John Fjeldsted Photography - Creating Natural Radiance

Creating Natural Radiance

Not every picture we wish to create provides ideal lighting. In this case, we need to bring additional light to the scene. A common approach is to edit the images to give the appearance of Natural Radiance. While much can be achieved in post through editing, there are often situations where there is no substitution for providing additional illumination when the picture is taken. This section presents three techniques and gives a few examples. The next section introduces the topic of how to edit images to increase Natural Radiance when lighting is less than ideal. In practice, I often find myself adding light through the use of on- or off-camera flash when taking the picture which improves the overall result and reduces the the amount of editing required.

Using a Reflector

Often perceived as the easiest solutions to adding light to our subjects is to use a reflector. Reflectors are commonly round and come in various sizes (diameters) and reflector materials. They are easily collapsed to a smaller size making them relatively easy to bring along. My favorite reflector is a Photoflex 32" LiteDisc which has a zig-zag gold/silver front side and a white back side and collapses to a 12" diameter. The white side works best for reflecting light from the sun to lighten shadows and keeps the light diffuse. The more reflective gold/silver side works well to reflect light from open sky, but produces harsh lighting if used to bounce direct sunlight.

A common question has to do with reflector size. It's generally suggested that the illuminated area is roughly the same as the disk diameter. It is possible to enlarge this slightly by bowing the reflector to spread the light, but this can be a little hit and miss. To my thinking, 32" diameter can nicely illuminate the faces of one or two people under most conditions. If you have more individuals in the picture or need to light up a larger area, then you would either need a larger disk, which I find inconvenient, and often still does not provide wide enough illumination for a larger group.

A reflector has its greatest benefit when there is already a good light source available, and you wish to reflect it into the scene. Here are two good examples:

When doing close in shots, place a reflector below the subject's face or to the side to act as a fill light.
Holding the reflector up high and use it to act as in the place of a key light.

While it is possible to use a clamping arm and stand to hold a reflector, in most cases, using a reflector requires an assistant, or the subject holding the reflector in his/her lap to get the desired lighting effect.

The positive arguments for using a reflector include being able to see its effects directly and optimize accordingly. Also, there is no need to be work with various camera flash modes. The downside is that the illumination is constant and can be relatively bright which can effect the subjects expressions. With a reflector, actual control of the amount and directionality of the light you wish to add is generally not as easily controlled as it is when using an electronic flash. It also commonly requires an assistant. As a result, I rarely use reflectors.

Before you read about the use of On-Camera and Off-Camera Flash, you may wish to learn about Flash Basics below.

On-Camera Flash

The simplest approach to adding additional light to your subjects is to directly mount an electronic flash to the camera hot-shoe. This provides both a mechanical mount plus the needed electrical connections.

On-camera flash affords you two approaches to lighting your subject. The first is direct illumination. The second is by directing the flash away from your subject and bouncing the light on to them. In most cases, bounce illumination is preferred. This is because bouncing light off a ceiling or wall creates diffuse natural lighting. Of course, if you are outside or inside with very high ceilings or without a close wall, or if the walls and ceilings all have an off color that would cause an unwanted color cast, then direct illumination may be the only option. Under ideal conditions, bounce lighting can also achieve the effect of having your main light source being off-axis from your camera, resulting in improved modeling of the subject.

Leica SL2-S, Noctilux-M 50mm/0.95 @ f/2.8, 1/160 sec, IS0 200, B+W ND1.2 Filter, SF-58 Flash

When using direct illumination (and optionally with bounce illumination), it is generally preferred to use some type of diffuser to soften and broaden the light source. There are numerous after-market options, some better than others, but some diffuser should be used in any case.

Using on-camera flash together with TTL mode (see description below) allows you to shoot quickly in dynamic situations. This is ideal for wedding, family, and event photography as well as other fast moving situations.

If I am shooting under low-light conditions then I generally set the exposure levels without compensation to either the ambient exposure or the flash level.

If I am shooting with flash outdoors a a fill flash, then I will often set the ambient exposure compensation to minus 1/2 stop and the TTL flash level to minus 1 stop. Reducing the ambient exposure compensation helps reduce the chance of over-exposure with flash being added to the scene and setting the TTL flash level to minus 1 stop provides a fill, reducing shadows and improving (warming) the color of the light.

