24-105L, Alien Bee lights, etc etc)

  
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apersson850
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May 27, 2013 03:57 |  #2

It's impossible to say, since the Joule designation of studio strobes shows how much energy can be put into the flash head. Then how much of that which actually reflects from the subject back to the camera depends on the reflector, angle, diffusers etc.

The guide number of a 600 EX-RT implies that the unit's own reflector is used, without any modifiers, and that the flash is mounted in the camera's hot shoe.

This can only be specified at a certain setup, and then you can just test it with a single flash unit replacing each studio strobe. Take a picture and see how it's exposed, comparatively. If you need to open up the aperture three stops, you can see that you need a guide number eight times as high.

Example:
Say you take a picture with strobes, and you get a good exposure at f/8. Your subject is 3.75 m from the light, so the light is equivalent to a guide number of 30.
Now you put one flash there, and find you need to open up to f/4 to get the right exposure. So the guide number of that flash must be 15. Since combined guide numbers are computed as the square root of the sum of the squares of the guide numbers of the individual flashes, you need four such flashes to come back to f/8 for the exposure.
sqrt(4*15^2)=30


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umphotography
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May 27, 2013 07:22 as a reply to  @ apersson850's post |  #3

a couple of 1600's and a couple of vagabond minis are a much cheaper and efficient way to go v/s the 6-8 600's you will need to get the same light. You can keep using the ND's to reduce your DOF as well for individual portraits

Its a bulletproof system. Its what what i use outside.


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Flores
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May 27, 2013 07:47 |  #4

if you trigger them using the right pocket wizard setup, you won't have to limit yourself to 1/200...




  
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umphotography
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May 27, 2013 07:52 |  #5

Flores wrote in post #15971556 (external link)
if you trigger them using the right pocket wizard setup, you won't have to limit yourself to 1/200...

That depends on the camera. With 1600's i could get my MKIV @ 1/2000.. my 5D3,, cant get it past 1/200.


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elv
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May 27, 2013 08:38 as a reply to  @ umphotography's post |  #6

You might want to look at the Cheetah Flash as that has FP HSS and 150Ws or 300Ws -

http://flashhavoc.com …cl180-godox-ad180-review/ (external link)


To answer the question though regarding how many speedlites to equal an Alienbee, using a modifier like an umbrella etc your looking at 4 speedlites to match an AB800.

Thats without HSS, with HSS on you loose another 1 to 1.5 stops, so that's at least 8 speedlites in HSS to match the one AB800 and an ND filter.

So one Cheetah Light 360 would make more sense with HSS.
.


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dmward
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May 27, 2013 08:49 |  #7

Keep in mind that when the shutter exceeds X-sync the flash duration has to be long enough to illuminate the subject throughout the shutter slit's travel across the sensor. Speedlites do it with a rapid pulsing, becoming a constant light source. With monolights, first the camera has to be spoofed into sending a fire signal beyond the x sync speed, i.e. FP-sync used for High Speed Sync with speedlites. Then, as Pocket Wizard does with ControlTL, the timing of FP-sync from camera to light can be optimized. Or just passed through as Yongnou and others do.

This approach uses the tail of the monolights light burst to illuminate the subject. Again, a constant light source. Since the flash output is diminishing there is a gradated dimming as the shutter slit crosses the sensor.

In either case, since the light required to illuminate the subject has to available for a longer period of time, the energy in the capacitor(s) has to be used over a longer duration which means less peak output.

What all this means is that we have three technical approaches that can be used, depending on the specific requirements.

My inclination is to use ND filters when the lights have to be a significant distance from the subject. Use HSS with 600EXs when the light can be close to the subject as a fill. Use CheetahLight CL-180 in H mode when the light is close to the subject in a modifier as main.


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May 27, 2013 11:57 |  #8

Buff web site states f16 +9/10 for AB1600 with 7" field reflector at 10'. That reflector has an 80 degree spread angle.

24mm lens on FF camera sees 84 degrees diagonal, so if we look up Canon's guide numbers for 24mm lens, it is about GN92 or f/9 at 10'...but we also know from many tests metered with flashmeter that the guide number claims are overrated by about +1EV, so f/6.3 might be a better real statement of expectation for the speedlight...so about -3.5EV less light than the AB1600.

