Category Archives: Light

7 Measures Of Brightness

The Value of Light or Measures of Brightness

To begin with we have a specific brightness of light at any given time. Different times of the day, conditions, cloud cover etc. provides for changing light values. It is just like the temperature, it is never static, but it is totally measurable. At 72 F or 20 C we are comfortable, if we increase the heat to 100 F or 37.8 C we are too hot, and when it is 20 F or -6.7 C we are cold.

We can measure light and we say that the “light level” or “light intensity” is “X”. Light is measured in the European version as “LUX” or the North American format of “foot candles”. A foot candles measurement is the amount of light that one candle can emit at a distance of one foot. Naturally, when you have more candles it will be brighter. Another measurement that we know of when dealing with artificial light, is that light loses its brightness inversely proportional to the square of the distance. In other words, if we have one-foot candle power at one foot, by being another foot farther away the light level is not halved but quartered. We’ll get into this more when we discuss flash photography. For now, you can see various light levels outdoors under different conditions.

Light Level or Illuminance, is the amount of light measured in a plane. The work plane is where the most important tasks in the room or space are performed.

MEASURING UNITS LIGHT LEVEL – ILLUMINANCE

Illuminance is measured in foot candles (FC) or LUX ). A foot-candle is actually one lumen of light density per square foot, one lux is one lumen per square meter. Condition Illumination

• LUX = FC (10.752)

• FC = LUX / 10.752

COMMON LIGHT LEVELS OUTDOOR

conditions of illumination

Normal Exposure

Normal Exposure

1 Stop or unit of Light Overexposed

1 Stop or unit of Light Underexposed

Determining the proper exposure.

Ok, let’s get back to determining proper exposure. As we discussed in our last post, the camera sensors are geared to read the part of the scene you are metering as if it looked like it was 16% gray.  If what you are looking at is white, then the picture would turn out darker because the sensor thinks it is light gray. Opposite to this, when you are looking at something that is dark and the camera thinks it is 16% gray, the picture would turn out too light.  This is where your creativity and imagination kick in.

If you want as close to the “best” exposure as possible you would look at the scene and imagine it as a black and white scene and then pick an area that looks close to 16% gray and use that area to meter for the best light level reading. You now get to turn this “level” into the exposure that you want to use to create the image you want.

How do we translate the exposure reading into the image we want?

Now we get into the trinity of photography; aperture, shutter speed, and ISO. By properly adjusting these three elements you will get the exposure you. That we will discuss in our next blog.

The Belagio

Night at the Bellagio – always a tough exposure

We hope this will help you get the images that you imagined and deserve.

Good shooting and understanding light!

Bob and Chuck

We would love your comments – let us know.

What is the colour of light

What is the colour of light

In the last post we talked about the properties of light, today we are going to look at “What is the colour of light?” No pun intended, ok maybe a little bit. You are probably wondering why we are spending so much time on this stuff? The reason is that in order to take great pictures you need to understand clearly why you are not getting the results you had hoped for.

Yes, all the technical information that we have covered and will be covering in greater detail is important. But the human element, how we handle our equipment, how we align things compositionally, and finally how we see a scene is the most important,

 

The electromagnetic spectrum

 

Light is energy that travels through space at a rate of 186,000 miles per second and comes in a packet called a photon. Each of these photons travels in a wave that is seen as a different colour depending on the length of the wave it is travelling on.

We all know that the light coming from the sun is a rainbow of colour, but we see it as white. Within this ray of light, there are many types of light in the forms of various wavelengths. From the illustration above you can see a variety of them. We can only see what is called the visible light spectrum. Red has the longest wavelength and each colour gets shorter from there: orange, yellow, green, blue, to one of the shortest violet.

What happens when the light gets absorbed or refracted?

A good example would be, “Why is the sky blue?”

The atmosphere is full of various water and gas molecules. These molecules cause the incoming sunlight to be scattered or redirected. We have talked about the length of the wave and now know that blue has the shortest length and the others are longer with red being the longest. This means that blue is easier to scatter than the red so the blue is scattered all over the place and the other colours get through to the surface and we get to see the sky as blue.

At the other end of the spectrum, why is water blue? Water absorbs warm colours which are long wavelength light and scatters the cooler colours (short wavelength light). Red light is absorbed strongly, and the blue light has the deepest penetration depth. That’s why we get blue water.

The opposite occurs early in the morning and at sunset. The shorter red wavelengths hit our eyes because they are not scattered while we don’t see the blue wavelengths because they are scattered. What we see are beautiful warm orange/red sunrises and sunsets.

How do we see colour?

White light consists of blue-violet, green, and red, when these are all mixed together they produce white light. These are known as the primary colours. True enough, when an artist works with pigments and mixes these together they are far from white. But we are working with transmitted, reflected, dispersed, refracted, and absorbed and when the primary colours are used in this way they mix together to make white light. In our investigation of light, it is the absorption of colour that we are concerned with. It is the absorption of light that make the colour. Objects will absorb, transmit, or reflect light falling upon them. We cannot see the light that is absorbed, only that which is reflected.

