getting the most power from your flash / speedlite / speedlight

getting the most power from your flash / speedlite / speedlight

This might be obvious, but the most power (or light) that you’re going to get from your flash, is at full output in manual. Then the flash dumps everything it has. Full power. You could of course zoom your flash-head a little tighter and get more power / range, but essentially, you’re at the limit.

This is useful to know when you’re balancing flash with bright sunlight. With this portrait of Shawna, out on the Las Vegas strip, I wanted that sun-flare look … but I also wanted to balance the super-bright background with flash.

working with direct off-camera speedlight

Since we were using only a single speedlight, a softbox wouldn’t have worked. The softbox cuts down too much of the flash’s output.  So we used direct, unmodified flash. But we used it off-camera, instead of on-camera, so we could get more interesting light than direct on-camera flash would’ve allowed.

The technique here is essentially the same as when we photographed Shawna earlier on, inside the hotel room, using on-camera bounce flash. (See: bounce flash portrait – a consistent technique )

  • find your background that you’d like to use in the image;
  • since we’re using flash in very bright light,
    we’ll be at our lowest ISO, and using maximum flash sync speed;
  • now we just have to find our aperture to give us correct / good exposure for the background;
  • now, for that aperture, find the distance for which the flash (in full manual output), will give you correct exposure.

That last sentence there might need a bit of explanation:

Manual flash is controlled by 4 things: power, distance, aperture, ISO

Of those 4 things,
– we have our ISO (lowest ISO since we’re in bright light);
– we have our power … full manual power so have have the max output!
– aperture … how we want to expose the ambient light
 – we now need to find the appropriate distance! 

Fortunately, most of the larger, better speedlights will show the distance for that aperture / ISO combination.

With this image above, our settings were:
1/250 @ f10 @ 200 ISO
(since this is the Nikon D3s I was shooting with, and the base ISO is 200.)

for the Canon 5D mk2, the equivalent settings would’ve been:
1/200 @f8 @ 100 ISO
(With Canon D-SLRs, the base ISO is 100.)

With the off-camera Nikon SB-900 and SB-910 speedlights, you could go into the menu of the flash to set the ISO setting, and read the appropriate distance for the aperture you enter. But that’s a mission.

With the Canon 580EX II speedlite, there isn’t a way to directly set the aperture and ISO readings on the flash. Sure we could calculate this from the flash’s guide number … but that too is a mission.


a quick method to calculate which distance to keep your flash

With that off-camera flash ON your camera, (so it can read the ISO and aperture you set), look at the scale at the back of the flash.

Note that I kept the flash zoomed to 50mm. So for full power from the Nikon SB-900, at 200 ISO, I have to be 13 ft from my subject for the flash to deliver f10 worth of flash.

For the Canon 5D mk2 equivalent, the display would’ve looked like this on the Canon 580 EXII speedlite:

Again, for 100 ISO, I have to be around 20 ft from my subject to get correct exposure for f8

The 580EX II only displays the aperture setting when the flash is in E-TTL mode. It’s an odd quirk.

Don’t make too much of the difference in distance shown here. The Canon speedlite’s display is more ambiguous about the specific distance. Also, the various manufacturers tend to be slightly optimistic about the output of their flashguns. So you DO need to check the back of your camera to see if your exposure is correct. Or close enough to correct.

That’s the process … find the aperture you need for your ambient exposure (at max sync speed and lowest ISO), and then for that aperture, find the distance on your flash when set to full manual output. Simple, really.

Now, shooting against the bright sun like that, all cameras will hesitate in their focusing. ALL cameras. What I do then, is rely on the depth-of-field of shooting in the f8 to f11 range as in this case, and then I focus on my subject’s feet.

No strong back-lighting to contend with, and I can lock my camera’s focus … and then get the shot.


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45 Comments, Add Your Own

  1. 1Jerry says

    Great tip about focusing on the feet, since you have a small aperture. I’ll have to try that. I’ve always just fought with it or gone to maual focus. Your way is probably better. Thanks.

  2. 2 says

    Great tutorial, as always!

    A few questions/comments:

    Did you use a full CTO cut here? Setting sunlight is very warm, and it looks like you’ve matched temperatures well here. But the CTO eats about a stop of light, no?

    Setting focus on the feet and shooting at f/8-f/11 is a great workaround for any issues that crop up due to focusing into a strong backlight (i.e. the sun). Of course, this does eat a lot of flash power.

