Why Strobes Over Continuous Light

Discussion in 'Lighting Equipment' started by dragonflydm, Jun 2, 2006.

  1. Why Strobes Over Continuous Light
    By Joshua Hudson, www.dragonflydigitalmedia.com

    You are on a budget and you want to make your own studio lights. Shop online
    and you will find that lighting is not cheap, but where do you start. Are the
    Watts on a light bulb the same as the Watt Seconds on a Studio Strobe? Here is
    a little primer on what the average "photo Joe" needs to know about light.

    First off, watts are not a measure of light. Electrical power is measured in
    watts. A household light bulb is measure not by the amount of light produced
    but by the very economics driven "electrical power used." So we can never
    really measure light by power consumption. This is why you find that a
    fluorescent bulb, which is much more efficient, can create more light at 46
    watts than a 500 watt halogen or incandescent light. And because it is more
    efficient in its use of wattage, it produces much less heat.

    The only true measures of light are Guide Numbers, Lumens and LUX.

    A LUMEN is a unit of measurement of light. It measures light much the same way
    we do a foot/candle (or Lux). Remember, a foot-candle is how bright the light
    is one foot away from the source. A lumen is a way of measuring how much light
    gets to what you want to light! A LUMEN is equal to one foot-candle falling on
    one square foot of area.

    Candlepower is a rating of light output at the source, using English
    measurements. Foot-candles are a measurement of light at an illuminated object.
    Lumens are a metric equivalent to foot-candles in that they are measured at an
    object you want to illuminate

    You can find the lumens of any continuous bulb usually on the packaging. It
    takes a lot of lumens to light up a set. Human eyes are much more sensitive to
    light than cameras and what seems incredibly bright to use is barely
    significant to most of our photos. Bare minimum portrait lights should start at
    10,000 lumens. I would not even try to do a portrait sitting without my main
    light being at least 20,000 lumens. With unscientific research, I estimated my
    test with continuous lighting to make a 20,000-lumen light about a 150 watt-
    second strobe.

    So watt seconds can't possibly be a unit of light measurement either, huh? Yup!
    Exactamundo! Watt Seconds (ws) are a unit of energy, commonly used in
    advertising for AC-powered studio flash units. It is not, however, a unit of
    actual light output, so comparing the watt-second ratings of different flash
    units is not usually useful. This is why you get people like Paul Huff giving
    actual watt-seconds vs true watt seconds. True watt seconds is a watt second by
    definition, while actual watt seconds are white lightning�s way of saying their
    flashes are brighter because they use more efficient capacitors. I totally
    believe that Paul is telling the truth that his lights are brighter than other
    strobes rated at the same ws but there is no such thing as an actual watt
    second. Nor can you measure lumens by watts seconds.

    What you CAN do with strobes is measure the light with a Guide Number (GN). The
    GN is used in flash calculations to determine the appropriate aperture required
    to cover a certain distance or vice-versa. To find the aperture (f stop number)
    required to take a photo of a subject you divide the flash unit�s guide number
    by the distance to the subject. To find the maximum distance that can be
    reasonably illuminated using the current aperture setting you divide the guide
    number by the f stop number. In each case it�s the distance from the flash to
    the subject that�s important, not the distance from the camera to the subject.
    These two distances may be the same with on-camera flash, but not with off-
    camera flash or when using bounce flash.

    f-stop number = GN / distance
    distance = GN / f-stop number

    Note that you are not getting a reading in lumens, but a way of figuring
    exposure. So then how are you going to determine if your continuous light is
    going to be equal to your flash? Simple. Look at your exposure on your camera
    and compare. You will find that a 1000 watt halogen will put out just under
    10,000 lumens and gets you about 1/60th, f/2.8 on ISO 200 at 5 feet away.. That
    is a really slow shutter speed and very wide f/stop for a studio light. Even
    the cheapest $30 Vivitar 283 is going to give you a GN of 85-- which means at 5
    feet you are going to get an f/stop of f/16 at the shutter sync speed of your
    camera on ISO 200. That is an average of five stops difference.

