Watt per Second comparison- strobe vs flash

Nikon AF-S DX Zoom-Nikkor 18-70mm f/3.5-4.5G IF-ED

03/11/2009 12:45:16 PM · #1

I'm looking at getting some proper studio strobes, and see they all have w/s ratings.

In the past I've used my two off-camera flashes, Sigma DG 500 Supers, and wonder if anybody has a guess as to what their full power w/s rating might be. I looked through the manual, but it either sucks, or I'm blind.

Any help?

Also:

Say I want to be able to throw a good light from a strobe, through a softbox, onto a subject about 10 to 15 feet away. What w/s rating would I need?

THANKS 4 ANY HELP! :-)

johst582

Nikon D80

03/11/2009 01:03:42 PM · #2

Sorry for nitpicking, but the rating of studio lights is in watts times seconds = joules = the total energy of a flash (without saying anything about its duration).

I did a quick google, but couldn't find info for your flash. However, a Nikon SB800 was mentioned to emit 60 Ws, so perhaps this Sigma flash is in the same neighbourhood.

03/11/2009 01:06:08 PM · #3

I've also noticed that the AlienBees B800 are advertised as 800Ws but in the specs it says "320 True Ws" and "800 Effective Ws".

Does that mean that if I buy, for example, an Opus brand strobe advertised as 250Ws, that Opus is advertising it Effective, or True number?

03/11/2009 01:07:07 PM · #4

Originally posted by johst582:

Gadzooks, I'm so confused! :-O

03/11/2009 01:17:28 PM · #5

Thanks for the link!

So, going by "Guide Numbers":

Guide number for my Sigma flashes is "50" at ISO 100 and 105mm head position.

From the link:

SB-600 @ 1/1 @ 24mm zoom = 85
SB-900 @ 1/1 @ 24mm zoom = 88
SB-800 @ 1/1 @ 24mm zoom = 98
SB-600 @ 1/1 @ 35mm zoom = 98.4
SB-900 @ 1/1 @ 35mm zoom = 111.5
SB-800 @ 1/1 @ 35mm zoom = 125
AB400 @ full w/standard reflector = 118
AB400 @ full w/11" long-throw reflector = 220
AB800 @ full w/standard reflector = 172
AB800 @ full w/11" long-throw reflector = 320
AB1600 @ full w/standard reflector = 236
AB1600 @ full w/11" long-throw reflector = 450

=============

So an AB400 can throw roughly twice the light, it seems?

03/11/2009 01:26:57 PM · #6

Originally posted by Strikeslip:

So an AB400 can throw roughly twice the light, it seems?

Twice the guide number = 4x the light output, if I am not mistaken...

R.

Prof_Fate

03/11/2009 01:35:24 PM · #7

Speedlight type flashes are at most 50-60ws and most any modifier cuts that down. They are measured at a very specific distance, zoom amount (most of them will do a zoom in their head), lens, etc.

Studio lights are harder to measure in GN terms as most come with no modifier, and you can get almost any modifier - which of course modifies the look of the light as well as it's output. A softbox can cut the light by a stop or more for example ( in other words, by 1/2).

Go read //www.paulcbuff.com/forums/viewtopic.php?f=10&t=50 to learn about wattseconds - true vs effective.

03/11/2009 03:16:45 PM · #8

Thanks for the replies, I'll take a look at the link.

I just got back from spending a bunch of money. At least it's sort of like found money, though, as I made it doing some product photography last week. So now I'm more well prepared to do better quality shots at a gig in a week & a half, which is for a high-profile business and will hopefully lead to some good word-of-mouth for me. Some of my shots might go on billboards & buses, which would be a kick to see.

I got this Elinchrome Studio Lighting set.

And also got this Elinchrome Skyport wireless trigger.

Unfortunately I'm busy all day and night taday and Thursday, so I won't be able to play with it until Friday night. :-( Gagh, it's like Christmas delayed!

03/11/2009 03:18:38 PM · #9

Originally posted by Bear_Music:

Originally posted by Strikeslip:
So an AB400 can throw roughly twice the light, it seems?

Twice the guide number = 4x the light output, if I am not mistaken...

R.

I asked the guy at Vistek and he said these are 4 or 5 times the output, so hopefully you're both right. :-)

03/11/2009 03:29:13 PM · #10

Originally posted by Prof_Fate:

I see. I've been shooting through, and bouncing off, umbrellas with my flashes, so I don't expect any surprises vis a vis not as much extra light as I expected. It will be nice to be able to gain some space between subject and diffuser. Modeling lights will be nice, too. :-)

03/11/2009 03:47:50 PM · #11

Originally posted by Strikeslip:

You betcha. You'll wonder how you ever lived without 'em...