When shooting with on-camera flash I use a Leica SF-58 flash in TTL mode and when possible bounced. For Flash Fill work, I begin by set the camera Exposure Compensation to minus 1/2 stop and the TTL flash level to minus 1 stop and make adjustments when needed.

Off-Camera Flash

Off-camera flash allows you the maximum amount of creative control. Your approach can range from a single on-camera flash that you move off-camera to multi-flash lighting using a wide range of modifiers, including umbrella or softboxes.

The first step to moving a flash off-camera is to place a transmitter in the camera flash hot-shoe. There are two options. One is to use a flash which also includes the transmitter function to remotely connect to additional flash units. The other option is to use a mount a dedicated transmitter.

There is truly no limit to the lighting configurations that you can consider. Having numerous possibilities may be biggest reason many photographers don't take advantage of off-camera flash. To overcome this hurdle, begin with just one off camera light. The picture of Francesca and Kaleb is one such example. In this case, the picture was taken at dusk after the temple lights had come on. There was still enough light to capture color in the trees, lawn and mountains in the background, but not nearly enough ambient light for the bride and groom. Here are the details.

Francesca and Kaleb - Leica SL2-S, Noctilux-M 50mm/0.95 @ f/0.95, 1/60 sec, ISO 200, 20" Softbox off-camera Flash

First, it's important to have a setup that I can shoot alone without an assistant. I need a kit that I can setup quickly, then move from location to location and still have great light. The Angler 20" Octagonal Fastbox (also available in 24" and 28") is a baffled softbox that sets up with a single flip and click. It has an integrated twist-lock stand adapter which allows you to also set the angle. It uses a quick release adapter that accepts various flashes, both on-camera types as well as off-camera models such as Godox AD100 and AD200*. As the combined flash and softbox are quite light, it is easily be supported with a 6 1/2' lightweight stand. Complete setup is possible in about 60 seconds.

Mounted on my Leica SL2-S is a Godox XPro IIL Trigger (transmitter) which remotes to the AD200Pro (or other Godox flash). The Godox transmitter is easy to use and adjusting the flash level is instant. I generally work in Manual mode, though TTL works very well and can be used as a first test shot and then switched to manual mode which remembers and shows the TTL power level used.

In Summary

Achieving Natural Radiance requires great light. There are many photographers that limit themselves to working only with availble light, and sometime refer to themselves as natural light photographers. While I wholly advocate finding and using the best natural light that is available, the proper use of flash lighting can augment available lighting, making a good shot great, and open up possibilites that otherwise would be completely out of reach.

*I've made a simple modification by removing the tightening knob for the AD200Pro bare bulb head so that I can use it in the standard Angler Fastbox adapter meant for on-camera flash. In addition, by extending the bare bulb 1 inch further into the softbox using home made extension pins I get better illumination uniformity and increase the total light output, achieving a guide number of 28 (in meters).

Information: Flash Basics

First, it's important to understanding how a flash works. As the name implies, an electronic flash delivers a very short burst of light. To achieve this, the electronics in the flash internally generate high voltage which charges a capacitor. The flash occurs with stored electric charge is directed to the flash tube. The amount of light the flash delivers is directly proportional to the length of time (duration) that the electric charge is delivered to the flash tube. At very low flash levels, this period may be as short as 1/30,000 of a second. At the maximum power level the flash duration can reach up to 1/100 of a second.

As long as the flash duration is shorter than the shutter speed, then changing the shutter speed does not change the exposure which is contributed to by the flash. Of course, changing the shutter speed, does change the amount of ambient light exposed in the image. Beside changing the actual amount of light delivered by the flash, we can change the relative contribution between ambient and flash exposure by changing the shutter speed.

Each camera has a maximum shutter speed that can directly be used with a flash, called the flash sync speed and is typically between 1/125 and 1/250 second. The maximum shutter sync speed corresponds to the speed when the shutter curtain allows for full illumination of the camera sensor. When the shutter speed is shorter than this time the gap in the shutter curtain is reduced to less than the full width of the sensor. Taking a picture with a shutter speed less than the sync speed results in only a fraction of the sensor being exposed.

