Tuesday, September 25, 2007

Lighting 102: 3.3 - Balancing Flash/Ambient Indoors

UPDATE: [ Completed exercises | Discussion ]

When last we met, we talked about moving from the idea of balancing a nice, even, back-curtain of sunset light to dealing with a highly directional light source (and learning to use it rather than just fill it.) This week, we are taking it indoors to apply the same principles to light that is less directional, less intense and more diffuse.

The common thread you should be starting to see is that there are two simultaneous exposures going on every time you use flash. This is true whether you make use of the second exposure or not. In fact, even if you are shooting with a disposable point-and-shoot and nuking your drunken frat brother with the flash at about, say, twelve beers into the party, you still have two exposures happening every time you push the button.

The difference between neanderthal and nuanced is learning how to finesse the ambient portion of your exposure. I mean, it's always there anyway, so why not use it?

In fact, the more you understand it, the more you realize that it is at least as useful as another flash. And sometimes even more so.

(More after the jump.)

Typical indoor ambient light, for instance, might be about 1/60th at 4/f at ISO 400. So If I shoot you in that light, available only, you are going to be properly exposed. You'll still probably look pretty bad -- we nailed the quantity, but the quality of the light is likely ugly as it comes from overhead fixtures.

So, I decide to stick an umbrella'd flash up near you and light you that way. After all, I think we have established that you need all of the lighting help you can get, right?

I put my camera at the max synch speed (1/250th) and put my flash on 1/4 power and light you up to f/8. As my umbrella is very close to you (yeesh - look at those wrinkles - I can fix that with soft light) we remember that the light is going to fall off very quickly and go pretty dark by the time it gets back to the wall, right?

So now you look great (all things considered) but the wall on the other side of the room is way too dark. The problem is, the only thing that is lighting the wall is my flash. That's because my ambient exposure is set to 1/250th at f/8, which is underexposing the non-flash-lit portion of the room by four stops.

So let's move from the hypothetical to the practical and do a little exercise in walking the ambient exposure up a little bit to see the effect of various shutter speed on the flash/ambient combo. Rather than use photos of you, dear reader, (we don't want to scare the small children, now do we) I'll use a camera as a stand-in.

In this room (my living room) the daytime ambient exposure is about 1/4th of a sec at f/4 at ISO 200 with the lights out. I have the blinds open so the back part of the room is receiving some light. The camera, in the foreground on a coffee table, is receiving much less.

The first thing I want to do is to establish that, at our starting exposure with no flash, the room would be black:

Here we are, at 1/250th at f/4 with no flash. This stunning exercise in minimalism is, in fact for sale. But only a true art lover would appreciate the beauty and meaning of a photograph like this, so please do not be offended if it appears overpriced.

At a 250th at f/4, the ambient light in the room is 5 stops underexposed. Darn near black, I'd say.

Next we'll add a little flash, in the form of an SB-26 in a shoot-through umbrella. Please forgive the umbrella ribs reflection in the front filter. I was working fast today. Besides, I had already made my artistic statement for the day and I was too bushed to be creative again.

But wait, what's that light on the back wall? Well, we already know that it isn't ambient, so it must be flash. Which is exactly what it is -- spill light from the umbrella.

So, let's open the shutter speed up two thirds of a stop to a 1/160th of a second.

Hmm. The background doesn't get any brighter.

Same thing for 1/100th and 1/60th. (Okay, maybe a tiny bit at 1/60th.)

This is simply because we are working so far from the ambient exposure of the room. If the flash is much more powerful than a given, combined ambient setting, I call that "working above the ambient," as in, "I was shooting flash at f/4, working 4 stops above the ambient."

That tells you that at f/4, my chosen shutter speed was four stops too high for the ambient exposure.

It's not until we get to 1/40th of a second that the ambient starts to creep in, albeit barely.

This is the threshold of the shutter settings at f/4 (and ISO 200) that will allow the ambient to burn into the flash's shadow areas in the photo. So here is where you'd start paying close attention to the TFT screen and adjusting your shutter to get the best effect.