    But don't let that discourage you from making a good set of home bees or
    continuous lighting. There are some great reasons to have continuous light. You
    get a great idea of what your photos will look like, unlike strobes. Continuous
    lighting is great for products as well, since they do not move and you can
    adjust your f/stop for slower shutter speeds. And if you are a fan of very
    small apertures, you can get some great shallow depth of field shots.

    Most of all, you can still shoot continuous because it is fun. Home Bees are
    simple to make, cheap and a really fun time for a photographer on a rainy day!

  2. What you don't mention is that in order to achieve say F8, with hard lights. You can burn down your house.
  3. There is nothing morally wrong with continuous lights; its just that continuous lights are:

    1. Hot, as Steve noted. They make portrait subjects sweat.

    2. Hard on a portrait subjects' eyes, making people squint after a little while.
  4. " There are some great reasons to have continuous light. You get a great idea of what your photos will look like, unlike strobes."

    Once again the myth of only hot lights providing WYSIWYG lighting rears it's hot, sweaty head.

    If you try to use portable camera flashes that don't have modeling lights or cheap studio strobes with dim 100 watt model lamps this blanket statement is correct. But those are almost as poor a choice for studio lighting as hot lights.

    If you use studio strobes with 250 watt or higher modeling lights you can see exactly what your lighting will look like and you can avoid all of the disadvantages of using hot lights.

    Garry Edwards has written a definitive article on different lighting equipment which is archived in the Administration section of this Lighting Forum. You might want to check it out.
  5. nz


    I think I'd rather use flash powder. This new fangled continous light won't last.
  6. Brooks, Before I had come across this forum, I had bought into the Hot-Lights-Are-Good-For-Beginners idea. I quickly realized that they are a nightmare to use for portraits of kids, and that they simply cannot provide adequate power for large format portraits of children. Interestingly, by my calculations, hot lights aren't really much cheaper than strobes. Sure, the light itself is cheaper, but the light modifiers (e.g., softboxes) tend to be costlier. Lastly, ultraviolet light injury to the eyes is a bigger concern with hotlights than with strobes, because of the longer duration of exposure to the damaging rays.
  7. I just wanted to offer an alternate perspective. In certain LIMITED (don't flame me) situations I prefer continuous lights. When I'm photographing a headshot in studio I often prefer kino-flos (they are high frequency flourescents that run cool) over my profoto 7a 1200 pack with 7 foot octa. I am able to shoot F4 @ 125 which I like for the limited d.o.f. Often my profoto pack at the lowest power setting cannot keep pace with my shooting style. When a person has a true genuine laugh or smile it changes rapidly. It is not unusual for me to shoot 3 or 4 fps over the course of a laugh (I don't do this for the entire shoot - just when capturing a truly alive and real moment). My pack can't keep up with that pace. On the downside kinos are really heavy compared to flash heads and require heavy shotbags on heavy stands, they offer only one kind of diffused light which is very limiting at a ridiculously low level compared to strobes. Also, if your subject moves too much they'll be out of focus. The upside is they are continuous which does make seeing the shot easier for me, run cool, give off a very flattering soft light for portraits, I prefer the look of the kino catch lights in the eyes over the big saucers of a softbox, some subjects find strobes disconcerting and become tense compared to continuous, and I get to use them on video and film shoots because they're continuous. Lastly, I've read about really successful commercial photographers that use them for table top photos because they find it easier to see the shot using continuous lights.
  8. John,

    I know...I know. What else can I say?
  9. "I think I'd rather use flash powder. This new fangled continous light won't last."

