EFP – So, What’s Up With Light?

Hey Buddy, You Need A Light?

Light’s Characteristics

Specularity/Diffusion

Stars in the nighttime sky are point sources of light. A north facing window produces a soft light that is very diffuse. Depending on what result you wish to have, select a light source that is specular, diffuse, or somewhere in between. A typical electronic flash is more specular and needs reflectors and/or modifiers to be diffuse.

Direction

From Digital Photography School

Studio photographers play with light placement to produce different and interesting results. There are lots of good Internet tutorials on this. Check out some of the cheat sheets, too. You need certain types of equipment to experiment. (Or, just you use lightbulb on an extention cord to observe what happens as you change light direction.)

Intensity/Size

Intensity and size are related. Both characteristic are also related to specularity and diffusion. Studio lights tend to be both more intense and larger. Electronic flash, not so much…so you need to adjust techniques and expectations.

Color Temperature

This is related to color balance in the sense that a photo sensitive medium (film, digital chip) can be matched to the mix of colors in what appears as a white light. Although it looks normal to the eye, some mixes are warm (more red) and others cool (more blue). Some light sources are green (ugh).

What About Mixed Light?

mixedlightcolortempexample1

Mixed Color Temps

In the photo example here, we have mixed light. There’s flash (foreground on the magazines) and is cooler (close to daylight). The wall and people are lit with overhead fluorescents and tungsten spotlights These are warm (like they’re lit from a fireplace). It’s a mix that’s hard to shoot and, if necessary, fix in post. You can’t pick one sensor type (film or digital) to cover all of them, so you photograph based on the predominant light and hope for the best.

With a single source, because sources (incandescent lights, electronic flash) have known mixes, you can easily match your sensor type. Change film or set your digital camera’s white balance accordingly. Other sources (cheap LED’s, sodium-vapor lights, CFL’s) can be much worse because their mixes (proportions of red, green, and blue that make up white light) can be hard to match.

CRI (color rendering index) is a numeric way of reporting the quality of colors in a white light source. The higher the number, the better. (Look for CRI’s over 95.)

Reflections & Reflectors

Light reflects and you need to be aware of reflection in your photographs. Light also can be reflected to good purpose. So, bouncing a light source (relecting it) can change its characteristics, which can also affect reflections. (Especially in the eyes.)

Cost

Light isn’t cheap. It can be heavy. If you have a complicated setup, better have help and your help should be able to anticipate your needs and understand your instructions. You have to carry it in, set it up, check settings, fine-tune to make people look awesome, make the shot, and then break it down and cart it away.

Resources

People

With reflectors, additional light sources, stands, and safety items (sandbags?), you probably need help to get the shot. Practice, practice, practice!

Safety

If it’s just you and a camera, then maybe it’s easy. If you have cables and light stands and booms and reflectors and gobos/flags and diffusers set up, it’s a recipe for an accident. Think safety.

Stuff

Some things that are very useful on site is inexpensive (gaffer tape, clamps, clips, white cards, grey cards…an all the bags to cary them.

Dollars

A high-end flash can be hundreds of dollars. If you want more than one, then even more. If you use studio flash, the numbers vary. The rule that “you get what you pay for” is appropriate.

On the other hand, go into a Home Depot and get cheap reflectors and incandescent bulbs (or CFL’s) and you can save a lot. But, this is about electronic flash. Right? Can you mix light sources? Sure…just watch out for color temperature.

Time

Always budget more time than you need. Do this for when your goofing around (practicing) and especially on site in the middle of a shoot (for when things go wrong and you have to fix them).

If you are working with a client (subject), be assured…they will get bored if you are doing a lot of fiddling. (This is why practice makes sense with friends who are also photographers as they won’t get bored.)

Exposure

If you are familiar with the Sunny 16 Rule, you know that you can get by, in a pinch, setting your camera based on just knowing what will work. With flash, this could be true, too. If you know what your unit can do at certain distance under a certain set of conditions, then you set your camera’s shutter and lens’s F-stop and shoot.

But…what happens when things are not following the default set of rules. You have to adapt.