At a shutter speed of 1/25th of a second, things are starting to happen.

Clearly the ambient is starting to make a more pronounced appearance here. Mind you, the camera is staying consistent because it is lit solely by the flash at this point.

The background isn't really usable at this point, exposure-wise. But the light is coming up and I am confident that I can fine-tune it to whatever tone I want.

At a 15th of a second, the background is getting usable.

From here on out (or up, actually) the tone of the background becomes a personal choice. There is no "wrong," as it is now a matter of how much separation I want between the subject and the background.

Remember when we told you to throw the concept of "proper exposure" out of the window? This is what I am talking about: The the exposure reference point is set by how you choose to expose the light falling on the camera. The background can be anywhere in a wide range of tones, with the choice being yours.

At a tenth of a second, my off-white wall is a rich tone, influenced as much by the color of the green-filtered shady light coming through the north-facing window as it is by the ambient portion of the exposure.

Doing an exercise like this (hint, hint) will show you just how much control you have over a situation once you start to understand the concept of balancing strobe and ambient.

At a 6th of a second, we are still below medium grey on the tonal level of the background. But now we are starting to get into a background range that, say, a newspaper might be able to reproduce.

The ultimate medium in which the photo is going to be reproduced will be your guide as to the limits of your chosen ambient fill level. But again, the choice within that range is yours.

One quarter of a sec.

This is my personal choice, as I like the "invisible" quality of the light and ambient combo for this picture. It's a subjective call, but for something like this the light can be made to disappear (not too obvious) and the photo just has a quality edge to it that does not look lit, but just looks nice.

At 0.4 secs (1/2.5) the room starts getting airy.

Remember, the walls are well above medium grey, so the camera considers this an overexposure of the ambient. Again, that "proper exposure" thing is a very fudgeable concept. You might like this frame better. There really is no right or wrong here.

At 0.6 secs, the background looks airier still.

I could go up more on he ambient, but the highlights in the center right portion of the background would start to blow out, which would be distracting (but still not "wrong," IMO.) There is more leeway here than in a Composition 101 paper in 9th grade.

The first concept that you have to learn is that there is a base exposure that will render any scene as black. Indoors, this is frequently an easy exposure to achieve while still being at or below your synch speed. From there, merely opening up the shutter will allow progressively more ambient light into your photo until you get exactly the balance that you want.

Here's something else to think about: Your tripod is another flash unit, but with near-infinite power. Say you are shooting in a huge, cavernous, dimly lit, windowless room. You could umbrella-light someone with a flash in the foreground, and just hold that shutter open until the room was raised exactly to the supporting exposure that you wished. Just lock your camera down on a tripod and leave the shutter open until the whole, "unlit" portion of the room burns in.

I have done it (on a tripod) for 30 seconds at f/2.8. The person swayed just a tad during the exposure. But honestly, that made it look even better. And speaking of movement, one last shot:

Given a quarter second of shutter with which to play, of course I am gonna try a little flash-blur.

But that's not until Part 7, so let's save that for later.


____________________________________

We still haven't finished the balance unit. So this week's exercise is just that, rather than an assignment.

I did these demo shots in ten minutes, literally, from light setup to final frame. It's really no big deal to try something like this in your living room.

The important thing to remember (as it always is when "burning in" ambient against flash) is to have your flash-lit subject in a part of the scene that is receiving less ambient light than the ambient-lit part of the scene. In practice, this usually means shooting into a brighter background and lighting your subject with flash in the foreground.

Remember, the whole distance thing still applies. So keep that flash in close, lest it contaminate your background.

FYI, here is a shot which shows the incredibly difficult and complex setup that was used to make this series of shots.

(That's "Ginger" sniffing the umbrella, by the way. She's not the brightest bulb in a three-pack, but she's very sweet.)

One final note on the umbrella: I "choked up" on the shaft a little but, which means that I did not make full use of the full umbrella as a light source. Reason is (other than that I did not need the full light source at this small distance for the light to be soft) is that I did not want any raw light to spill past the edges of my umbrella and further light the background.

