Lighting 101: Balancing Flash and Ambient, Pt 1

Editor's note: To understand balancing flash and ambient, you should have a good, basic understanding of f/stops and shutter speed. That stuff can be found in lots of places (Google it) so I am not going to totally restate it here.

F/stop, Shutter Speed and Flash

While f/stop and shutter speed both control exposure, for our purposes it is important to know how they do so differently. Shutter is a time-based control. F/stop is a diameter-of-the-lens-hole based control.

Since the light from your flash is pretty much instantaneous, it really does not care about the shutter—as long as you are at or below your camera's top "sync" speed. Which for most cameras is either 1/250th or 1/200th of a second.

Note that there are fancy, flash-pulsing methods which will allow you to sync at higher shutter speeds such as 1/1000th of a second. But (a) they have their drawbacks, and (b) getting into that now would be needlessly complex. So just set that aside.

Two Exposures Happen at the Same Time

Every time you take a flash photo, you are making two exposures simultaneously. You are making an exposure of the ambient light, and an exposure of the flash's light. Whether you take this into account or not, it is happening every time.

The ambient exposure is controlled by the f/stop and the shutter speed. The flash, being instantaneous, is controlled by the aperture.

The photo up top is a good visualization of the fact that two images are being made at once. The shot of Robert, a soldier in the U.S. Army, was made with a slow shutter speed. But I also included a flash, which happened instantaneously and froze Robert irregardless of the shutter speed:

Think of it as two overlaid exposures: Frozen, instantaneous flash exposure, mixed with a slow-shutter-speed ambient exposure. Both are made at once, and both light sources are additive to the exposure.

So you have two exposures to consider in every flash-lit picture: the ambient and the flash. I like to find my ambient exposure first—nothing fancy, just trial and error. Once I have that exposure (in which, remember, the shutter speed must be at or below my camera's sync speed) I have a starting point for my final, lit image.

Next, I'll "dial down" my ambient exposure. This means nothing more than changing my camera's settings to underexpose the ambient. How much? That's your choice. And it will determine the contrast range in your final, lit picture.

Remember, when you move your flash off camera, the difference in location produces shadows in your image. That's what makes your subject look all cool and 3-D. And the depth of your shadows—your contrast range; your drama— is determined by the underlying ambient exposure.

Let's Give This a Test Drive

Below is a portrait I shot of Jessie, a local social media entrepreneur. We are going to use a second flash here, to light the background. But the light balancing principles are exactly the same. They work whether you use one flash, two flashes or a hundred flashes.

Okay then. Let's get her in some shade first, because it's much easier to balance a small flash indoors or in shade rather than competing with the full sun. (But we'll get to that next post.)

Here she is, exposed for normal ambient light in shade:

The exposure here is f/5.0 at a 1/160th of a second. For the record, we are at ISO 200 on the camera's overall sensitivity setting.

It's okay, but kinda "meh," right?

So before we even add any flash, let's crank her down a little bit and create some "drama" in our final image. I am going to close down my aperture and drop her by a little over 2 f/stops. So I am going from f/5.0 to f/11. Nothing else has changed:

Exactly what you'd expect, right? Everything is darker. But there is still legibility everywhere - no big black areas. This legibility is important in the final image. Also, notice that since we closed down the aperture we now have more depth of field and the wall in back is now more in focus.

We have created a "safety net" of darkened ambient exposure. When we add flash, no part of this image will get any darker. So we'll end up with drama PLUS legibility.

Now, let's bring in our flash. (Flashes, actually.) We work with manual flash—for predictability and repeatability. One less variable to screw up. And because of this, adding the right amount of flash exposure to a photo is simple and straightforward.

I'll bring in a flash, on manual power, in an umbrella positioned out of the frame and from camera right. Take a test shot. If the flash is too dim, I'll turn up the power. Say it was at quarter power (on manual, as nearly always) when I made my first frame. If too dark I might turn it up to half power. Or vice versa if it was originally too light.

