Nikon Flash Use

1. Introduction

This note is written for beginners who want to learn how to make use of Nikon's Creative Lighting System (CLS) for flash photography. There are a lot of tutorials around that tell you how to use multiple flash units with sophisticated acessories such as reflectors and soft-boxes. But when I started to use Nikon's CLS, I found very little literature about the fundamentals of CLS, and how to pick the correct basic settings when using the system with a single Speedlight in the hotshoe for everyday, casual photography.

This, I hope, is a note that will make CLS more accessible. I think CLS is a great system. It is probably the most advanced dedicated flash system that exists. But with all that built-in cleverness, it sometimes seems like it has a mind of its own. So after a brief stint on terminolgy, I start off by introducing the built-in rules of the CLS. These rules are indeed helpful, but they can be perceived as limiting and frustrating if you don't know about them. So I'll tell you about them up-front.

To understand CLS, you also need to understand how your flash will behave in combination with the “ambient light”. This note will tell you that, and also the different settings on the camera and the flash you should pick under different ambient lighting conditions.

Terminology

Throughout this note, I try to stick to the terminology you'll find in Nikon manuals and literature. For a list of those terms, with a brief explanation, refer to my introduction to CLS.

Below is the definition of some of the other words used in this tutorial:

• Ambient light is continuous light such as natural light (sunlight), tungsten lamps or fluorescent lamps – as opposed to flash light.
• Flash light is a brief, intense burst of light made by a Nikon Speedlight or a similar flash unit.
• Flash key the when flash light is regarded as the dominant or sole light source.
• Fill flash is when the flash is regarded as auxiliary light source to the ambient light.
• X-sync speed is the maximum shutter speed a camera can use that exposes the entire sensor to the burst of flash. On Nikon DSLRs with a mechanical shutter, the x-sync speed is typically 1/200 second (e.g.: D5000, D80, D90), or 1/250 second (e.g.: D200, D300, D700, D3). On Nikon DSLRs with an electronic shutter (e.g. D70, D40), the x-sync speed is typically higher (1/500 second or more).

Environment

For the record: I own a Nikon D80 DSLR, the Nikon SB-600 and SB-800 Speedlights, as well as the Nikon version of the aftermarket Nissin Di866 flash. This is also the kit that has been used for testing the examples and scenarios described in this note. I hope that most of the text is general enough to be useful even if you have a different DSLR or use other dedicated flash units. However there may be omissions and inaccuracies, in particular with respect to equipment I don't own. Additions and corrections are welcome.

2. Built-in Rules

Nikon's DSLRs and dedicated Speedlights are pretty smart. One the things they come with is a set of built-in rules. Most of rules are put in place to prevent new users from shooting themselves in the foot. However, they may intrude upon your photography. Some may perceive them as design flaws or missing settings.

Below, I list three of the most annoying built-in rules that may intrude upon flash photography, and how you override them.

• The maximum shutter speed you can set with flash is the camera's x-sync speed. This rule is in place is to prevent the focal plane shutter from blocking the light from the flash. You may override this rule by setting Auto FP mode.
• In the exposure modes where camera controls the shutter speed (e.g.: Programmed Auto (P), Aperture (A), and green Auto), the camera underexposes the ambient. This rule is in place to prevent camera shake and movement from blurring the background . You may override this rule by setting slow-sync flash mode.
• The camera's built in flash pops up automatically and fires whenever you snap a photograph, even in places (like a football-arena) where the subject is very far away and the flash is useless. This rule is in place to make sure you use flash in dark light. However, it only happens when the camera is in one of the point & shoot exposure modes. To override this behaviour, select one of these exposure modes: Manual (M), Aperture priority (A), Shutter priority (S) or Programmed auto (P).

3. Matching the Ambient Light

You can benefit from the use of on-camera flash in all situations. Indoors, outdoors, in bright light, and in dark surroundings.

However, for best results, you need to apply settings to the camera and the flash that matches the ambient light of the scene you plan to photograph.

Below, we go through the process of picking some useful camera and flash settings under different ambient lighting conditions.

The process starts by determine the ambient lighting conditions of the scene. You can measure the light with a handheld incident light meter or with the camera's built in light-meter.

Below I describe no less three alternative formal methods to determine the type of ambient light. To be honest, I don't usually go through these rather cumbersome steps myself. Instead I just look at the scene and then make an educated guess about the type of ambient light. This is probably what you will end up doing as well. But I think it is nice to know about formal definitions and methods that can be used as reference when needed, so I describe these methods anyway.

Method 1: To measure the ambient light with a light meter, just set the meter to ISO 100 and the readout mode to show EV. Position yourself near the main subject and point the translucent plastic hemisphere of the meter in the direction of the camera. Meter, and read the measured EV directly from the light meter's readout.