If you are doing the exercises, please tag your photo(s) thusly:

Strobist
Lighting102
exercise
balance
indoors

You can view the completed exercises of others, here. There is a discussion thread set up for this post here.

Finally, given the range of background tones that would have been displayed on the back of your camera, which shutter speed would you have chosen, and why?

Hit us in the comments.


NEXT: Assignment: Balance


__________

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39 Comments:

Blogger Thomas said...

where's the ambient only shot for comparison?

September 25, 2007 8:56 PM  
Blogger David said...

Thomas-

You may be missing the point of the exercise:

The flash exposure is the constant, and the ambient exposure is highly variable -- and wherever you want it to be.

Which ambient exposure would you like? There are at least half a dozen up there -- contained within the flashed photos.

September 25, 2007 9:05 PM  
Blogger Thomas said...

This comment has been removed by the author.

September 25, 2007 9:11 PM  
Blogger Matt Greer said...

I'd also like to see the ambient-only shot of the 0.4s, f/4 shot, just to see what the flash exposure is adding to the image. I see some highlights on the camera that the flash adds, but what is do to actual exposure in that frame?

September 25, 2007 10:14 PM  
Anonymous Anonymous said...

Hi. I enjoy your posts a lot. Thanks for your generosity.

Something to bear in mind though, your use of the term shutter 'speed' can be confusing to the beginner (me). This is because it's not a speed at all, it's a *duration*. When you say 'below xxx shutter speed', do you mean below that duration, ie 1/500 is below 1/250? Or do you mean below that speed, ie 1/125 is below the speed of 1/250, since it is not as fast (ie its speed is below). You see what I mean: the word below is confusing when referring to exposure durations as a speed.

Hope this feedback is useful.

September 25, 2007 10:17 PM  
Blogger Karl said...

I would use 1/10 because there is richer color in the background and it is more dramatic. Light and airy is boring.

Ummmm, If you want to see ambient only, you might want to put your camera on a tripod at ISO 200 in a room with one window not getting direct sunlight, and try seeing what happens with different shutter speeds and no flash. Ambient only at 1/250 is very minimalist.

September 25, 2007 10:51 PM  
Anonymous Pamela Vasquez said...

I am finding that when I print these out the pictures are not printing where they are in the article. They are all printing on top of each other at the end. Is it only me? This never used to happen.

Thanks. pam

September 25, 2007 11:00 PM  
Anonymous Anonymous said...

Hi...

I have a quick question. As you increase the shutter speed, you dont adjust the flash power on the foreground object. Is this because the background is lit by the ambient, and the foreground is (relatively) not?

I would think that for an evently lit room, increasing the ambient would mean overexposure on a flashed object, and a required decrease in flash power - correct?

Thanks!
-Andrew

September 26, 2007 12:00 AM  
Anonymous bbphotova said...

Andrew,

There's no need to adjust for the flash as you already set the proper exposure for it in the beginning. The flash is only about 1/1000th of a second (or less) in duration, so its exposure never changes, no matter how long you leave the shutter open.

The ambient, however, will change according to the shutter speed you use.

That's what David means by technically having two exposures going on at the same time in the picture.

Does that help?

September 26, 2007 1:07 AM  
Anonymous Justin said...

To the anonymous folks asking questions, you might find that David has already answered what you are asking in previous posts or assumes you have a certain amount of general photography knowledge (being a beginner to off camera flash is one thing, but not understanding the term "shutter speed" is neither here nor there). Read up on the previous articles or try asking in the Flickr discussions forums instead.

Anyway, great post as usual David.

September 26, 2007 1:07 AM  
Anonymous Tobias said...

I like the 0.4 sec best. Gives the wall a nice creamy tone. I also like the highlight created on the back wall. I guess it is light coming from the window.

Nice post David, now I just want to sneak home from work and start the excercise.

September 26, 2007 3:08 AM  
Blogger Mikko said...

Typo, add missing verb:

"This is my personal choice, as I ________ "invisible" quality of the light and ambient combo for this picture."