    Flipping channels the other day, I ran across a scene where they were shooting with flash powder. Poof! Big puff of smoke! Only...it was broad daylight, sunny even.
  10. nz


    Plenty of fine photos have been made with flash powder. Why change?
  11. Before strobes, most folks used continuous light, ie lights on stands. They were also smarter, and whined less. Electricity cost radically more too. A typical pre WW2 settup used a serial-parallel switch, so lamps could be settup with less heat, then flipped to the brighter position for shooting. Some studios had variacs, so the light level could be dropped real low the settup, and at full during shooting. Today folks have to poo poo continuous light, because they are less educated, because magizines and web sites concern of the liability of taking responsiblity for dumb folks making wiring errors of a series parallel switch bank, or fathom using a variac. In past eras alot of studios made their own gear. Today the "buying solution" is the only answer. Strobes are also radically lower in cost too.
  12. Long ago a typical home shooter just used the special 3 way photobulbs for continuous light with Smith Victor reflectors. These Mogul and sometimes edison base 3 way bulbs just went into regular 3 way sockets. They often had just 15 watts at the lower setting, and 150, 200 or 250 watts at the high setting. Here one just didn the modeling with the setting, there was no special series-parallel boxes or heavy expensive giant variacs to mess with. One just modeled with 15 watts, then switched to the high setting for a shoot. Since many of these special bulbs are now long gone, I ssumme folks today assume folks long ago fried their models, and left these "hot wattage" lamps on all the time.
  13. Kelly,

    I can remember shooting corporate head shots with tungsten lightgs in the seventies.

    I was no smarter then than I am now and I know for a fact that I whined at least as much then as I do now. Hot lights've got nothing to do with my appreciation of a fine whine ! #8^)
  14. There is a revival of the use of HMI lights for big-budget fashion and product photography. There is misconception of people thinking that all continous lights are cheap and hot. I wish I could afford just one HMI light.

    I love to shoot with the modeling light of strobes.

    Hard lights are good not only for product but people too.
  15. Hey...I just wanted to give some perspective on how lighting works...not judgement on which is better flash or strobes.

    Did some people even read the article?
  16. Joshua,
    "Hey...I just wanted to give some perspective on how lighting works...not judgement on which is better flash or strobes. Did some people even read the article?"
    Well, I read every word, and I'm sure others did too.
    I appreciate the effort you went to but you did more than offer a primer on how lighting works, you expressed opnions about what you perceive to be the benefits of tungsten lights.
    Now, not many experienced photographers will agree with your views so please don't be surprised if other people express different opinions to your own.
    We welcome diversity of opinion on this forum, we don't delete posts just because we happen to disagree with them, nor do we expect other readers to agree or disagree silently.
  17. Joshua, I appreciated your article. What you may not be aware of is that some of members of this forum are pretty sensitive about the subject of hot lights. This certainly has nothing to do with the hot lights themselves, but with the bad behavior of some of their adherents. This thread contains an example.
  18. I will never use "hot lights" again after having a photo flood bulb literally explode ...THANK GOD it was not turned towards any living thing at that time!!!
  19. Clark; over time I have seen flashbulbs, tungstens and zenon strobe tubes shatter. I have seen folks get shocked by strobes and by unplugging a bank of fluorescent bulbs; the ballasts give a kickback voltage the grip had his finger touching one plug prong. I have seen tungstens break by a kid squirting one with a squirt gun, or fluorescents break by a stray hockey puck. Before about 1948 if one got cut by a broken Fluorescent tube one got this cut that would never seem to heal. Calling tungtens hot lights shows one is a newbie; it was not the term used long ago. What is funny is up the thread is that Brookes mentions using 250 watt bulbs for modeling lamps; but my copy stand uses four 250 watt bulbs!
  20. Hey...I just wanted to give some perspective on how lighting works...not judgement on which is better flash or strobes.​
    You picked a strange choice of thread title then.
  21. "When a person has a true genuine laugh or smile it changes rapidly. It is not unusual for me to shoot 3 or 4 fps over the course of a laugh (I don't do this for the entire shoot - just when capturing a truly alive and real moment). My pack can't keep up with that pace."
    good point
    I am used to shooting weddings and indeed shoot at 2-3 photos a second to get one eyes shut, one dodgy face and one perfect and natural real emotion.
    Has anyone tried the new led light panels that are like kino-flo but tougher and lighter. they come with aa battery packs for location video shoots...?
    Wjat do people think of daylight bulb continuous lighting using bigger versions of the new energy saving bulbs?
    Nice article here:

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