Flash power

This short article is about an important parameter of external flashes - power.

Is flash power important?

Is flash power important?

Nowadays, camera manufacturers are trying to sell the buyer the number of megapixels, lens manufacturers - a huge zoom ratio, and flash manufacturers - the leading number of flash. In all three situations, neither the megapixels, nor the zoom, nor the guide number can be the only, let alone the main, criterion when choosing photographic equipment.The flash guide number is a numeric value in meters that indicates how far the flash can illuminate the area. Flash guide number and flash output are synonymous. Typically, flash output is measured at ISO 100 or ISO 200 and the wide-angle flash zoom position with the flash head pointed straight ahead. This assumes that the lens aperture is F / 1.0 (and where are such lenses?) For example, in the instructions for the flash SB-700 declared:

Flash power. Taken from instructions

Flash power. Taken from instructions

But here I have not met a strict standard for measuring the leading number. Also, measurements are complicated by the fact that different flashes have different zoom, and when the flash zoom changes, its range changes. Actually, with a different zoom value, the flash can show a different value of its guide number. Also, measurements should be carried out at a certain temperature. Another important factor is the shooting mode when measuring the leading number. For example, in TTL mode and in M ​​mode with power 1/1, the guide number may differ, since TTL spends part of the total flash power on testing pre-flashes. Mode high speed sync also greatly reduces the guide number.

Unscrupulous flash manufacturers use the confusion in measurements. I see a lot of Chinese flashes on the market, with a huge leading number declared. But if you look closely at the description of the flash, then most likely we will see that the guide number was measured at the maximum zoom position and at ISO 200. And worst of all, it is not known whether measurements were made at all, because the east is a delicate matter.


You need to be guided by the leading number very carefully.

Many amateur photographers want the most powerful flash ever. But why a powerful flash for a amateur photographer? And anyway, do you need a huge leading number? Take as an example SB-700. According to the instructions (without cheating, indicating the actual shooting conditions), SB-700 can illuminate at ISO 100 as much as 28 meters. Twenty eight meters! What can you shoot from 28 meters? In fact, 28 meters is available at f / 1.0. When the aperture is closed, the guide number will 'fall' linearly:

  • 14 meters @ F / 2.0
  • 7 meters @ F / 4.0
  • 3,5 meters @ F / 8.0 etc. (almost 4 meters if you shoot with the closed aperture F / 8.0!)
Distance calculation

Distance calculation. For ISO 100, the coefficient is 1, for ISO 200 - 1.4, for ISO 400 - 2, for ISO 800 - 2.8, etc.

For example, in my practice, most often I shoot with a flash of people at corporate parties, weddings, restaurants, birthdays, etc. And even once in my practice I didn’t need to shoot something at a distance of 28 meters. Even with 10 meters you have to shoot very rarely. In low light conditions, I rarely use ISO 100, my camera Nikon D700 does not have ISO 100 at all (only ISO Lo1). Even if you shoot 'from the ceiling and walls', there is enough power from any external flash. Moreover, all these numbers indicated in the description, in practice, simply disappear and do not play any role.

Flash power can play a key role, for example, when using external flash remotely using light-scattering devices - transmission umbrellas, soft boxes, light boxes, etc. In these situations, photographers really use the full power of the flash. Are you going to use the flash at full power?


A huge leading number is required very, very rarely.

Quite often I see 'bust' when working with an external flash. I often see (for example, in the registry offices) photographers who mercilessly 'fry' models with their flashes :). Often, shooting occurs at a highly clamped aperture value and at a minimum ISO value. In this case, the flash gives out its full power. And the burst of light from a flash at full power is not a sight for the faint of heart. Photographers who shoot at full speed with their flashes are popularly called '' welders', and their flash - with a welding machine. Indeed, the people who are photographed constantly see a very bright flash pulse that leaves 'spots' in the eyes. In such cases, I I recommend raising ISO and do not torment people. By the way, not only impressions about the photographer spoil from the welding type of shooting, but even the most resistant photographic equipment wears out. Flash lamps are especially worn out, glass on flashes can melt (they are plastic) and batteries wear out faster.