Also, I am going to do the same thing with a second flash back on the wall. Just to make the wall pop a little bit. And here is the result:

Wow, right? Same exact spot as the first shot above, which was properly exposed open shade. Then we dropped down that exposure to get the sort of "safety-net" ambient-only exposure. Then we lit Jessie (and the back wall.)

This, in a nutshell, is balancing ambient and flash. Everything going forward with your lighting kinda hinges on you getting this. So if you don't understand it, re-read it and stay with it. But be aware that it may not really make sense until you get out there and actually do it.

When working this way, I like to think of my flash as a main (or "key") light and the ambient as my supporting (or "fill") light.

The Process, in steps:

1. Get a full ambient exposure.

2. Drop the exposure down to create a little "drama." How much, is up to you.

3. Bring your subject back up to full exposure by adding flash.

It's Almost Not Fair

How often have you heard this, usually with a tone of superiority:

"I am a purist, I only shoot available light."

(Translation: I am scared shitless of flash.)

As an ambient light photographer, you only have one "correct" exposure. Maybe a little wiggle room if you are being interpretive.

But as a lighting photographer, we control everything in the frame, independently of the other areas, by how and where we expose and add light.

I have been doing this for almost three decades, and I still think that is the coolest thing ever. If you want more detail on the Jessie shoot, it is laid out in more detail (but also assuming a little more knowledge) in the On Assignment section, here.

Otherwise, let's flip the process and use flash to control the harsh shadows created by directional ambient light. Same process, just backwards.

Next: Balancing Flash Intensity With Ambient, Part 2


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Blogger CHPhotographer said...


Second, as a wedding photojournalist, "seat of the pants" shooting is my life. I go for emotion, expression and rarely check for exposures during the day. But I do have those formals to take and where I once disliked having to use "artificial" light, I now love the stuff--and I have David and this site to thank.

As for the previous post. This 101 section on balancing is the key to the entire game, the whole enchilada, or at least your basic beef enchilada with a little extra sauce on the side. Pardon the 60's slang but if you don't get what David's layin' down, then keep reading it until you do. It will come, I promise. Just keep at it and have faith in the wisdom and levity that David is imparting upon us. Are you still reading this? Stop and reread Pt1 again. This isn't brain surgery. If it was my malpractice insurance would be around six-figures a month.

Thanks David!

August 04, 2006 2:57 AM  
Anonymous Anonymous said...

Would it make sence... calculate the exposure using your camera's reflectance meter and dial in to -2ev then adjust the flash accordingly? Might save guessing the normal lit room.

November 09, 2006 9:35 PM  
Anonymous dw said...

So, you calculate the exposure, drop it a couple of stops - but how do you initially determine what intensity you should fire your flash at? 1/1? Or is it a crapshoot?

November 24, 2006 4:06 PM  
Blogger SoniaK said...

It's a crapshoot.

Till you get some repeat experience under your belt.

January 06, 2007 11:41 PM  
Anonymous Anonymous said...

I am struggling to understand using flash in social events mostly at nite indoors. I just came across this site and so far looks great. I have a fuji s2 and SB-28 flash light. I used to put the camera in P mode(auto) but results were not consistant. I want to learn real techniques of knowing how to calculate and adjust my camera/flash in quickly changing situations in social events.
so far i love this site. hope i could post more specific questions in the future and get answers. Thank you david.

April 15, 2007 1:21 AM  
Anonymous Anonymous said...

Yesterday I had my girlfriend volunteer for some test shots. The sun was very hard and it was late afternoon so it had some direction (would be classified as hard light), which meant she had some very dark shadows on her face (mostly under her nose). The sun was hitting her 30 degrees from the left.

Now I used my new knowledge from strobist and unpacked my on-tripod flash and placed it on the ground. I put the bare flash on manual and placed it to her right. I now suspected that the flash would bring up the shadows, but instead I got a whole bunch of shadows with various light levels, ranging from darkness where neither the sun nor the flash had hit to very bright where both hit. Furthermore, other shadows where either the flash og the sun had hit. Both light sources being small giving strong defined shadows did not make her look very good and the light seemed very unnatural. I doubt it was a ratio problem, since the shadows are brighter where it actually hit - looks more like a fill-flash positioning problem, maybe combined with both key and fill light being small light sources?

