Light and the Human Eye
Written by: Digital PhotographyPhotography Lesson #2
The human eye looks basically like the crude drawing below. The lens at the left side of the eye focuses light rays onto the retina at the right. The retina converts light rays into electrical impulses that are sent to the brain. Our brain then tells us we are seeing a bit of light.
Both digital and film cameras have a lens in front to capture light rays. Light rays enter through the lens to the film, or digital sensor; both of which are sensitive to light. Instead of jumping ahead of ourselves, let’s get back to the basics.
About Light Rays
We have different labels for describing the rays we see. Here are a few basic ones:
Transmitted Rays
When you look at a stop light the top light is red, the middle is yellow, and the bottom light is green. That light is transmitted by putting a light source behind a colored filter.
Direct Rays
When you look directly into the sun, a camera’s flash unit, or a flashlight you are looking at direct light. The light you see is coming directly from the source.
Reflected rays
When you look at anything, you can see that object because direct light is shining on it and being reflected back into your eyes.
Ambient light:
Think of ambient light as stray light – light rays that are being bounced around from all sorts of sources. If direct or reflected
light on the subject is stronger your subject will appear clearer and less hazy.
Available light
Available light simply means whatever light is present when not using a flash or other sources of light.
Understanding Color
The COLOR of the subject is determined by the color of the light source and the color of the subject.
Photographic film records light as it actually is. Your eye/brain, however, will always correct light back to
“normal”. Your brain is constantly compensating.
That is … if you are inside a place that is lit with light bulbs, those light bulbs actually transmit a reddish-brown light and white objects will be recorded on film as reddish-brown. However your brain will correct that light and a white object will appear white.
Same thing happens inside a place illuminated with fluorescent bulbs. Fluorescent bulbs actually transmit an ugly greenish-yellow
light, but your brain corrects that light and it appears white to your eye. Film records that light as greenish-yellow.
Fluorescent light contains only enough green and yellow light to photos turn out a bit “off” in color. However, by using a magenta filter in front of the lens, the overall lighting is more natural and “warm”.
We will discuss this at length later on. Right now just understand that it happens.
RED light rays only contain red because it is a primary color. So GREEN light rays only contain green, and BLUE rays only contain blue. Again, that is because these are the PRIMARY colors.
Secondary colors - magenta,cyan, and yellow are considered SECONDARY colors because each one is a mix of two PRIMARY colors. Mixing PRIMARY & SECONDARY colors will give you TERTIARY (third tier) colors …. making up all the visible
colors in the spectrum.
You can see how PRIMARY colors and SECONDARY colors mix from the chart below:
Here’s another image to show you how using the primary colors, red, green and blue, you can produce the secondary colors.
Do Not Worry, there will be no test on this. Just read it and think about it for a while. This concept can be a little confusing as in school we learned that the primary colors are different. We must remember that color in the printing world is what we learned in school, but color combinations are different for light. For photography, we must learn the colors of light, not the colors for printing. In photography we are talking about RGB or colors of light that join together to make white, whereas in print all primary colors joined together would create a neutral color, or gray.
Right now let’s go on to photography lesson #3: Lenses
Love the site.. one correction though .. Yellow is primary color and green is secondary color (yellow and blue makes green)
Frank, glad that you like the site! What we’re talking about here is light rays. You are correct in that yellow and blue make green in the printing world. When you are using pigments or dyes to create different colors. This is commonly referred to as CMYK short for cyan, magenta, yellow, and key (black) color space. With light however the color space is Red Green Blue (RGB) to which the
primary colors are red, green, and blue.
This was new learning experience for me (about the definition of primary colours) and it helps explain a few definitions that previously i had trouble with. I love learning new things that challenge my previous concepts.
Thanks
very easy to understand, no bumble jumble here!
green is no a primary color, yellow is. You can’t mix any two colors to get yellow, but if you mix yellow with blue it will give you green. I can’t believe you have this info wrong…
Rasha, you’re getting confused with the difference between additive color schemes, and subtractive color schemes.
The primary colors for the additive scheme is red green blue. This is how light works. Combining any of the red green blue colors in various levels, produces the secondary colors cyan magenta and yellow. See the new image at the bottom of the lesson that I added. It shows how shining red, green and blue lights produces the secondary colors.
It may seem opposite to what you’ve been taught in school, but this is fundamental to the understanding of light.
thanks for your lesson, this is really helpful and easy to understand.
its really interesting nd simple..