You need to learn how to shoot correctly with flash. Shooting at low ISOs is often not justified. Modern CPCs have a sufficient quality margin at high ISO. If you increase the ISO when shooting indoor with flash, you can simultaneously get rid of 'white faces against black walls'. Described in more detail in the section flash and high ISO.

A flash, like any other thing in photography, requires its own subtle approach. You need to learn to work with her, to study the features of use and their subtleties, and the crude techniques of the 'welding photographer' need to be changed.

General conclusion:

Should not be 'driven' by the flash guide number. The enormous power can do more harm than help. You need to know how to use fine flash settings to take good photos.

Like it. Thanks for attention. Arkady Shapoval.

Add a comment: Pastor



Comments: 45, on the topic: Flash power

  • Edgar

    Arkady, you did not indicate in what position the zoom sb 700 can illuminate 28 meters ...

    • Arkady Shapoval

      It’s logical that it’s strictly forward, because in this way you can get the maximum distance.

      ... flash output is measured at ISO 100 or ISO 200 and at the wide-angle flash zoom position and flash head straight ahead...

      • Edgar

        in the penultimate article, it would seem that there was a mention of Sat 900. Which supposedly could have broken 35m by 38mm (as I understand it, zoom). So after that I wanted to clarify what you mean

  • Alexander

    Usually the “welders” aim their flash at the ceiling and hit it hard. How justified is this?

  • pilotkins

    Yes, welders, they are ... welders :)

  • Alexander

    Good article. I completely agree with Arkady!
    I rarely use my SB600 at full power. In manual mode I often use about 1/8 - 1/16 power. And if I also take a high-aperture fix, then even 1/32 of the power is enough in the “shoot at the ceiling and walls” mode. So it goes.

  • Tatyana

    Very true noticed. I would like to shoot without a flash at all, but, alas, sometimes you can’t do without it.

  • anonym

    When I was engaged in advertising, I used this picture to advertise one desk))) The article, as always, is a class. And, on occasion, I want to say thanks to Arkady for the advice regarding shooting in the M and TTL modes on the flash.

  • anonym

    Thank you for a good review. My question is whether the auto mode (TTL) works if you send a pitch to the ceiling?

    • Denis


  • Denis

    I apologize for the tediousness, but in the phrase "since TTL spend part of the full flash power" IMHO, a soft sign in the word "spend" is superfluous

    • Arkady Shapoval


  • Kostya

    As always a very good article! Since I don’t have a good external flash, I’ll tell you about the experience of using the built-in flash (Nikon D90 camera). I always use in manual mode approximately 1/128 of the power (or more if necessary) just to extinguish harmful shadows from the sun or other light sources. So this power is always enough for me, and once there was even something remarkable.

  • R'RёS,R ° F "RёR№

    Thanks for the article. I'm going to buy something for the D3100, I decided to stick with the SB-700. After the review, I understand that I won't "shoot" the crowd and just a little is enough.

  • Jury

    “Even when shooting 'from the ceiling and walls', the power is sufficient from any external flash.”
    Well, I wouldn’t say that. Have you tried shooting in a huge and darkened audience?
    With us, only Sigma with the declared leader in 60m was able to normally expose everything from one wall.

    • Lynx

      let's go right away for shooting in complete darkness from the mezzanine in the hall of the Bolshoi Theater of the shoulder portrait in the back of the stage against the backdrop of the latest scenery.
      What is the little things?

  • Terms and conditions

    Outside, in bright weather, you often need full power, given that high-speed synchronization is almost always used. I'm not a pro, maybe I'm doing something wrong :)

  • Ilya Shakirov

    I slightly disagree with the author, who concluded that HF ​​is not particularly important. After periodic repairs of equipment, all masters advise not to shoot at maximum flash power. Apparently, the greatest wear and tear occurs at high capacities. And the work of any reportage photographer is a big wear and tear. I shoot this almost every day, I only use the flash indoors, and even then rarely, and not on the forehead. when shooting at the ceiling, well, this is not a power of 1/64, it is rather 1/8, / 4 and higher. If you do this on sb700, the wear will be higher than 900. Fewer frames in a series (don't say that series are not needed, they are still needed). For the sake of HF, I personally am ready to sacrifice functionality, but take something like the 76th Metza. And to lift the ISO up to 2 thousand and above in order to regret the lamp or the model is sometimes completely stupid, because in most cases the photographer is required to have the quality of the photo, and not the comfort of the “victim”

  • Stas

    Thanks a lot! The best photo business blog site. I constantly go out to him. This article helped determine the choice of flash.