September 26, 2007 4:06 AM  
Blogger Kyle said...

To Andrew-

In a truly evenly lit setting, you would be correct, but the key thing to note here is (as David puts it in the post) that you would want your subject in a lesser ambient-lit location than your background, so that your background has a higher exposure than your subject.

Shooting a dark subject against a brighter background offers you more control of the background exposure via the shutter speed because any adjustment in shutter affects portions of the frame directly relative to the amount of ambient falling on them. If David were to include a setup shot without firing his SB-26, you might notice that the camera on the table receives less ambient light than the wall, because of the umbrella cutting the light from the window at right.

It's all about the ratios.

Hopefully a different spin helps.

Kyle

September 26, 2007 4:16 AM  
Blogger Mariano said...

Pamela, it doesn't work for me in Firefox, but Safari prints it out alright.

That's the beauty of HTML/CSS, always full of surprises, any day, any browser any platform ;-)

September 26, 2007 4:23 AM  
Anonymous Mat said...

One question if I may.. something that's always been bothering me and I still don't know the correct answer.
I do understand this light balancing and I love it. But the thing is, let's say I want to photograph a person in a room. I setup an umbrella close to the person and set it to f8 at 1/500 (I use D70s). The person is correctly exposed, room is black. So I drop the shutter to 1/10 to get some light in the room. So my question is (finally) if I shoot at 1/10, will the person in front be sharp or blurred? Rule of thumb is 1/60 for hand shots, so what happens here?
I hope you know what I mean and could give me an answer.

TIA!!!
Mat

September 26, 2007 4:44 AM  
Blogger pjbarford said...

Flash only lights in a quick burst, so the shutter speed is irrelevant to the effect the flash has on the image (unless you have a shutter synch that can go really really high). The shutter is only relevant in how much ambient light (i.e. constant light) is hitting the sensor. This is I think is what David has been trying to get into our heads over the last few 102's.

My look on this is flash and aperature are linked, the more open the aperture the less power on your flash you will need and vice versa. Then you use the shutter to control the ambient light in the scene.

September 26, 2007 4:48 AM  
Blogger pjbarford said...

Flash only lights in a quick burst, so the shutter speed is irrelevant to the effect the flash has on the image (unless you have a shutter synch that can go really really high). The shutter is only relevant in how much ambient light (i.e. constant light) is hitting the sensor. This is I think is what David has been trying to get into our heads over the last few 102's.

My look on this is flash and aperature are linked, the more open the aperture the less power on your flash you will need and vice versa. Then you use the shutter to control the ambient light in the scene.

September 26, 2007 4:49 AM  
Blogger Grega said...

Please forgive the umbrella ribs reflection in the front filter.

OK, it seems that I am the only one that has trouble finding the way to remove those ribs. How on earth?

Thanks.

September 26, 2007 5:50 AM  
Blogger Boris said...

In this example, i would choose the 1/10th or maybe the 1/6th version.

Why? Because i like it more if the black camera "seems" to be lighter than the (ambient) background. With slower shutter speeds the ambient burns in more - to much IMHO - so that my eyes will look around to explore the background instead of the subject: the Cam!

September 26, 2007 6:10 AM  
Blogger David Ziser said...

Hi David,
Great info. You may want to share with your readers what we are doing over at www.digitalprotalk.com. I am in the middle of my Digital Master Class this week and we have been shooting on location for the past two days. Today, I posted several images that speak to exactly want you are covering in your Lighting 102 posts - balancing the light with the ambient - inside and out. In fact you may want to check out some earlier posts as well in which we cover the wedding side of what you discuss. I've been visiting your site almost since it's inception. Continued success to you and all the best. --David Z.

September 26, 2007 8:00 AM  
Blogger Joe Holmes said...

I think one of the keys to understanding all this Two Exposures stuff is that the flash takes up only a tiny portion of the time the shutter is open. The shutter remains open for a relative eternity, properly exposing the ambient background according to your taste, while the flash does its nanosecond pop to take care of the foreground somewhere during the open shutter. It took me a while to take all of that in.