Method 2: If you don't have a handheld light meter, you can instead use your camera's built-in light meter. Set the camera's metering method to centre weighted and use Programmed auto (P) mode. Frame the subject you want to meter in the viewfinder. Your camera won't have an EV readout mode, but it will let you know the aperture, shutter speed and ISO for correct exposure. When you know these three parameters, you can compute the EV number with the following formula:

EV = log₂(N²/S/(ISO/100))
(N = aperture (f-number), S = shutter speed)

Method 3: Set the camera's metering method to centre weighted and use camera to Aperture Priority (A) mode, set the sensor speed to ISO 200, and set the aperture to f/4.0. Frame the subject you want to meter in the viewfinder. Read the resulting shutter speed from the viewfinder display.

You should now be able to use the table below to determine the type of ambient light you have to deal with. If you used method 1 or 2 to meter the light, refer to the EV-number in the first column. If you used method 3, refer to the shutter speed listed in the second column. In both cases, you will find the type of ambient light in the third column. The last column is contains descriptions of some typical scenes where you will find this type of ambient light.

EV	Shutter	Ambient	Typical scenes
< EV 7	< 1/15	dark	interiors lit with tungsten, stage shows, fairs
EV 7 - 10	1/15 - 1/125	fair	interiors lit with fluorescent lights, ice shows
> EV 10	> 1/125	bright	subjects outdoors in the daytime

Below you will find suggestions for what settings you may use for camera and flash in each of the three lighting conditions.

Dark Ambient Light

When it is dark enough, adding light to the scene is probably the only way you can get a decent photograph. While dark ambient light is by no means the only lighting conditions when you should use flash, it is probably the condition where most people more or less automatically will turn on their Speedlights. Here is how to best use a single camera-mounted Speedlight when there is very little ambient light.

In dark ambient conditions, the camera's built-in exposure system will pick very slow shutter speeds to expose correctly for the ambient light if we let it. We don't want this. Instead, the power of the flash will be used to control exposure. This means that the flash will be key and essentially the only light on the subject. The ambient will contribute only to the background exposure.

In dark conditions, we don't care much about the ambient, so we rely on the TTL mode of the flash for exposure control. This is why we select the Manual exposure mode on the camera.

While I prefer TTL in dark conditions, some says that the non-TTL Auto mode (only available on some flash units) works even better for exposure control in this situation.

In dark conditions, the power of the flash will be used by Nikon's CLS system to control the exposure of your main subject. The ISO, aperture and shutter speed you choose does not impact upon the exposure of the main subject in dark ambient light (as long as your main subject is within the range of the flash). ISO, shutter speed, and aperture do have an effect upon other things, however.

The ISO setting determines the range of the flash. To extend the range of the flash, increase ISO. I want the flash to have some range in dark ambient light, so I usually set a medium high ISO speed. ISO 400 gives good flash range without being too noisy.

The aperture determine depth of field, background expsoure, and flash range. Open up the aperture to decrease depth of field, increase background exposure, and increase flash range. Stop down the aperture to increase depth of field, decrease background brightness, and reduce flash range. I usually find that f/4 wok wel in dark ambient light.

The shutter speed you select will only control the background exposure. Decrease the shutter speed to brighten the background, increase it to darken the background. You should be aware that decreasing the shutter speed increases the risk of motion blur impacting on the background. Also, you should not increase the shutter speed beyond the x-sync speed without turning on Auto FP mode. Note that if you do so and and set at shutter time faster than x-sync, the flash range will be significantly reduced. To not risk having motion blur in the background, I usually set the shutter speed equal to the x-sync speed (1/200 second on a D80) when using flash in dark ambient light.

Suggested initial settings:

Camera: Manual (M), f/4, 1/200 second
ISO: 400
Flash: TTL or Auto mode
Auto FP: Off
Slow sync.: Don't matter

(When the camera is in the Manual exposure mode, the Slow sync. flash setting don't matter because it is you, and not the camera, that set the shutter time.)

Bright Ambient Light

In bright light conditions the cameras built-in automatic exposure control will give a correct exposure for the ambient light. In this case, we only want the Speedlight to add fill flash to light up the shadows.

If you have a Nikon Speedlight, you should use TTL BL mode to allow CLS to automatically balance the subject with the ambient. If your flash don't have a TTL BL mode, the TTL mode will have to do.

The suggested setting relies on the Programmed auto mode, which let the camera pick the initial settings for aperture and shutter speed. However, you could also use Aperture Priority if you want to control depth of field, or Shutter Priority if you want to control motion blur. All these settings will expose for the ambient, and add fill flash to brighten the shadows.

The flash will be used to fill in the shadows with just enough light to balance them with the background. This only makes sense if your main subject is less bright than the back­ground. If your main subject already is brighter than the surroundings, there is no point in using fill flash.

Suggested settings:

Camera: Programmed auto (P)
ISO: 200
Flash: TTL BL mode (or TTL mode)
Auto FP: On
Slow sync.: Off

If you use the TTL BL mode, it will usually give you nicely balanced images with both the background and the subject correctly exposed. You might want to dial in a tiny amount of negative flash output level compensation (FOLC) to “subdue” the effect of the flash. I usually use -0.3 EV or -0.7 EV.

In TTL mode, the system will deterine the output level of he flash without taking the ambient into account. Since we are not using the flash as the dominant light, we need to set a negative FOLC that offsets the effect of the ambient. You may need to experiment to find the right amount, but I have found that -1.0 EV or -1.3 EV often works well.