    Also, 20ft (for correct exposure at ISO 100, f/8 with the 580EXII) is a very large flash-to-subject distance, and is contributing to the hard light you’re getting here

    With these points in mind, would the following have worked?:

    – f/5.6, 1/200, ISO 100 (one stop of extra flash output)
    – 580EXII at full power, 10 feet from the subject (2 stops of extra flash output vs 20 ft)
    – take the extra 3 stops you’ve gained and soften the light with a softbox or umbrella

    As long as you’re back far enough, f/5.6 should give you sufficient DoF for your “foot focus” trick to work (totally stealing that idea, BTW), and your light would have been much softer (assuming that’s what you want).

    Just curious. Great post, as always.

  3. 3 says

    No gel was used.

    I’m not sure why the jump from f8 to f5.6 would give you an extra stop of flash output? I’m not following your reasoning there.

    Also, keep in mind that the values here for Canon was something I worked out afterwards for explanation here, so I wouldn’t fixate too much on it that it would’ve actually been 20 ft in practice.

    It’s the thought-process here that matters, rather than the specific values.

    Neil vN

  4. 6Matt Carr says

    Neil, great tip on the “foot focusing”. I’ve been following your blog for years and even when you’re re-hashing well worn (to me) topics, there’s always a new little gem of an idea embedded in there.

    Your description about how to find the distance was something I hadn’t given much thought too. I certainly would’ve halved the distance and left my speedlight on 1/4 power to conserve my AA’s. And the process of “finding the distance” would’ve been trial and error. (pixel’s are cheap). It’s a good exercise to know how to get all the info up front from your equipment. Keep up the good work!

  5. 7 says

    14 ft isn’t particularly far. We were a group of 4 people shooting, so the extra working space helped.

    Even if working alone, I’m not sure I’d hold the flash only 6 ft away from the model. I would get the flashgun itself in the frame. I need that distance to get a clear composition.

    Neil vN

  6. 8Kevin Deibert says

    So the room for focus error @ f/11ish is that small that you are able to focus on the feet and recompose for the head? I’m assuming that has to do with the distance to the subject as well, correct?

  7. 10 says


    Opening up from f/8 to f/5.6 increases the flash (and ambient, of course) exposure by one stop (i.e. you can lower the flash power to 1/2 OR possibly add a modifier, and still get the same flash exposure). That’s all I meant.

    I was just thinking of ways that would have allowed you to use a modifier, and thus get softer light. Opening up to f/5.6 and/or moving the flash closer to the subject are two possibilities.

    Interesting that you didn’t use a gel.

  8. 11 says

    Mike .. the entire point of this post was to shot a consistent technique for adding the most flash you can, to very bright light. Changing the aperture to let the background blow out more – well, while that is a technique, and the photo might look as interesting – that isn’t what we’re chasing here. You’re describing a different scenario by breaking down the numbers there like that.

    I don’t want to use a gel here (such as a 1/2 CTS), because I don’t want to balance my flash with the warm ambient light. Since the flash is colder, the background would appear warmer. Gelling would’ve reduced the warm tones in the image.

    Neil vN

  9. 12 says

    Dumb question: How do you lock focus?

    1) Hold the shutter button halfway down while focusing on the feet and recomposing the image?
    2) Something else? (FV lock button? – I never used this button before).

    This article and other like it seem to show that one doesn’t need a lightmeter to get started on manual flash. The shortcuts are enlightening.

  10. 14Kevin Deibert says

    One more question Neil,
    As far as the distance settings, would you say its fair to assume that you can apply this to bounce as long as you “guestimate” the distance from flash to bounce and then add that distance to the subject?

  11. 15 says

    Bounce flash is a little more involved, since you lose light depending on how reflective the surface is that you’re using.

    So it would be way too much work to do the actual calculations and then derive the aperture / distance combination.

    Just use TTL flash when it is the congruent scenario to use bounce flash.

    Neil vN

  12. 17 says

    Perhaps, perhaps. But that wasn’t an option here. Since we had one model, and one speedlight … but some were shooting with Canon and others with Nikon.

    I wanted a universally applicable technique. And this is it.

    So we used PocketWizard Plus II units to trigger the speedlight.

    Neil vN

  13. 18Carlos A says


    There are several ways to “lock focus”. One is to set up your camera to do exposure only on half-press of the shutter button and assign a different button to do focusing… this is easily done on the Canon 5D MkII (and I suppose also on the Nikon). That way you can focus with one button and unless you press that button again, the focus will remain “locked” to the prior value.

    If this is not possible on your particular camera, then I would simply focus on the feet with the shutter button, then simply move the focus switch on the lens from AF to MF so that the focus point wouldn’t change.


  14. 19 says

    Hi Neil,
    I have a question about this sentence from the post :”Now, shooting against the bright sun like that, all cameras will hesitate in their focusing. ALL ”
    ->does it mean that the focus in bright sun light is wrong ? So a portrait in bright sunlight at f2.2 for instance is more difficult in bright light condition?
    And, a side question, is focusing a subject at f2.8 or wider all the more difficult when the distance to the subject is increasing?