R.

BTW, go here and see my post from yesterday, whcih mentions your uncle in passing :-)

k4ffy

03/11/2009 04:23:32 PM · #12

sorry for the ignorant question, but what's the difference between a "strobe" and a "flash"?

03/11/2009 04:31:00 PM · #13

Originally posted by k4ffy:

sorry for the ignorant question, but what's the difference between a "strobe" and a "flash"?

I figure a flash is something you can mount into the hot-shoe on your camera, while a strobe is a bigger beast which plugs into a wall outlet or battery pack and is fired via sync chord or wireless trigger. That's my guess, but it may be wrong. :-)

ETA, the strobes I bought have Modeling Lights, which are always on, but at a low enough brightness as to not make someone squint. And the modeling lights change their intensity depending on how brightly you have the flash set to fire. That way you have a real-time view of how the light will fall and balance between multiple strobes. I've read a blurb about a modeling light in a flash, but don't know if it's the same thing.

Message edited by author 2009-03-11 16:35:06.

Canon EF 24-105mm f/4.0L IS

03/11/2009 04:37:57 PM · #14

Originally posted by Strikeslip:

Originally posted by k4ffy:
sorry for the ignorant question, but what's the difference between a "strobe" and a "flash"?

I figure a flash is something you can mount into the hot-shoe on your camera, while a strobe is a bigger beast which plugs into a wall outlet or battery pack and is fired via sync chord or wireless trigger. That's my guess, but it may be wrong. :-)

That's pretty much what it's like, nowadays. Some would reserve "flash" for the built-in strobes some cameras have, and that makes more sense to me. So a 580EX, for example, is a strobe as well to me.

Back in the paleolithic when I started, "flash" meant bulbs and "strobe" was an "electronic flash". If you want a real hoot, google up on the topic of 22B Flashbulbs; these were bulbs the size of regular lightbulbs that just BLASTED out light when they popped. They are what we used for architectural interiors; we had a home-made wooden synch box that we plugged regular floodlight heads/reflectors into. We'd use floods for "modeling" lights, then replace all the bulbs with 22B's for each exposure. There was, at the time, no such thing as an easily portable strobe setup powerful enough to light large interiors, but these 22B bulbs were stunningly powerful.

R.

Prof_Fate

03/11/2009 04:53:24 PM · #15

Let me confuse things...
A modeling light in a speedlight (nikons term, but it identifies the battery power hot shoue mounted type flashes well IMO) is a low power stroboscopic light emmission. (confused?) Basically the regular flash tube goes off very rapidly at low power so that you can see where the shadows will fall. HSS (high speed sync) mode works in the same way.

To me (age 47 if that bears on this discussion) flash is on-camera as I was raised in the era of flash bulbs and watched movies with depictions of flash powder for added light. I'm used to hearing the term 'studio strobe' rather than 'studio flash', so to me strobe is what you use in the studio, be it a monolight or pack and head system.

strobes take modifiers and flashes don't (the strobist idea is changing that bit though - but then 'srobist' is geared to working with 'flash'. Confused yet?)

Modeling lights on strobes serve many purposes. As slippy said, you can use them for a relative idea of pwer setting on the strobe. You can also use them to see where the shadows will fall. In a dark studio they provide the light to walk around and see with, and can be very handy to aid the camera in getting focus. And with today's higher ISO capable cameras you can use them as hot lights for 'natural' light portraits.

The latest trend has been to take CF (compact flourescent) bulbs of daylight WB and good quality (read expensive - like $25+ per bulb) and put them in softboxes (from strobes) and use them like hot (aka continous) ligbts, the westscott spiderlight being the biggest name of these.

robs

Canon EOS R6 Mk II

03/11/2009 06:20:16 PM · #16

Originally posted by Bear_Music:

these were bulbs the size of regular lightbulbs that just BLASTED out light when they popped.

I remember as a kid using the little bulbs in my fathers 35mm flash... It was a cool thing that you un-twirled and it formed a circle by spinning it around and put in a single glass bulb....not sure how to explain that in words but was cool. About the only think I figured out is the damn things go HOT!! I cannot imagine those things in light bulb size :-0/

03/11/2009 06:38:23 PM · #17

Originally posted by Prof_Fate:

YES! That's the term I was looking for! Speedlights mount on cameras, strobes are standalone! Thanks!

R.