Please help me before I start thinking that fill flash would be better on-camera as the author writes on the link below :-)
"Why side fill is EVIL"

Thanks for a great site
Henrik, Denmark

April 26, 2007 10:17 AM  
Anonymous Anonymous said...

In order to understand flash photography, I been reading "Flash, the most availble light" book by Quest C. Couch. I have understood few things but still there are many things that confuse me. I hope to get them aswered here.
I understand the relationship of f-stop and shutter speed for a given ISO/film speed for exposure. But when
flash is added to the equation things become confusing. From the above mentioned book, I have understood the ambient light exposure is controlled by shutter/f-stop for a given iso. so far no problem; and flash exposure depends on f-stop and flash power and distance of flash to subject.
here is my problem; In the book he used an example that lets assume ambient exposure is f/8 and shutter 1/60. To set the flash one stop less the ambient for fill he says...set f-5.6 on the flash and leave the f-8 and 1/60 on camera. I dont understand how setting flash to 5.6 will drop flash to one stop less that ambient exposre. I really think, I dont understand how Flash exposure depends on aperture. Help.
thank you

April 28, 2007 5:10 PM  
Anonymous Anonymous said...

By setting aperture on the flash, what does really happen? Is there a aperture openning on the flash unit thru which light is emmitted Or is it a way to correspond to the aperture set on the camera lens. What happens when camera and flash are both being used in manual mode and camera is not telling the flash what aperture is set on the lens.....can bothe apertures( cmaera and flash unit) be set at different values? If my basic quesions get answered here may be rest of the mystery will resolve for me. I hope some one here will help me out here. Thank you.

April 29, 2007 11:20 AM  
Anonymous Anonymous said...

i guess not!

April 30, 2007 1:54 AM  
Anonymous Thomas Pickard said...

Hey anonymous,

I don't know if this helps, but when I am thinking of lighting and ratios I nearly always think in terms of quantities of light. I then adjust f-stops and shutter speeds accordingly.

If I am reading your post correctly, the book you are reading has the camera set to an ambient exposure of f8 at 1/60 and what the author wants to do is to use the flash as a fill light on the scene Thinking in terms of quantities of light, the fill light is a light that has to provide less light than the ambient scene - otherwise it would blow it out the ambient exposure.

So if the flash was set to f11 what would happen?

The flash would over power the ambient light because the flash is producing too great a quantity of light when compared to the ambient exposure.

If you had the flash at f8 (the same as the camera setting of f8), then the scene will look similar, all things being equal).

If you had the flash at f5.6, the flash will produce less light than if it was set at f8, thus producing fill light and balancing with the ambient exposure for the scene.

The best way to get a handle on this is to practice it. Find a scene, determine the ambient exposure (try for the same specs as your book camera on f8 at 1.60, just bump the ISO up) and put a subject/object that could do with some fill.

Now set your flash and take four frames:

1. Without the flash

2. With the flash set to f11

3. With the flash set to f8

4. With the flash set to f5.6

When looking at the results, think in terms of quantity of light being put out by the flash. After all, what you are doing is balancing light sources.

A fill light set to f5.6, with a main light (or ambient light) set to f8 is a 1:2 ratio assuming the shutter speed remains constant. When the aperture is set to f8 you are getting twice as much light as when the aperture is set to f5.6. So by stopping down the flash (or fill light source) to f5.6, you are effectively halving the available light being produced by the flash, hence a 1:2 ratio.

If the camera was set to f8 and the flash to f4.0, you have 2 stops difference in exposure or a ratio of 1:4.

Just remember: think in terms of the quantity of light being put out when trying to balance light sources – whether that is ambient with fill or using two light sources with one light as a main light and the second light as a fill light.