  • Andrey Super

    I rent periodically in a darkened room without windows (a club), the hall is small, even rather small, a flash Sigma leading number 61 !!!
    I put a maximum on the flash and with full afterburner, and ISO 400 and oh how do I lack power!

    • lech

      I would like to know what kind of Sigma. by chance not 610?

      • Andrey Super

        Incidentally, she is the most Sigma EF-610 DG Super.

  • lech

    looked at the parameters of this Sigma. it turns out like Nikon-910, only three times cheaper.
    I wonder how Sigma works? on some forum I read that the menu is a bit confusing. it’s also interesting to know how constant the impulse is. that is, is there a large spread in the strength of the breaths with, say, a certain chosen parameter. and does it even make sense to take Sigma instead of the native Nikonovskaya.

    thanks in advance

  • ars

    everyone has their own approach and manner of shooting and different requirements ... but I have not met photographers who shoot in the forehead with sb-700 and raise the ISO, sparing the lamp or paying attention to everyone ... crap and nonsense! In most cases, the opportunity to use diffused, bounced light is always sought. In rooms with low or poor lighting, high ceilings and dark walls, for the best result I always go with the METZ-76 “hammer.” And with high-speed synchronization, the 700 is not a fighter at all ... and not for these purposes, it is so-so, perhaps -to gently illuminate for amateur needs or on the pupils with direct aim to give from 12 meters at the maximum.

  • Sergei

    I read a lot of things about outbreaks, opinions are diametrically different. Some say that the more powerful the puff the better, others say that a little power is enough. How to choose the right Sb 910 or stop on the SB 700?

    • Pastor

      If for work, for frequent photo reports under adverse conditions, for filming in large halls and for frequent weddings, then sb-910. If for amateur purposes, then the SB-700 is enough with the head.

  • Mitiai

    I would like to see the photos taken with the sb-700 very late in the evening at a distance of> 10m, provided that there is a working video wall behind the subject ...

  • Lina

    Can I ask you for advice? I have a Nikon D 7000. I want to buy a flash for taking portraits (beauty) at home. The purpose of the photo is to convey a clear and bright makeup. The budget is not big, because of this I think about Speedlight SB-300. Do you think it will be enough? Thanks in advance for the answer)

    • Pastor

      Considering the staggering ruble price of the new sb-300, I'd rather take a used sb-700. And the power is higher and there are more possibilities for working with light. Well, purely my opinion regarding the makeup shooting. I'd rather save even more and take two manual flashes - for example, Jungnuo 560-3. Power in such shooting conditions can be easily set manually. Arrange the flashes on both sides (try at different angles) to get a more voluminous photo, hold down the aperture to get maximum sharpness. Sat-300 for what it is necessary at all I hardly understand. For a non-poor and lazy amateur, most likely who are too lazy to carry a large flash and who will not turn their flash head. But the Jungnuo type 560-3 was created the other way around for poor and non-lazy photographers who are interested in working with light by hand, rather than hammering in a machine. But these are just my thoughts, if you need to take a couple of photos quickly and run on, then without automatic flash it will be tight.

      • KalekseyG

        Well said. An additional "little thing" on top of the carcass will not help, you need 1 or 2 normal ones, even if manual

        • Valery A.

          Why a trifle will not help? I put sb400, the direction to the ceiling, on it a homemade reflector forward (with an area of ​​a couple of matchboxes) and a stable and satisfactory result in TTL. True, the orientation is only landscape. And you push the girl to a deep study of the materiel, it may be better for her to comprehend consistently.

