Glance at the summary firstThe summary from the end of the lesson, as a road map before you start reading.
Continuous light makes it possible to shoot what you see and to shoot video; you see the direction of the light and the shadow without pressing the shutter. Flash, on the other hand, freezes motion on its own because it fits its light into a very short moment, and is strong enough to compete with the sun; the modeling light in studio flashes builds a bridge between the two worlds. When choosing an LED you look at color rendering, adjustable color temperature and flicker; a light with poor color rendering shifts skin toward green or pink tones that don't correct with white balance, which is why skin is checked with a gray card and against the person's real color.
Learning goal
You will be able to decide whether to use a flash or a continuously burning LED in a shoot, by looking at which matters more at that moment: seeing the light in advance, freezing motion, video or power. You will compare the ease of continuous light, where you shoot what you see on the screen and with your eye, with the power of flash, which freezes motion and competes with the sun by giving very high light in a very short time. You will check an LED panel's color rendering, its color temperature setting and the flicker seen in some cheap lamps, and see what kind of bridge the modeling light in studio flashes builds between the two worlds. You will notice how a light with poor color rendering leads to color shifts on different skin tones, and choose your source accordingly.
The question
Your cousin has put the violin portrait in their file, and now you are back in the study for the two-minute playing video they will send to the panel. You mount a rectangular LED panel borrowed from a friend on a stand and turn it on. The first thing you notice is that you can now see where the light falls without pressing the shutter: when you turn the panel a little to the left, you watch with your own eye how the shadow on their cheek lengthens. The video shoot starts without trouble too. But when your cousin moves into a fast passage, in the photos you shoot with the same light the bow and fingers come out blurry; when you shorten the shutter speed, the frame goes dark. On top of that, your cousin starts to squint, and on the screen their skin looks a little greenish and pale.
Flash or LED? Can a continuous light take the place of a flash, and if not, which one should be chosen for which job?
Context
Throughout this module we got to know the flash: a short burst, an exposure independent of the ambient light, a power that can compete even with the sun. But the flash always had one weakness: you could see the light only after shooting, and in a shoot that keeps recording it stayed dark. Continuous light, as its name suggests, removes these two problems.
Today, when continuous light is mentioned, LEDs most often come to mind; they are light sources that are light, run cool, can be battery-powered and have adjustable color temperature. But not every continuous light is of the same quality, and it can never fully do some of the jobs the flash does. This lesson compares the two tools not as rivals, but as two tools designed for different jobs, and leaves the choice to what the shoot needs.
Simple explanation
What does continuous light make easier?
Continuous light is an artificial light source that burns without interruption throughout the shoot and lights the subject. An LED panel, on the other hand, is a continuous light source made of many small light-emitting diodes, usually flat and rectangular in shape. Some panels run on batteries, and some can have a diffusing fabric or a softbox attached in front.
The biggest advantage of continuous light is that you shoot what you see. You see the direction of the light, its hardness, where the shadow falls and the shine on the face with your eye and on the camera's screen before pressing the shutter. You can slide the light a finger's width and watch the result right away. The camera's screen and light meter also measure this light directly; you don't need to shoot a test frame and make a guess as with flash. This is a great convenience, especially for those just learning light.
Video also asks for continuous light. A flash burns only for an instant; video, on the other hand, records many frames per second, and every frame needs light. If you need to do photo and video in the same shoot, continuous light is the only option.
A modeling light is a small lamp found in some flashes, especially studio flashes, that burns continuously to show in advance where the flash's light will fall. This lamp contributes almost nothing to the exposure, but it builds a bridge between flash and continuous light: you see the direction of the light in advance, then shoot with the flash's power.
At which job is flash stronger?
A flash fits its light into a very small fraction of a second; that is why the brightness it produces in that short moment is much higher than what a continuous light of the same size produces. This has two results. The flash freezes motion with its own short duration; with continuous light, on the other hand, you need to shorten the shutter speed to freeze motion, and every shortening reduces the light. In your cousin's fast passage the bow came out blurry, because the LED panel's light wasn't enough for a short shutter speed; you are forced to raise the ISO or open the aperture.
Power becomes even more noticeable outdoors. To fill a face under the sun or to overpower the sun, a flash is most often enough; a continuous light that would do the same job would be very large, heavy and expensive. A small LED panel, in daylight, often isn't even noticed.
Continuous light also has a price on the person. When a bright light burns continuously, the eye is bothered, the person squints and their pupils shrink. A flash, on the other hand, burns only for an instant; before and after it, the eye stays open to the dimness of the setting. In a long portrait shoot, moving the continuous light a little farther away, passing it through a diffuser, or dimming it in between relaxes the person.
Why does an LED's color matter?
Not every LED produces the same light. Color rendering is the measure of how accurately a light source shows the colors of objects compared to a reference light such as daylight. This is usually expressed with a number at most one hundred, called the color rendering index, CRI in its English abbreviation; the reference light is taken as one hundred, and as the value rises colors look more faithful. But this number doesn't reflect every color to the same degree; a cheap LED, even if it carries a high value, can be weak in certain colors, especially deep reds.
A light with poor color rendering produces shifts that can't be fully corrected with white balance. On skin this shift stands out most, because the eye is extremely sensitive to the color of a face. On dark skin, a low-quality LED can pull the warm brown toward a greenish or ashy gray and erase the skin's red undertones. On light skin, on the other hand, the face can shift to a pale, sickly green or, conversely, an artificial pink. The simplest way to check this is to put a gray card next to the face and have the camera take it as neutral, then compare the skin with the color the person has in daylight. If you still see the shift, the problem isn't in the white balance but in the light itself.