I hope this helps. Thomas

May 14, 2007 3:49 AM  
Blogger Matthew said...

wow i think i have just had my mind melted and reformed into saving me time and $$. I have always wanted to buy a light meter but now I am soo glad that I can use that several hundred $$ to buy more flashes. Thanks

July 23, 2007 11:28 PM  
Blogger Steve said...

It may help to understand how the flash works. The flash has a maximum amount of light that it can produce and it can be set (manually or automatically) to produce from 0 to 100% of this maximum. Modern flashes also have a sensor that measures the amount of light reflected back at the flash. When you "set the flash for f/4", you are telling the flash: "My aperture is set to f/4, and I've told you (via a flash setting) what my ISO is, so crank out enough light to give me a good exposure at f/4." The flash calculates how much light is needed, turns on the flash, measures the light coming back, and cuts off the flash when enough light has been received. Notice that this assumes that the flash is located near the camera with the flash sensor pointing in the same direction as the camera---so that it sees the same light as the camera. Once you start moving the flash around, pointing it in different directions , etc., then this approach doesn't really work any more. TTL flashes use the in-camera light meter instead of the flash sensor and typically use a short pre-flash to determine the required flash power. Then the camera controls the flash (setting its power output). This (in theory) allows you to move the flash around, as long as the camera and flash can communicate. But all this auto flash stuff is like shooting in your camera's program mode. You're letting the camera do all your thinking for you and it sometimes makes mistakes. If you are inexperienced or rushed, this may make sense, since the camera's (flash's) decision-making is probably better than yours. But at some point you'll get better and more reliable results if you learn to set things yourself. The problem with automatic flash modes is that you will make an adjustment (after a test exposure) and the camera may also make its own adjustment---one that you don't know about (and it doesn't always know what you've done). Chaos results. I was tearing my hair out trying to get systematic results from my Canon flash until I finally realized that I needed to put everything in manual and adjust things myself.

December 20, 2007 12:29 PM  
Anonymous Anonymous said...

One thing all of you who are having trouble need to remember is that when you are using manual flash is that the f stop controls the flash exposure. Shutter speed controls the ambient light exposure.

For example, if your ambient light exposure is 1/60 @ f/8 and the flash is too hot on your subject you would close down your f stop to f/11 or more until the flash exposure is just right.

Now once you have the correct f stop set you change the shutter speed to control how much ambient light there is in the photo. Say there are windows behind your subject with daylight coming through them and at 1/60 of a second they're too overexposed for your liking. In this case you would use a faster shutter speed which will reduce the the amount of ambient light coming through the windows which will result in them being less over exposed.

Another ambient light example is if there is tungsten or florescent lights in your scene. At 1/60 of a second you may see a yellow or green cast from the ambient tungsten or florescents. If you increase your shutter speed to say 1/125 or higher it will reduce and/or eliminate the color cast from the tungsten or florescent lights.

Keep this in mind before trying to use the technique suggested in this article.

December 27, 2007 9:28 PM  
Anonymous Anonymous said...

Hi, great thread to learn from. One question - I have a SB-600 (bought it some time ago before I read this otherwise would have got a SB-24). I don't have aperture or ISO settings on the strobe, just a flash output setting going from M1/1-full output to M1/64 in which is the lowest output. Is there an easy way to guage where to start. Say my ambient no flash setting was 1/60 @ f5, ISO 200, is there an easy way of coming up with the initial flash output level setting?

February 27, 2008 3:27 PM  
Blogger Mike said...

Just foud your site and getting into lighting and this is a nice post Dave that kind of made it all make sense for me. But please tell me this designer guy that was the subject of the main photo was fictional???

March 04, 2008 4:48 AM  
Blogger Pepe said...

In response to: Any ideas on how to work the f-stops on a 430EX?

Using the ST-E2 you can control the f-stops. You also gain ETTL control with it. You will have a very nice sistem if you buy more canon EX series flashes.