There are several modes which can be used to set the amount of light the flash delivers. This include Auto, TTL and Manual as well as support for High Speed Sync. As each camera vendor has their own electronics control systems, the flash you use needs to be compatible. This is particularly true for TTL mode and for HSS support, where as Auto and Manual mode can offer some general interoperability.

Auto (historically as referred to as Auto-Thyristor) uses a photo sensor on the front of the flash to measure the amount of light that is reflected back to the camera and flash. One selects the desired f-stop at a given ISO setting and when this exposure level is reached, as determined by the photo sensor, the flash pulse is completed.
TTL (Through The Lens metering). In this case, the exposure control is accomplished within the camera. The camera, generally causes the flash to make a short pre-flash, and the amount of light coming back from the subject is evaluated as part of the overall exposure and used for the actual picture flash which follows within a small fraction of a second. Integrating the exposure control into the camera allows for the use of both exposure compensation based on the ambient light and the relative amount of light from the flash.
Manual control allows the photographer to directly set the amount of light the flash delivers. This is generally set as a fraction of the flash or strobes' full power. Manual control is preferred when we look to remove variation in flash exposure. This is particularly true in shooting a subject that is backlight and the ambient exposure varies significantly based on how much of the illuminated background is brought into the auto exposure setting. As the flash level is then derived from this reading, the exposure variation results in significant changes in flash brightness. To make the use of Manual mode more straightforward, at least one flash manufacture (Godox) allows you to take a test picture in TTL mode, then switch to the flash to manual which directly remembers and displays the manual power level used with the TTL test picture. One can then dial the flash exposure up or down to achieve the desired and consistent results.

Working beyond the camera sync speed limit - There are two common uses for flash. Most people are familiar with is the use of flash when lighting is dark. The second, less familiar case is to provide illumination to subjects when they are in the shade - where the light is less than ideal - meaning, the light falling on our subjects is significantly reduced below the background lighting levels and/or has a color cast that may be cold (illuminated by open blue sky) or color shifted as if filters through overheld foliage or reflected of green lawns, etc. Using a flash daylight situations is commonly referred to as Fill Flash.

When using flash in dark settings, the ambient light level is low, and there is generally no problem in using a shutter speed less than the sync speed limit of 1/125 or 1/250 second. When the we want to use the flash as Fill Flash, and in particularly shooting wide open at a low f-stop, one can expect the shutter speed will significantly exceed the sync speed limit. There are two options. One option is to add a neutral density filter to the front of the lens. This reduces the overall amount of light - directly compensating for using a wide open aperture. The other option is to use a flash and camera that support high speed sync.

HSS is able to support the use of shutter speed beyond the native sync limit by operating the flash in a "pseudo" constant illumination mode. It achieves this sustained illumination mode through very fast pulsing of the flash tube that continues during the full movement of the narrowed curtain width across the sensor. This mode is not achieved without a price as the absolute brightness of the flash is reduced (effectively reducing the flash guide number) - and because it now acts as a constant light source, additional increase in the shutter speed reduces the effective lighting even further.
Neutral Density Filters, like other lens filters, come is sizes that match the diameter of the thread mount on the front of the lens. Beside, this diameter, they are also specified by the reduction in light they provide. This is either specified in the number of f-stops (each f-stop is a factor of 2) or the logarithm of the light reduced. An example is an ND 0.3 filter reduces light by 2 (or 1 stop). An ND 1.2 filter reduces light by 16 (or 4 stops) - which would allow you to open the f-stop setting on your lens from f/5.6 to f/1.4 while keeping the shutter speed constant.

Because of the reduction in overall reduction in flash power and the relative shift in flash power when increasing shutter speed in HSS mode, I very much prefer to use ND filters for Flash Fill shooting. The use of ND filters is fully compatible with TTL and Manual modes. If you wish to use ND filers for Auto mode, simply add the number of stop the ND filter attenuates the flash to the aperture set on the lens when setting the power level on the flash.

Continue reading: Editing for Natural Radiance

Table of Contents: Fundamentals & Techniques

Note: Indicated f-stop are nominally correct, but as with all M lenses, the camera estimates the value from the exposure and does not provide a direct lens reading.

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