Flash Meter

In a studio setting, this is a tool you almost have to have. If you are setting up for a certain configuration of lights (specular/diffuse, size, distance, intensity, sensor sensitivity), having a flash meter is invaluable. You can’t rely on modeling lights and regular meters.

You could use a digital camera and chimp-your-LCD to set things up, but that’s an awful way to work.

ISO-EV-Duration

In photographic study, proper exposure is achieve when you have the right balance of light intensity, exposure duration, and sensor sensitivity (digital sensor of film).

Light intensity is just that. How bright is the light that’s reaching the sensor. This is affected by the light source (power of the light) and the size of the lens opening (F-stop).

Exposure duration is based on your shutter speed. It can also be based on the flash duration.

Sensitivity is usually based on an ISO value. (ISO values are defined by the International Organization of Standardization, who adopted ISO as their short name because of the Greek word, “isos”, which means equal.)

EV is a shorthand for exposure value that was developed in the 1950’s as a way of quickly making shutter speed and F-stop value changes.

Dragging The Shutter

This term implies making your shutter speed slow – almost to the point of making blurred images – knowing that a short flash duration will keep the main subject nice a sharp (or un-blurred). It’s a technique for working in dark areas where the flash can’t full cover what’s being photographed.

This technique could also be used in sunset photo situation where you need to need a slower shutter to get a properly exposed sun/sky and have the main subject lit by the flash making a natural looking result. This requires lots of practice and, possibly, some filtering of the flash.

Color Correction

Different light sources have different color temperatures. A color temperature is simply the mix of red-green-blue components in white light. An incandescent bulb typically has a lot of red. Noontime sun has a mix that most would consider “normal”. A blue sky will have more blue, even though its light comes from the normal sun.

The word “color temperature” comes from the lab measurements/systems used to determine the color mixes, and then quantify them. The system is based on burning certain materials, measuring the light, and assigning a number to the result. Science likes experiments and repeatability. So, scientist devised a scale (in Kelvin degrees) that can specify the values of color components in white light. We get 5600K for noon sun, 6000+ for blue sky, 3000 for incandescent. Your digital camera’s white balance settings can match these numbers. (Or, if you are using film, then the film will be daylight balance or tungsten balanced.)

Working in a mixed color temperature environment can sometimes be tricky. A daylight balanced scene (like if you are using a flash as the main source), that also has “mechanicals” that are tungsten (think table lamps that are both lit and in your scened), will give you a mixed situation. This could be a good thing if the mood this mix creates is what you want. If it’s not, then you need to change the light temperatures with filters.

It could be pleasing to have warm tones in a normally daylight balanced scene. Going the other way is just too weird. If you are photographing using a tungsten balanced set, and you have strong window light sneaking in from outdoors (which you may not see right away because it would be buried in reflection), your result could be too unnatural. Your eye makes adjustments and you don’t notice such things when you’re shooting, but when you look at the results, you’ll notice the weird blues. Then it’s too late.

One way to handle color corrections is with filters.

How You Can Use It

If you looked at the cheat sheets above, you may notice that some of the examples include how the lights were set up. The number of lights and their direction is generally main, fill, hair, kicker, and background.

Main

This is usually the brightest of the lights and is on the main subject. Depending on how you manage the direction, the light can be a big part or a smaller part of the final image. That’s the artistry that’s up to the photographer’s bag of tricks.

Fill

Fills in the shadows or darker areas of your subject. Here’s a nice article from Explora that explains how to use camera mounted electronic flash for fill. In the Technique section of this workshop instructions, we go into more detail about fill light and lighting ratios.

Back Light (Hair Light)

This helps separate the subject from a background. It’s very useful when a low-key image (dark background) is being made. You don’t need this for high-key as the subject is usually against a bright, white background, so separation isn’t an issue. Some photographers still use a back light, though, to highlight other aspects of the subject. Usually this is handled more as a kicker light.

Kicker

Useful to emphasize edges of a subject. Sometimes called rim light.

Background Light

Depending on the lighting ratios and effects, you may need to light the background. You can do this to create a pattern on the background as well.

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