July 02, 2008 9:03 PM  
Anonymous Dave said...

Great site...I have learned so much here...thanks! Anyway, my question is when using the flash in manual mode (off camera), what exactly does the zoom funtion do and how should I be using it and/or setting it? Again, thanks a bunch!


July 12, 2008 8:22 AM  
Blogger Pepe said...

Hi Dave:
Zoom function - off camera- is made to control the angle off the light, i.e. How far is your subject? How large do you want the light path (surface covered) And/or: how soft do you want the light? You can add more control using the rest off the controls in the flash for example: adjusting the +/- F stops in the flash controls.

You may experiment with the flash using all controls in manual Flash, Camera and finally Bridge or DPP so you open the pictures without auto control exposure – This last is my most common mistake when testing a flash-

Sorry for the Spanglish, I’m from Mexico City and haven’t type English often in a long time –last century-

July 12, 2008 12:55 PM  
Blogger Pepe said...

This liny may help a little:

July 12, 2008 12:59 PM  
Anonymous Nagaraj Pudukotai said...

For users of Canon strobes, there is a great website which probably is the single most comprehensive documentation on Canon flashes. In addition, it also helps you understand flash photography in general.



July 20, 2008 11:00 PM  
Anonymous P:DEeK said...

This article really helps me balancing the light; flash & ambient. At 1st test, it really works & and make me smile. Thanks for the info.

for those who confuse, make sure you familiar with the basic things & keep reading till u get what David try to point out.

October 01, 2008 10:48 PM  
Anonymous Anonymous said...

Really good post where the grey cells had to work LOL

I have read all the comments, and I don't know if this will clarify the F stop and flash relations.

Try to take a picture in a completely black room with a flash.
(in the following ISO is kept out of the equation for simplification)
Lets say you are taking a picture at 1/250 f8 flash set at 1/4 of max output.

Now the picture comes out under exposed one stop. What can you do? OK try to take the picture at 1/125, that should give a stop more light. If you tried you will be disappointed, because it will look the same. Why? because within the 1/250 of a second you already got all the power that the flash will give in one shot. After maybe 1/5000-1/1000 of a second it will not deliver more power.
Now try to F/5.6 and that should give you the extra stops of light, right? Yes it will.
We could also have dialed the flash up to 1/2 power with the camera at F/8.0, at that would give the same exposure.
If there where only flash the aperture or flash power would be the only way to change the exposure.

Now we bring in the ambient light! Since this is a permanent light source, we can control that via both shutter speed and exposure, and we do that every day when we take pictures.

Now we have the ambient light at 1/60 F/4. We want to underexpose 2 stops so that gives us the options: 1/60 F/8, 1/125 F5.6 or 1/250 F4.0 (plus a ton of other but these are the ones I will look at)

Now forget the ambient light for a sec and think about flash in the dark. If for instance F/8 would take full flash output for a correct exposure, what would the other F stop do?
F/8 = Full power
F/5.6 = 1/2 Power
F/4 = 1/4 Power

So if we wanted to run the flash, at half power we should use F/5.6, and since we then wanted the ambient at 2 stops underexposed, we should shoot at 1/125 F/5.6
Lastly if we wanted to run the flash at 1/4 output with the ambient 2 stop underexposed it would be 1/250 F4.

Which one should be used? That again depends of wanted depth of field, and how long it is OK to wait for the flash to recycle.

Hope I didn't just muddy up the waters.


January 11, 2009 12:21 AM  
Anonymous Anonymous said...

To the anonymous poster who spelled it out by advising to take the pics in a totally dark room with flash -- thank you! This completely makes sense now.

February 11, 2009 9:32 PM  
Blogger Ken Taylor said...

Okay, one more thing that I don't understand: When you're doing the metering for the room, does it matter that you're not spot-metering for the shadows? The reason I ask is because, depending on where your flash is going to hit, isn't it just going to white out the shadows anyway if you don't meter appropriately for them? Do you have to only control the flash's light to hit the subject and not effect the rest of the room? As well, if you stop down the aperture (and slow down the shutter appropriately), isn't that extra flash that you'll have to push out going to blank out the shadows too? I don't understand how, if you've got to dial up the flash power at any point, those original ambient shadows aren't going to get killed.