          • BB

            The flash mounted on the camera gives almost no volume.
            To draw volume, the flash needs to be pushed back a certain distance.
            Yes, a diffuser card is not bad for quick shooting, but for good soft light you need a larger illuminating surface - at least 30x40, preferably 50x70 for a front or chest portrait.
            I really don't like the square glare in the eyes, the rectangular one is tolerable + the rectangular softbox turns out to be a little more compact, convenient for small rooms.

            • Valery A.

              You are right, of course, but I do not create voluminous portraits, but a home (or non-domestic) reportage, if only the pictures are clear and colorful.

              • BB

                The question was not about the report:

                I want to purchase a flash for shooting portraits (beauty) ...

                In my opinion, in order to convey the "quality of makeup", lighting should emphasize the volume.
                There was no talk about the report, there are completely different requirements)

    • Alexey

      Yongnuo YN685 Wireless TTL Speedlite
      Yongnuo YN-568EX Speedlite
      the price is about $ 100.
      Nikon smokes nervously on the sidelines)))

      • Lina

        Thank you.

    • anonym

      And YOU by chance are not the Lina who is hiring a retouch?

      • Lina


    • lech

      at least two sb-700s are needed. on one softbox as a drawer, on the second grid as a control one. this is the absolute minimum with which a portrait really begins to be called a portrait and not just a memory photo.

  • lech

    To make portraits of black people without additional lighting is generally an empty number. On this profile picture, the power of the softbox was higher than the required one, I also put one grid behind my head (later I needed to put two grids). If the model was white and with blond hair, then with the same settings, everything would go into overexposure.

  • Denis

    “14 meters @ f / 2.0
    7 meters @ F / 4.0
    3,5 meters @ F / 8.0, etc. (almost 4 meters when shooting at a closed aperture of F / 8.0!) "

    It seems to me that you have a mistake, the aperture limits the light in half in the footsteps of 1.4, 2.0, 2.8, 4.0, 5.6, respectively, if 14 meters at 2.0, then 7 meters at 2.8, and 3.5 meters at 4.0, etc.

    • Michael

      The aperture limits the light in half, and the guide number is the distance, not the flash output. Everything is written correctly, there is no mistake. If we want to double the guide number, we increase the exposure by 2 stops.

    • US6IBD

      In general, I think that one should not operate with such a term as "changing the leading number". Guide number is a conventional value for comparing the power of different flashes. Like the number of "parrots" when comparing the performance of computer graphics cards.
      Under equal standard conditions, it is easier to compare different flash models: ISO-100, F / 1. And under these conditions, we get at what distance the object will be normally lit. The truth is not taken into account when comparing that flashes have a different zoom.
      Another example is the fuel consumption of a car per 100 kilometers. From here you can calculate how much gasoline you need at least 50 km, at least 1000.
      Therefore, there is no need to talk about changing the guide number. It sounds something like this: "How will the fuel consumption change per 100 km if I drive 1500 km?"
      And regarding the linear change in the distance to the number F, Arkady was not mistaken.
      If the distance to the object changes by 2 times, then the area illuminated by the flash changes by 4 times. Accordingly: when approaching, the illumination increases, while moving away, it decreases. So it is with the diaphragm - a change in the linear size (diameter) of the "hole" changes the amount of transmitted light by 4 times.
      Therefore, it is true: at F / 1 - 60 m, at F / 2 - 30, at F / 4 - 15.

  • Vyacheslav

    Well, a larger guide number, in my opinion, at least allows more economical use of batteries. Well, I think so. Since puffing more often will have to be incomplete.
    Secondly, a larger HF will extend the lamp life. For the same reason.
    Well, if you puff into the ceiling, then a larger leading number will “break through” the greater height of this very ceiling. Maybe HF is not an end in itself, but all other things being equal, I would get a more powerful flash. Yes, and acquired.

    • BB

      About battery consumption - by (rather, on the contrary - more powerful impulse - more consumption) :)
      Other things being equal, for a light pulse of a certain “light power”, you need a precisely defined amount of electricity divided by the efficiency of the electrical circuit. About the lamp resource - most likely yes. If the lamp is rated for more power, it is more likely to live longer. Although in inexpensive studio cameras the lamps for 200-300-400 joule flashes are the same, I don't know about on-camera ones.

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