Fair Ambient Light

In the two extreme lighting conditions you gives you a clear choice between either flash key (dark ambient light) or flash key (bright ambient light). The in-between situation, where there is some – but not very much – ambient light, is more complicated.

In this situation, we say that the ambient light is “fair”. This is when there is too much ambient light to make flash key the obvious choice, and there also may be too little light for flash fill.

The first thing to consider in fair ambient light, is what options we have. It may not even be possible to use flash key (where the flash is the dominant light), or to use fill flash (where the flash light is used as auxiliary light to supplement the ambient light) with good results.

Using Flash Key in Fair Ambient Light

If we are photographing a subject that is moving quickly (athletes, dancers, playing dogs), we may want to eliminate motion blur. In bright light, we can do this by picking a fast shutter speed. In dark and fair ambient light, using a fast shutter speed is not always possible. Instead, we can freeze motion by making flash the dominant light source. The duration of the flash burst is very short (usually only about 1/1000 second or less &ndash for actual durations, see the manual for your flash, or see the table on this page).

Another reason for using key flash in fair ambient light is to reduce the effect of mixed lighting.

To make the flash the dominant light, the light from the flash must be at least three stops stronger than the ambient light.

To use flash key in fair ambient light, turn off Auto FP. You should start out with the lowest ISO setting available on your DSLR (e.g. ISO 200) and shutter set to the shortest shutter speed that will synchronise with the flash (x-sync speed). In this example, we shall use 1/200 second, which is the x-sync speed for the D80. (If I had used a D300 I would instead have picked 1/250 second, and if I had used a D70 I would have picked an x-sync speed of 1/500 second.) The camera should be on manual (M) exposure mode, and the flash on TTL.

You start out by metering the ambient using a handheld light meter or the analog exposure display in the camera's viewfinder. Let us say that we ended up with the meter telling us that f/1.4 would be the right aperture to pick (i.e. ISO 200, f/1.4 and 1/200 second. This equals EV 7.6, which you should recognise as inside the zone of fair abient light: EV 7-10.)

Now, to underexpose the ambient by three stops, you close down the aperture by that amount. In the present example, this means you should use an f-stop equal to f/4 (f/1.4 → f/2 → f/2.8 → f/4). After you have adjusted the aperture, the analog exposure display should indicate a more than 2 EV underexposure. This should appear as something like the image below.

Suggested settings:

Camera: Manual (M), see text for aperture, shutter set to x-sync speed
ISO: lowest
Flash: TTL or Auto mode
Auto FP: Off
Slow sync.: Don't matter

Note that if the ambient light is too strong, we may not be able to overpower it. For example, let us say that correct exposure for the ambient is ISO 200, f/2.8, 1/200 second (EV 9.6). If we stop down -3 EV from f/2,8, we get f/8. However, at f/8, the reach of a camera mounted Speedlight is quite short. Unless the main subject is close to the flash, a single Speedlight may not have enough power to make flash key in this type of ambient light.

You should also know that it is not a good idea to use Auto FP mode to get fast shutter speeds if you want to make flash key in fair ambient light. This will mode will indeed let you use fast shutter speeds, but it will also reduce the guide number of the flash, making it too weak to overpower the ambient.

Other Options in Fair Ambient Light

If you find yourself in a situation where the ambient light is fair bordering on bright, setting up camera and flash for flash key may not be the best choice. The best option may then be to turn off the flash and just make use of the ambient light for photography.

Or, if the main subject is noticable darker than the surroundings, good results may depend on your ability to balance the flash with the ambient. In that case. follow the same procedure and use the same suggested inital setting as outlined above in the section describing how to use fill flash in bright ambient light.

4. Quick Summary

I shall end this segment by listing a quick summary of what you need to remember to use a single Speedlight on camera.

1. Determine the type of ambient light (dark, bright, or fair). You can do this with a handheld ambient light meter or your camera's built-in light meter, or you can train yourself to be able to determe this by making an educated guess.
2. Dark ambient is the type of light you will encounter most frequently indoors, at parties, during receptions, and when photographing family life inside your home, etc.) Use the camera's Manual (M) exposure mode together with TTL or Auto flash for best results.
3. Bright ambient is the type of light you will encounter outdoors during the day. This situation calls for balanced fill flash. Let the camera's metering system control the background exposure, and use TTL BL or TTL to control flash exposure.
4. Fair ambient light makes flash photography complicated. There is no “right” settings for this situation, and you need to weight your options carefully, including the option to not use flash.

5. Read More

The article you are reading is part of a series about dedicated flash for Nikon cameras. Here is an overview of the series:

• Introduction to Nikon's CLS – terminology and features.
• Overview of Nikon Speedlight models compatible with the CLS.
• Basic settings for different ambient lighting situations.
• More settings and modes, both on the camera and on the flash.
• Flash receipes for using a single on-camera Speedlight.

Copyright © 2010 Hannemyr Nye Medier AS | Theme: LimauOrange by Bob, used under CC BY-SA 3.0.