Thanks for the help!

February 12, 2009 2:54 AM  
Blogger Steve said...

To Ken Taylor:

Remember that the light from the flash falls off as the square of the distance (basically, the surface area of a sphere goes as the square of the radius). So, for example, if the flash wall distance is twice the flash-subject distance, then the wall will get 1/4 the light. Unless the wall is close (or much more reflective than the subject), it will usually be dark(er).

You see this effect when trying to take group snapshots in a bar or restaurant. Standing at the end of a table, the close people will get blown out and the far people will be dark.

February 12, 2009 8:44 PM  
Blogger Migs said...

I can't help but wonder where the flash meter gets introduced in all this sequence. It would certainly take the guesswork out of the game. Is it mentioned somewhere?
Thanks amigos! -Migs

June 08, 2009 1:12 PM  
Anonymous Jake Watrous said...

As a budding real estate photographer these pages, in particular this article, have helped me out a lot. The quality of my interior photos has jumped dramatically, all thanks to your suggestions.

I would love to take a photographic lighting course, but none of the community colleges in our area hold them.

To me, then, these pages have become a substitute course and, in my opinion, hold as much or more value. That you are giving this away to us all is amazing.

Thank you so much!

June 09, 2009 4:17 PM  
Blogger Migs said...


Santa Fe Workshops offers these courses on lighting. A bit expensive, but in my opinion of the finest quality!


June 10, 2009 8:17 AM  
Blogger Dave said...

The technique as described is totally trial and error. It assumes you have at least some idea of how to use your digital camera's meter and that you have a flash with a manual mode.

It might help to think about a flash exposure as a kind of double exposure: the flash exposes your subject and the shutter exposes the background.

How do you determine how much flash power to use? Start at full power (or the smallest aperture the flash allows). If your subject is blown out, reduce the flash's output or use a larger aperture. After a few practice sessions you'll be able to judge how much flash power you need.

July 09, 2009 1:40 AM  
Blogger Boy Wonder said...

Firstly, thank you David for your great site. It has supercharged my lost passion for photography.

One thing that i'm curious about and something that doesn't seemed to have been answered in the comments:

When using my SB-24 in manual mode, do the ISO and F-stop settings ON THE FLASH make any difference? They don't seem to.

Thanks again.

October 22, 2009 5:45 AM  
Blogger Isabelle said...

Hi David,
Thanks a lot for your great site. As you say, "what we want is repeatability". That is exactly what I've been trying to achieve in order to work with a smooth workflow and concentrate on composition rather than technicalities. I have a question though. I understand the setting for the ambient light with 2 stops underexposure. Now it seems the settings on the flash only rely on trying, looking and adjusting from what your LCD screen shows. So how did the photographers manage this with film cameras before? There MUST be a setting recommended for ur flash without having to check every two shots whether your settings are correct? Can you please advise ? Thanks a million

October 23, 2009 12:28 AM  
Blogger Isabelle said...

Hi David,

Thanks a million for your great site. I still have a question! I understand the setting for the ambient light with 2 stops underexposure. Now it seems that the flash settings only rely on shooting, looking at your LCD screen and adjusting. How did the film photographers do in the past? There must be a more scientific way to set your flash once and for all for this or that condition isn't there? As you say "we want repeatability", and this is what I am trying to achieve without tearng all my hair off!!
Thanks for the advice.

October 23, 2009 12:31 AM  
Blogger Migs said...


You can use a flash meter. That is the scientific way. My wife has both and she still eye-balls it. Eventually you learn to do it that way and forget the meter.


October 23, 2009 10:47 AM  
Blogger Lulu said...