Adjustable color temperature is an LED's ability to shift its light from a warm incandescent tone to a cool daylight tone. This makes it easier to match the panel's color to the ambient light in a room with mixed light. Some cheap LEDs, on the other hand, dim by switching the electric current on and off rapidly; this leads to a flicker the eye doesn't notice, and it can show up as bands in the frame at short shutter speeds or in video (Lesson 8.4). Shooting tests with a few different shutter speeds before using a panel reveals this problem early.
Visual evidence
In the study you first put a gray card beside your cousin's cheek and set the white balance against it. The card looks neutral, but your cousin's dark skin is still slightly greenish; the reddish warmth in their cheeks has disappeared, and their lips are pale. The panel you borrowed has poor color rendering. When you swap the panel for another friend's higher-quality panel, at the same white balance the warmth in the cheeks comes back and the lips return to their own color.
You shoot the video with this panel, with a diffusing fabric attached and a little away from your cousin; your cousin no longer squints. For the photo of the fast passage, on the other hand, you turn off the panel and put the flash with a small softbox in the same place. The bow and fingers come out sharp, and you can keep the ISO low too. Two lights in one shoot: continuous light for the video, flash for freezing motion.
Common mistakes
Common mistakeTrying to freeze a moving subject with a small LED panel.
The light isn't enough for a short shutter speed, and the frame either goes dark or comes out blurry. The fix: if you need to freeze motion, use flash, or open the ISO and aperture accordingly.
Common mistakeTrusting a cheap LED's color and not checking the skin.
Green or pink shifts that don't correct with white balance remain. The fix: set the white balance with a gray card and compare the skin with the person's real color; if the shift continues, use a source with higher color rendering.
Common mistakeHolding a bright continuous light close to a person's face for a long time.
The person squints and gets tired. The fix: pass the light through a diffuser, move it a little away, dim it in between.
Summary
Continuous light makes it possible to shoot what you see and to shoot video; you see the direction of the light and the shadow without pressing the shutter. Flash, on the other hand, freezes motion on its own because it fits its light into a very short moment, and is strong enough to compete with the sun; the modeling light in studio flashes builds a bridge between the two worlds. When choosing an LED you look at color rendering, adjustable color temperature and flicker; a light with poor color rendering shifts skin toward green or pink tones that don't correct with white balance, which is why skin is checked with a gray card and against the person's real color.
Mini assignment
Try the following using the LED panel you have, or a strong desk lamp, side by side with your flash.
- Shoot the same portrait first with the LED panel, then with the flash, putting the light in the same place; note how much seeing the light in advance with the LED made the setup easier.
- Shoot a moving hand or a swinging object first with the LED, then with the flash; compare whether the motion freezes.
- Set the white balance with a gray card and compare the color of the skin under two different LEDs, or under an LED and window light.
- Dim the LED and shoot with a few different short shutter speeds to check whether there are flicker bands in the frame.
Check yourself
- Can you say whether a shoot asks for flash or continuous light by looking at what the shoot needs to do?
- Can you explain through shutter speed and power why motion stays blurry with continuous light?
- Did you compare the color of the skin under different lights with a gray card and against the person's real color?
Glossary
| Term | Short definition |
|---|---|
| Continuous light | An artificial light source that burns without interruption throughout the shoot and lights the subject. |
| LED panel | A continuous light source made of many small light-emitting diodes, usually flat and rectangular. |
| Color rendering | How accurately a light source shows colors compared to a reference light; most often expressed with CRI. |
| Modeling light | A small lamp that burns continuously to show in advance where the flash's light will fall. |
| Adjustable color temperature | An LED's ability to shift its light from a warm tone to a cool tone. |
Mini quiz
1. What is the most distinct advantage of continuous light over flash?
- A) Seeing where the light falls before shooting, and being able to shoot video
- B) Freezing motion better
- C) Competing with the sun more easily
- D) Preventing red-eye
2. If you can't shoot the bow of a fast-playing violinist sharp with an LED panel, what is the basic reason?
- A) The LED's color temperature
- B) The panel's rectangular shape
- C) Continuous light not being strong enough for a short shutter speed
- D) The white balance being wrong
3. Even though you set the white balance with a gray card, a dark skin still looks greenish and ashy. What is the most likely source of the problem?
- A) The aperture being wide open
- B) The camera's file format
- C) The shutter speed being long
- D) The light source's color rendering being poor
4. What is the modeling light in studio flashes for?
- A) It raises the flash's power
- B) It shows in advance where the flash's light will fall
- C) It is used as the main light in video
- D) It reduces red-eye
Answers
- A — Continuous light is seen on the screen and with the eye; video also needs light in every frame.
- C — With continuous light, motion is frozen by the shutter speed, and a short shutter speed needs a lot of light.
- D — The shift of a light with poor color rendering doesn't fully correct with white balance.
- B — The small, continuously burning lamp shows the direction of the light; it contributes almost nothing to the exposure.
Summary card
- Continuous light: shoot what you see; the only option for video.
- Flash: very short and very strong; it freezes motion and competes with the sun.
- The modeling light shows the flash's direction in advance.
- When choosing an LED, look at color rendering, the color temperature setting and flicker.
- Compare skin with a gray card and against the person's real color.
Bridge to the next lesson
When you shifted the panel's color temperature in the study and created a warm evening mood, your cousin started to look completely different in the video. A photographer friend suggested attaching a thin colored sheet in front of the flash to throw a purple light on the back wall, and matching the flash's white light to the room's warm lamps. Could changing the color of light, besides adding atmosphere to a photo, also be a way of balancing mixed light? How do you make colored light? The next lesson tells about colored gels, creating atmosphere with them and balancing mixed light; and with the module's project, it completes working with flash.