  15. 20 says

    Ced … cameras tend to hunt in their focusing. So much that they often can’t latch focus. And when they do, there is a chance that the image is mis-focused. Try it.

    Re your last comment, DoF becomes greater, the further your subject from the camera.

    Neil vN

  16. 22 says

    That tip to focus on the feet is gold! Thanks!

    I’ve just finished reading Bryan Peterson’s book on flash and he goes on about how easy it is to use manual flash just as you described, by consulting the display on your flash. But what if you’re using an older/lesser flash Iin my case, the SB600) that doesn’t have the flash distance guide? Is there a chart somewhere or something I can print out? A website? An app? I don’t want to upgrade to an SB-700 or 910 *just* for this feature.

    And thanks for your tutorials — I’ve been reading for a few months and learn something every time I come here. :)

  17. 23 says

    Yes there is. It’s called the Guide Number of your flashgun. Learn to love it if your flash doesn’t display distance or if you don’t own a lightmeter.

    Neil vN

  18. 24 says

    Right, but how can I transfer the guide number into the ISO/shutter speeed/distance equation? The only place I haven’t looked is in the flash manual. Sorry if this is a dumb question, I’ve been stuck on this for weeks!

  19. 27 says

    Hi Neil,
    Ugh! Why did I write FV lock? lol It’s funny that I wrote about the AF-ON button later. But it looks like you didn’t need the AF-ON button for this photo. In that case, I should do what I have been doing previously. :)

  20. 28Matt says

    I always learn so much about staging the model and the equipment from your “pull back” shots. Do you have one for this image that you’re willing/able to show us?


  21. 30Ray says

    I was there! I learned so much in the short time together. I love how you keep everything simple. Thank you Neil!

  22. 31Eduardo B. says

    Hi Neil,

    Could you please tell me if you noticed any improvement in the new SB-910 regarding the thermal cut-off?
    What I hear is that the new thermal control only slow down a little the flash in order not to shutdown. I would like to know if the SB-910 can handle betther a massive usage with the thermal cut-off disabled.


  23. 35Dany says

    Thanks Neil for your great explanation !!
    As every one say, you give very clear explanation !!
    Merci Dany

  24. 36Catherine says

    Hello, Neil! Thank you very much for your work! I love your articles very much, there were very helpful when I started learning flash photography, I come back to them regularly. Is it possible to ask you for a permission to translate some of the articles into Russian and to publish them on my website with a link to your websource and any other information you wish?

  25. 38Gavin says

    Ok, I don’t want to sound like a creeper, because I’m not… but I’ve never fallen in love with a girl through her portrait before :-)

    And thanks for a really great post. I’ll be using your technique tomorrow at the beach!

  26. 40Cam says

    I have both a Metz 58 AF-1 and a Canon 580ex II. They appear to have the same GN. For the settings you provide in the example (ISO 100, f8), the Metz – which does provide distance info on its LCD panel without needing to be attached to the camera – it says 17 feet. That seems like a fairly wide margin of error, so I’m assuming the Metz will have a tendency to overexpose if one follows its distance numbers?

  27. 41 says

    The difference between 20 ft and 17 ft is incremental in terms of your flash exposure.

    Also keep in mind that the Canon speedlite’s display isn’t marked in fine discreet values. Ultimately though, I don’t think it will make much difference.

    Neil vN

  28. 42 says

    Thanks for this Neil. I’ve been struggling with balancing flash and ambient, and how to determine where/what I’m metering for, then adding flash. After reading several of your articles today…and re-reading certain points (lowest ISO, highest shutter (sync) speed then adding flash to balance) it seems so much clearer. Can’t wait to get out and try it all out tonight.

  29. 43 says

    So Neil, you have been my mentor on flash photography. I have learned so much from you. But I have a really dumb question. How do you measure distance? I have viewed distance guides with mistrust because I am not sure what the difference between 12/15/20/30 feet is. Do you have a method?

  30. 44 says

    If you consider 6 ft to the the height of an average man, then it becomes easier to judge the distance by imagining people lying on the ground, feet-to-head. 6 ft / 12 ft / 18 ft / 24 ft.

    Ultimately, the exact distance isn’t that of a big deal, since you are going to adjust your flash / aperture by looking at the results of a test shot or two.

  31. 45Darren says

    Great article Neil, I have always wondered how to use the distance scales on my SB-26’s. I can only run them in manual as no TTL with these on a DSLR, even when on the camera. Using the distance scales makes that first exposure so much easier to work out. I can then just tweak to taste.


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