I think I need outside help since I'm not sure why things turned out the way they did.
I was trying to balance ambient as fill with small, manual studio strobes acting as main light.
I had myself a correct exposure with the strobes at ISO100 and F5.6, 1/30s. I felt that the ambient was a bit too weak so I pushed ISO to 200 and then to 400 as I was working with moving people. I thought that the strobes would nuke the scene at ISO 400 but they didn't. Highlights were not affected as much as darks and midtones. I mean the ambient light filled just perfect, but the strobes did not seem to get that much stronger.
Why did it go this way?

December 02, 2009 6:18 PM  
Blogger holliwr said...

Help with "on the fly" flash shooting... I read and "kinda" understand what the article said, but...This weekend I was shooting my son's karate graduation. You have 30 seconds (or so) to walk up and take a picture before the next kid comes up. You DO NOT have time to shoot a few test tell me a good starting point for this kind of shooting, or how to deal with these conditions. I have a Nikon D700 and was shooting with the 24-70 f/2.8 lens and SB-900 flash (with a difuser on it). I took the shot on "P" mode, with flash set to "0" compensation. The shot was overexposed. Thanks for any help....Rich

January 25, 2010 10:21 AM  
Blogger Jim Coffey said...

Controlling the flash power without walking over to the flash...

As others have explained: the flash burst is instantaneous so you control the amount of flash light with the power setting on the flash, ISO, and the aperature setting on the camera.

0. With the flash turned off:
1. Set the camera to P mode
2. Set exposure comp to -2 (or whatever you want the shadows to be, I like -1 3/4)
Snap a test pic you should see some detail in the shadows, not totally black). Pick an ISO that gives you a reasonable fstop/shutter speed combo.
3. spin the shutter speed dial which will change the aperature/shutter speed combo but MAINTAIN the same ambient exposure.
1/60 F4
1/30 F8
1/120 F2.8

Snap some pictures to prove to yourself that this works. You should get the exact same exposure.

warning - watch for your sync speed on the high end and your blurry handheld speed on the low end. If you've picked your ISO properly you should have plus/minus a stop in both directions.

4. NOW - turn on the flash, set it to manual and about 1/4 power
bounce it, point it direct, umbrella, doesn't matter.

5. Take a pic - the flash is your main light. Look at the histogram.
If it's underexposed just roll the dial to shift the aperature/shutter combo, roll it the other way if it's over exposed.

6. voila - without walking over and messing with the flash you can now adjust the flash to ambient ratio.

November 18, 2010 11:27 AM  
Blogger Raw Restoration said...

In Jim Coffey's example above, the second example after 1/60 F4 should be 1/30 f/5.6, n'est-ce pas?

November 29, 2010 7:02 AM  
Blogger Rex-Rizza said...

i just watched onelight workshop DVD and came back to read strobist 101 again, now things start to make sense! i remember reading this blog maybe a year ago (new to photography, just got my dSLR) and my head was spinning.

1) shutter speed controls ambient light
2) aperture controls flash exposure
3) Flash power
4) Flash distance to subject
5) ISO

thanks for the 101,but this assumes someone already know a thing or two about how to set flash, exposures etc. before they can truly grab the principle. it's like a puzzle that you have to piece together after you read all the steps (101).

January 13, 2011 4:57 PM  
Blogger peter.ross18 said...

Great site - Having read through this and most f the comments there are still a couple of things I am not sure about. There is a lot of talk around setting the flash to a particular f number. Up until this stage I have only thought of f numbers in terms of aperture.

I have a Speedlight 580 II which I haven't used much yet. In manual mode it only seems possible to set flash power in terms of ratio's (1/1 to 1/128). Do some flashes allow you to set flash in terms of f stops?

How do I know where to start in terms of setting the flash power when I am working with ratio's?


February 17, 2011 8:01 PM  
Blogger Wesconi said...

After deciding that studio photography is boring and repetitive, I went back to my origins and began shooting models outside again, in all kinds of lighting conditions.

First thing I realized is that much of my work I formerly admired wasn't really that good, I fixed it in Photoshop.