You the photographer control each of those two exposures, by first setting the foreground/subject/flash and then by discovering the appropriate shutter speed to catch the ambient light.

(You could also use shutter priority and search for the appropriate aperture for the ambient light, but that's kind of silly since you'd be giving up control of depth of field.)

I do it in a different order than presented by David -- I set my aperture for my ideal DOF for the situation, see what the camera sets for "perfect" shutter speed, set the camera for that aperture and shutter speed in Manual mode, then make adjustments for taste. When I'm happy, I start to test for the best flash setting -- often, using TTL does a great job, but otherwise, manually.

It's all a bit hard to grasp because nearly all of us are familiar with setting shutter and aperture for ambient light, but the workings of a zillionth of a second flash are mysterious and difficult to visualize.

September 26, 2007 11:00 AM  
Anonymous Anonymous said...

Hi David:

Thanks, as always, for a great explanation. I have tow questions.

First question: while your example works great for something not moving, will you be covering anything in regard to working with moving subjects? I am thinking about, for example, my 3 kids who are all under the age of 4. Getting them to sit still for a 1/4 sec shot would be next to impossible.

Second question: how do I post samples to the Flickr site for critique? I am a flickr user (Keith E), but not sure how to post to your site. I have only recently begun reading your site and trying stuff. I'm new to the world of blogging and forums, so would like to get more involved now that I know you're here.

Thanks so much!

Keith Eng

September 26, 2007 11:09 AM  
Anonymous Anonymous said...

Hi all, and thanks for another great post David!

The last photo is very revealing for those of you concerned about moving subjects and flash durations. As David says, there are two exposures going on here!

In this photo, David uses a 1/4 second exposure and dials the camera zoom during the exposure which blurs the background. But note that the camera alone is completely in focus!

How? The flash is lighting the camera only (not the background) and the flash fires so quickly that it effectively freezes the zoom which is moving slowly compared to the flash duration. The exposure for the background (1/4 second) is long compared to the "zoom time" and thus that part of the exposure is blurred.

Subjects illuminated by the flash will be frozen in time in a long exposure. This is a crystal clear example of that, thanks David!

September 26, 2007 12:45 PM  
Blogger Tri said...

Hi Keith, to answer your second question. To join the flickr, click on groups, search for strobist, and click join groups. You're all set!

Thanks David for another great learning experience! I truly appreciate every bit of knowledge you have to share with us.

Thanks again,
-Tri

September 26, 2007 5:11 PM  
Anonymous Daniel said...

Thanks for another GREAT lesson, David!

You make "learning" fun and simple.

September 26, 2007 6:27 PM  
Anonymous Pamela Vasquez said...

Thanks Mariano...I have Firefox....never heard of Safari...thanks for responding though :) Pam

September 26, 2007 10:47 PM  
Anonymous Anonymous said...

David, just a recommendation: on longer posts, could you include the Flickr submission links early in the article so that we don't have to click and view the whole article, then scroll down to the link in order to see the latest submissions. After reading the article when it comes out, I like to come back every few days and see everyone's photos but I don't need to see the whole article again. Thanks.

September 27, 2007 11:29 AM  
Blogger Jan Klier said...

I've just tried out my new exposure meter (Sekonic 758DR) and it has a function which is quite valuable for this exercise:

The meter can test fire the flash via a PocketWizard and then analyzes both the ambient and flash components of the exposure, displaying the percentage of light from flash, as well as f-stop equiv for the ambient and flash components.

More details with some example shots at exposures with flash meter.

October 01, 2007 11:24 PM  
Anonymous Anonymous said...

I cheated. I'm still in lighting 101 but jumped to this exercise following some idle thread while reading new posts. But what an eye opener it is for a rookie strobist! Thanks again David!

November 07, 2007 12:40 AM  
Anonymous Tony said...