This brings us to the next concept in light, that which is called Colour Temperature

 

We need to understand that the colour of light is not consistent because of the dispersion of the wavelengths at a different time of the day or the light source that you are using to take pictures with. As we saw with blue skies and sunsets the amount of the various wavelength being scattered caused the colour we see. Similarly, light sources have a variety of wavelengths in their chemical makeup that changes how a camera will record the colours. The eye does not see how a camera sees. In our brain, we have recorded what colours should look like and when we process the scene we will see it as we think we should see it. For example, a white shirt in bright sunlight will be white, but under tungsten light it is orange, and under fluorescent light it is green. All the while the brain tells us that it white and we see it as white.

The need for an accurate means of measuring the colour of the light was realized by the English scientist, Lord Kelvin. When you put an iron poker into a fire it first turns a dull red and then glows to a brilliant red and finally turns white. Lord Kelvin produced this effect and standardized it and then identified the colours by the temperature of the metal at that instant.  The temperature is described as Kelvin degrees.

This is the point where you can say to yourself, no wonder when I take pictures inside the colours are wonky. Or on the opposite extreme, when you see a fantastic sunset and you take a picture of it the colours are not as vivid as you “see” it.

Your camera has a variety of settings that control or allow various colour balancing. Several of the common symbols for these options are seen below:

 

AWB

“AWB”, or auto white balance is the standard go to. It automatically tells the computer to reproduce the colours to make it look like the picture was taken at high noon – 5500 k. So, the nice glow of the fireplace on the kids’ faces or that vivid sunset is lost with the AWB.

 

Custom

“Custom”, allows you to set your own white point. The best way to do that is to use a “Gray card”. A grey card is a photographic card that is covered with a neutral grey set at 18% on the gray scale. A grey scale is a scale that goes from white through various stages of grey all the way to solid black. White has a value of 255, while black has a value of 0, and the greys have a value in the middle.

All light meters are set up to take a recording of the light as if it were looking at a 16% grey patch. We will discuss reading light in another post. Because if you think of it logically, when you are taking a picture of snow and the light meter is thinking that it is looking at 16% grey, your picture will look muddy, or at least grey, lol.

Why do they use a grey card? Because when you use a grey card it is easier to see slight colour, tonal, and contrast shifts.

Back to our grey card. Take a picture of the grey card in the sunshine between 11:00 am and 1:00 pm and save it on your camera. Make sure that the card is evenly lit. Use the automatic setting. Fill the screen with the grey card.

For Canon users:

  1. Find the “custom” setting in your colour balance menu and it will ask you to choose an image.
  2. Choose the image you just took of your grey card and choose “Ok”.

For Nikon users,  the custom setting is actually called “Pre” for Pre-set Manual White Balance setting.

  1. Set your camera to the automatic exposure mode
  2. Fill the viewfinder with your grey card
  3. Select white balance, press ok
  4. Select PRE, press the Multi Selector right,
  5. Select Measure, press OK
  6. Select Yes and press OK

for other camera makes and models look in your instruction manual.

Kelvin

Although it takes a bit more thinking, using Kelvin is much easier the more you use it. Not to forget that you will get the results that you are aiming for. Basically, memorize the “Colour of Light”  chart above and set your Kelvin setting to the temperature of the light you are working with. If you are photographing with candles you would be around 2000K, outside in the sunshine 5500K, in the shade approximately 7000K. Those are rough parameters. Another way to think about it would be; if you want cooler colours to go higher up the scale 7000K – 9000K, if you like warmer pictures 2500K – 4000K. As mentioned back in one of our earlier posts – you are in control of your image. Make sure that what you see is what you will get or create.

Tungsten

This setting is the one you would use when taking pictures in your home when you have tungsten bulbs in your lamps. Tungsten bulbs are the old fashioned normal light bulb that is a yellowish/orange colour.

Fluorescent

Fluorescent lights have an ugly green, cool colour. You would use this setting to get rid of that shade.

Daylight

This may sound silly but daylight means you are using pure sunlight and are away from shady, or areas that would get a colour cast reflected from grassy area or buildings.

Cloudy

Naturally we are talking about an overcast, cloudy day that offers a cool colour. This will warm up the image for you.

Flash

Each flash unit has a colour temperature of its own, but usually they are considered “cool” colours. So this setting will warm it up for you.

Shade

We come to the last option, shade. Shady areas often are cooler and have tinges of green or the colour of the object that is creating the shade. Once again we see a warming effect.

AWB                                      Kelvin 5,000                                  Kelvin 2,000

indoors it would look good           indoors it would look good

blue removed                           yellow removed

Tungsten setting                             Fluorescent                                         Daylight

yellow/orange removed              red/green removed

 

Cloudy setting                                      Flash                            Shade – some blue removed

We hope this will help you get the images that you imagined and deserve.