Fill light is everything for swimwear and fashion / glamour shots. I mistakenly thought getting a $1000 fast 2.8 lens would make light balancing easier. After reading this post, and doing some text shots / experimenting I determined I was approaching balanced light the wrong way entirely. Thank You!!

Opening the aperature did help reduce the need for fill light but my DOF did suffer, and my white balance was barely acceptable.

Batteries be damned, I'm now using higher stops with the same 1/160 shutter speed I prefer.

I found this blog because I just bought some cheap strobes / light stands so I didn't have to carry out my studio equipment (and can't really afford Alien Bee's yet)

Most of my outside work is in the city / urban, parking is difficult. Being a former Marine I have no problem carrying equipment, However I also learned what you chose is more important than how much.

I'm Wes, from Pittsburgh. Semi Pro photographer for about 5 years. BA in Journalism. Associates in photojournalism. Any day I did not learn something new is a bad day. I have much more of your blog to read, so I imagine a few more good days ahead.

June 18, 2011 1:18 PM  
Blogger Bartosz Orłowski said...

Is there any sens to make some excercises with on-camera flash ?

December 26, 2012 6:32 PM  
Blogger David Hobby said...


Nope. We are here to get you past that. Using an on-camera flash as your main light makes your photos about as interesting as if you lit them with a flashlight taped to your camera. Which is to say, not very.

December 26, 2012 7:00 PM  
Blogger winclk said...

I don't quite understand metering the ambient light.

The settings I am trying to use are 1/125 and F2.8. When I use these settings I have to raise my ISo to 1600 or higher in order to zero out my meter. What am I doing wrong?


January 02, 2013 12:05 AM  
Blogger David Hobby said...


Open your shutter speed. Going to 1/60th would be an equivalent exposure at ISO 800. 1/30th would get you down to ISO 400.

FYI, in the future it is best not to ask tech Q's on a 6-year-old post comment thread. As in the Strobist FLickr Discussion Group, where there are over 100k people talking about this kind of stuff.

January 02, 2013 1:38 PM  
Blogger skewedlines said...

Thank you ever so much!

January 31, 2013 8:10 AM  
Blogger Bobs said...

This is the best explanation I have ever read about balancing flash with ambient light. Thank you!

February 12, 2013 10:20 AM  
Blogger vickylou81 said...

Say I want to control my DOF am I ok at increase the shutter speed rsther than stop down to get my underexposed image before adding flash? (as long as I dont go above sync speed)

Also can I do the same ting using Av and dial down the EV and then adjust flash EV to expose the photo as I would like? of i it best to have manual everything?

February 24, 2013 4:38 AM  
Blogger vickylou81 said...

Say I want to control my DOF am I ok at increase the shutter speed rsther than stop down to get my underexposed image before adding flash? (as long as I dont go above sync speed)

Also can I do the same ting using Av and dial down the EV and then adjust flash EV to expose the photo as I would like? of i it best to have manual everything?

February 24, 2013 4:39 AM  
Blogger sean lancaster said...

First, thank you for this terrific resource. I was on a page and saw you ask how often we hear this statement: "I am a purist, I only shoot available light."
You then conclude that this person is scared of flash photography. I don't consider myself a purist, but I only shoot available light because I enjoy the challenge of it. Flash photography can easily look artificial, so I don't want that look. Flash photography can also be done expertly and look great, which is why I am here to learn more. But I still think you could avoid making conclusions about available light shooters and still provide an excellent resource. Cheers!

July 22, 2014 4:57 PM  
Blogger Woon Cherk said...

Wow. Very insightful! Thanks for the detailed articles! :)

August 23, 2014 12:39 PM  
Blogger Betty S said...

Best explanation I read so far. Flash is finally starting to make sense to me. Thanks!!One question though: I have a cheap little back up flash (in case my flash fails) that doesn't have a stopping up or down option on the unit itself. Could I get similar results with flash compensation in camera?

September 03, 2014 2:14 PM  

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