Hi David,

Thank you very much for all of the work that you have done on this site to present the lighting concepts you have. I have learned a lot from what I've read. I am wondering if there is an index of Lighting 102 posts somewhere so a person can follow them from one to the next. I didn't even know there was a lighting 102 section until I read it somewhere else and came here and searched for it. I had already gone through the 101 course and didn't know there was another. I've gone through 102 until, I think, section 2.1 or 2.2 and then there wasn't a link to the next section. I tried searching for other sections and found 3.2 and 3.3 but none of these sections have links to the next one in line. I also don't know if there is any more 2.? sections left. An index of some kind, maybe with a link to it in the top-right corner of the pages would help to be able to follow the course. If there is already something like this, I apologise for the post, but I haven't been able to find it.

The way these sections build on each other I hate to try and continue without being able to see each in turn.

Thank you again,
Tony

December 22, 2007 12:43 AM  
Blogger C said...

How one approaches same topic with a live subject(peson) that can't sit still for more than 1/2 seconds ?

Even if you try rear curtain the subject movements will make the movement show.

December 26, 2007 5:03 PM  
Blogger Logan said...

I know this example is about balancing exposure, but does anyone have tips for balancing color temperature in situation, like this one, where flash & ambient light are used. I've been in the habit of shooting RAW and tweaking the white balance in Photoshop. Any tips?

January 10, 2008 4:38 PM  
Anonymous Anonymous said...

Greetings all. I hope this is the right place to ask this question rather than in the Flickr Group but as it relates directly to this post, here goes. I understand the techniques being described here but want to know the thinking behind going from an ambient exposure to a flash exposure. In this post, David starts by saying

Typical indoor ambient light, for instance, might be about 1/60th at 4/f at ISO 400.

But then he says

I put my camera at the max synch speed (1/250th) and put my flash on 1/4 power and light you up to f/8.

What is the thinking involved in going from an ambient exposure to a suitable flash exposure. I can see that setting the shutter speed to the max synch speed is a good starting point from which you can gradually build up the ambient, but what is the reason for reducing the aperture to f8 (I presume 'light you up to f8' simply means setting f8 on the camera??) and setting the flash power to 1/4 - Is this just experience in this sort of situation or is this a good starting point for all flash shots??

Regards
John

January 14, 2008 12:22 PM  
Blogger rachel mae said...

Thanks for the online lessons sir!

February 17, 2008 5:56 AM  
OpenID Avangelist said...

Well this is quite interesting, but doesn't quite make sense to me, perhaps because of the setting, I am not sure.

That room is clearly well lit with daylight right? so what is the flash doing in the first place? Is it just adding fill on the front of the camera? I don't quite get it. Plus going all the way down to 1/10 is no good for hand hold only tripod as somebody else mentioned above.

Sorry for dragging out a 2yr old post.

I am not saying what has been done is wrong or anything like that, just that I have always understood for fill to meter ambient first then dial the flash until you get a balance not change the speed?

February 23, 2009 4:18 AM  
Anonymous Anonymous said...

Thank you so much for posting this, a million lightbulbs are going off in my head right now, and it's thanks to this blog.

July 10, 2009 4:37 PM  
Blogger Oli said...

I only recently discovered the "strobist", but already learned a lot about lighting. Big thanks for sharing all the information!

During the ambient light exercise I came across a challenge that I finally solved - I guess only due to the understanding of light I gained reading 102 and related posts...

What happened? I had my object (a book) properly exposed with flash and started to increase shutter times. When the background started to creep in I recognized that the ambient light was also affecting the look of the book... My first thought was "I need more flash power" which of course didn't help. After remembering that I have full control of the light, I simply "goboed" the ambient light by placing a cardboard between the ambient light source and the book, so it was completely in shade.
Probably this was one of those "click" moments

November 01, 2010 6:55 PM  
Blogger Pamela Oliver Munoz said...

I feel like Helen Keller when she discovered the connection between the water at the well and the words Anne was spelling into her hands.

Thank you is not enough.

January 21, 2012 5:02 PM  
Blogger Allie Stevens Catchings said...

^^ what she said

January 29, 2012 8:58 PM  

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