Good shooting and pure colours!

Bob and Chuck

 

 

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Best Compact Cameras

Photography and light

Photography and light, the dynamic duo.

You can’t have a photograph without light. Photography has been credited, at least the concept of photography, to the Chinese around the fourth century BC. They had a box which later was called a “camera obscura”, a Latin term meaning “dark chamber”. Basically, it was a box with a small hole pierced in one side, which allowed light in the box. The light would shine on the opposite wall to the opening showing an inverted image of what was reflected from the outside.

When did photography start?

It wasn’t till the 1800s that actually capturing an image on light-sensitive material was made possible. Joseph Nicephore Niepce is credited to creating a permanent image, called a heliograph, around 1826. A heliograph is basically a piece of highly polished pewter covered with a concoction of bitumen and lavender oil. Apparently, bitumen which is a kind of asphalt is light sensitive.

Credit: Wellcome Collection

The first heliograph of Niepce looking over his balcony.

Heliograph means writing with the sun – helios = sun, graphein = writing.

Today we have something similar, a box with a hole in the lens which when the curtain inside the camera body is opened allows light in. The light shines on a light-sensitive surface such as film or digital sensors and leaves a lasting image. Like the original camera obscura, the image is still rendered upside down.

How are images saved?

Film contains light-sensitive silver-halide crystals whose silver ions clump together when light reaches them; these clumps of silver form the image on a photographic negative. As more light strikes the film, more silver ions clump together, and the image on the negative becomes darker.

Instead of film, a digital camera has an array of image sensors that capture incoming light rays and saves them as electrical signals. it’s simply an electrical charge much like the static electricity that builds up on your body as you shuffle across a carpet on a dry day. As the light comes in and hits the sensors, the computer in your camera measures the colour of the light coming in as well as it’s brightness.

These sensors are typically called pixels. A pixel is only given size and shape by the device you use to display or print it. The information of these millions of sensors is then stored as a long string of numbers. Naturally, the more sensors you have, the higher quality image you will get.

There are three types of sensors; a CCD or charged coupled device, a CMOS image sensor or complementary metal-oxide semiconductor sensor, and the Foveon X3 image sensor. Each has its advantages but suffice it to say that there are millions of image sensors used to create a digital image.

The advantage the Foveon system is that is unlike a digital sensor which only records one colour at a time, either the red, green, or blue; it has three layers and directly captures all the colours and densities to give a richer more detailed image.

But here is the big rub.

What and how our eyes process a scene is different from how a camera does.

In fact, that is the number one reason why people are disappointed with their pictures. It doesn’t look like what they remember they saw or are seeing.

What is light?

We all know that this magical entity called ”light” comes from the sun and bounces off of the item you are looking at lets you know the shape (because it is bouncing off of the things around the item you are looking at) and the colour by absorbing all of the colours it isn’t and reflecting the colour back to that it is.

We know from our early science classes that English scientist Sir Isaac Newton and Dutch physicist Christian Huygens came up with the idea that light was made up of particles and waves in the 17th century. This conundrum of which it is, still hasn’t been resolved.

The18th century saw Danish scientist Orsted seeing that changing electric fields creates a magnetic field. Later English scientist Faraday found that a changing magnetic field creates an electric field. Scottish physicist Maxwell brought the two concepts together into “electromagnetism”. But Maxwell took it a step further and brought all these ideas together to explain light.

Light is electrical fields combined with a magnetic field that travels through space as a photon which has no mass and moves at high speed. That’s why we think of a photon as a “unit of light” and an electromagnetic wave as a “light wave”. That is why light can be reflected and refracted.

How do we see colour?

The first question we need to answer is how do we see? In very simple terms, under low light conditions the rod-shape receptors in our eyes registers black, white, and grey tones. That is why our night vision is sharper but only a little colour. The cones in our eyes (there are three types of cones) are the primary receptors and under normal light give us normal sight and the sensation of colour. These electrical charges are sent to the brain and interpreted as an image with the colour that is reflected. The human eye is only sensitive to the red, green, and blue wavelengths.

We get to see just a little bit of the wavelengths that are transmitted. The length of the “wavelength” determines the colour that we see.

The combination of all the visible wavelengths combines to give us “white light”.

The shortest of the wavelengths is violet while red is the longest of the wavelengths. As I mentioned earlier, white light hits an object and all of the wavelengths get absorbed but the one which is reflected back to us, which is the colour of the item.

The sky is blue because blue is the shortest wavelength and it is scattered around the sky by all the molecules in the Earth’s atmosphere. Likewise, because blue has such a short wavelength, it is totally scattered out and away when it has to travel so the farther distance early in the morning and later at sunset, giving the sky a warm red and yellow tone.

Think about these things as you go take pictures. We will take you to the next level in our next post.

To your great shots

Bob and Chuck

We would love to hear from you. If you have any questions or comments let us know.