So you would likely need about 12-14 speedlights to provide equivalent light!...6-7 speedlights if you swallow the Canon juice about power claims.


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fashionrider
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May 27, 2013 13:34 |  #9

okay thanks everyone for the input. If I need 4+ speedlights to match a b800, that's definitely not an option anymore. Haha! damnit! oh wells.


Gear List (5D3, 70-200 f2.8L IS II, Sigma 85mm f1.4, Sigma 35mm f1.4, 50 f1.8, 24-105L, Alien Bee lights, etc etc)

  
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fashionrider
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May 27, 2013 13:38 |  #10

umphotography wrote in post #15971511 (external link)
a couple of 1600's and a couple of vagabond minis are a much cheaper and efficient way to go v/s the 6-8 600's you will need to get the same light. You can keep using the ND's to reduce your DOF as well for individual portraits

Its a bulletproof system. Its what what i use outside.

I've been using it so far too and I've managed well. I use a vari-ND filter, so it's sort of a pain to put it on since I have to take the lens hood off. I also have difficulty shooting in brightly lit areas at f1.4, and underexposing the BG 1-2 stops for effect. that forces me to really crank the darkness, and it's hard to focus in a dark viewfinder.


Gear List (5D3, 70-200 f2.8L IS II, Sigma 85mm f1.4, Sigma 35mm f1.4, 50 f1.8, 24-105L, Alien Bee lights, etc etc)

  
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umphotography
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May 27, 2013 15:47 |  #11

fashionrider wrote in post #15972510 (external link)
I've been using it so far too and I've managed well. I use a vari-ND filter, so it's sort of a pain to put it on since I have to take the lens hood off. I also have difficulty shooting in brightly lit areas at f1.4, and underexposing the BG 1-2 stops for effect. that forces me to really crank the darkness, and it's hard to focus in a dark viewfinder.

lower your iSO to 50 on the 5D3. I try to go no more than a 2x when shallow,, look for darker contrasty backgrounds v/s lighter backdrops


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fashionrider
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May 27, 2013 16:09 |  #12

umphotography wrote in post #15972922 (external link)
lower your iSO to 50 on the 5D3. I try to go no more than a 2x when shallow,, look for darker contrasty backgrounds v/s lighter backdrops

yeah, i drop it to iso 50 whenever I use ND filters. Usually I look for very shaded areas, but sometimes, it's just impossible and you're faced with the most difficult situations known to man. haha.


Gear List (5D3, 70-200 f2.8L IS II, Sigma 85mm f1.4, Sigma 35mm f1.4, 50 f1.8, 24-105L, Alien Bee lights, etc etc)

  
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Casual
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May 27, 2013 16:09 |  #13

umphotography wrote in post #15971564 (external link)
That depends on the camera. With 1600's i could get my MKIV @ 1/2000.. my 5D3,, cant get it past 1/200.

Have you updated your PW's firmware? They have 5d3 updates which can get you up to 1/8000 I believe.


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May 27, 2013 17:50 |  #14

Casual wrote in post #15972980 (external link)
Have you updated your PW's firmware? They have 5d3 updates which can get you up to 1/8000 I believe.

First, the ControlTL firmware supports Hyper Sync which works better with larger Buff lights at lower power settings to elongate the tail.
Second, HyperSync, like HSS on speedlites significantly reduces the power available to illuminate the subject.
Third, with HyperSync, the higher shutter speeds may increase the gradation of light since its a much narrower slit traveling at the same speed. Which means less light stricking the sensor at any point in time.


David | Sharing my Insights, Knowledge & Experience (external link) | dmwfotos website (external link)

  
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bobbyz
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May 27, 2013 19:58 |  #15

Can we see some sample shots? I mostly use f2.8 and that is not any issue when using 3 stop fixed B+W in back lit situations. If I need more I add CPL. Vari ND look good on paper.

Maybe you get those lee kid of filter which you can add after focussing but then shootinga t f1.4, small movement and OOF.


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How many 600ex-RT to equal Alien Bees?
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