Rasha you know there are more then one or 2 different colour wheels out there. One being for Light…and the one your thinking of is pigment or paint mixing. Mixing all the colours of paint turns black, mixing all the colours of light makes white. By mixing RGB thats how your tv or computer monitor pixels make you see colour.
WoW! That’s amazing – you learn something new every day! I never knew there was a different colour wheel for light! When I read this I was indignant – “they’ve got it wrong!!”, but now I see and understand the painting mix making black and the light mix making white – it all makes sense
Wow! This greet, I know for explaining something in asmple way first you have to understand it deeply and only then you can explain it in simple word. Thank you, i enjoyed this.
This site is very helpful. I’ve begun an interest in photography and this site makes everything seem clear and easy to understand. I’ll be reading in the future.
I think many of you are confused between the primary colors and the primary pigments. RGB are the colors and CYM are the pigments…
You make it easy to understand. Thanks! Looking forward to continued learning.
Thank you to this site it is so easy to understand. I have decided to look into getting my degree in Photography and decided to read up on it before I decided and payed for the tuition, after reading this site I have decided to go ahead and do it. I am going to use this site to help me through my studies and so that I can get a jump start on everything before my classes start. Thanks again.
Thank you so much for this clarification. Being a professional fine artist and aspiring to be a professional photographer, this is a crucial distinction for me. It is interesting and interactive and not like a boring classroom. Thanks everyone…
Easy to read so far, back to basic and solid my understanding before I jump to advanced level. Will stay and learn step by step. Thank you
I’ve been guided poorly through some basic photography concepts in the past, however the RGB was one of the concepts that never truly fixated in my mind because I never fully understood it; the site was helpful but provided me with the same information I had gotten previously. It wasn’t until I read the Admin clarficiation to Frank from 05.07.09 @ 05:52 PM that it finally sunk in. I was reminded that the primary colors we are taught in school are for the printing scheme, not lighting scheme; the difference can be fully understood when remembering that when the primary colors are added in each realm they give opposite results: whie in the light scheme and black in prinitng. This was the most helpful clarification yet and I believe i should be included in the article to relieve a common confusion.
I’m interested in improving and understanding how to use my camera properly so that I can take good photo’s so I looked on the web to see what I could find. This is just the type of course I was looking for. I’m going to complete each lesson and not skip any. Reading the questions and amswers help enormously also. I really can’t wait to get out there and take more photos!
i have always been interested in photography but it’s only been a year or two since i’ve actually started doing photography myself…the more i went out and the more i took photos the more i got interested in it…and ever since then i’ve been wanting to learn photography…and i m so glad i could finally find a site where the lessons are designed for easy understanding…
looking forward to continuing the courses…
Wowwww!! I’ve just recently developed a deep passion for digital photography but my smile turned Upside down while checking the prices of online courses! But visiting this site was a big “phew”!!
Thanks!
Thank you so much for providing legit professional knowledge at no cost! You people are every budding photographer’s angels!
The information on colours is really something that has amazed me. To begin photography, I reckon, we must understand the difference between printing colours and the light colours. And I must be honest, I was not aware of the use of colours of light rays and printing. The clarification given is really wonderful, and I must say this is the website I was searching for to start and learn photography.
This is an awesome site, with great information. It has helped improve my game with just the simple suggestion on the first page! wow!! I have one question though that I’m not clear on. Sometimes, depending on my medical condition I have a hard time focusing. Glasses are not always good for me because of the varying nature of my eyes. If I’m in one of those blury moments, while shooting w/my camera and I focus the subject through the SLR’s view finder, because my eyes are off will the picture develop out of focus even though it looked right to me while taking the shot
Eddie, I’m not sure about the nature of your eyes, but you may just have to learn to rely upon the auto focus of your camera by using the spot focus to have what you want in focus in the center of the viewfinder, and then moving the camera while keeping the shutter button half way depressed. Sounds like you’ve just got to practice and become familiar with how you see.
Thank you for this site. Its like having a classroom in your home. One question, will there be a chance to share our photos with each other?
We’re always looking to improve the site and that’s on our list of improvements to make. For now you can share your flickr account and get feedback that way.
I have learned something even with the first lesson … although I am a Physics major and I understand the difference between colors of light and colors of pigments, I didn’t quite realize that the camera captures the correct color and the brain actually “corrects” the true image. I always thought that there is something wrong with all these cameras which capture “cold” or unrealistic images.. just like you have illustrated in the pictures here. Thanks for the great lesson.