Unit C Lesson C9 Eyes and Cameras
Completion requirements
Lesson C9: Eyes and Cameras
Video Lesson
Cameras collect light and form images in a similar way to eyes. Watch this video to learn more about the similarities between cameras and eyes.
Lesson C9: Eyes and Cameras
Figure C.3.9.1 ā Reflected light from the eyeās blood vessels causes red eyes in photographs.
Figure C.3.9.2ā Red eyes occur when a flash is close to the cameraās lens.
Figure C.3.9.3ā Cameras have a double-flash system to help reduce red eye in photos.
Reading and Materials
for This Lesson
Science in Action 8
Reading: Pages 231ā234
Materials:
There are no additional materials required for this lesson.
Red Eye Photos
Sometimes eye pupils appear red in photographs. Red-eye photographs usually happen in a dark setting where camera flash is used to add extra light.
In dark conditions, an eyeās pupil opens up wider so more light can enter. A camera flash produces lots of light, which enters the wide-open pupil. Some of this light reflects off the eyeās retina back to the camera lens. The retina contains lots of blood vessels to supply nutrients to rod and cone cells. Since blood is red, it reflects red light. This reflected red light travels back out the wide pupil to the camera lens. The reflected red light is detected by the camera sensor, making the eye pupil appear red in the photograph.
To avoid red-eye photographs, some cameras fire a pre-flash before the camera shutter opens with the real flash. The pre-flash of light causes the personās pupil to get smaller, so less reflected light from the retina exits the eye. Professional photographers position flashes far away from the camera lens, usually at an angle to the eyes. This causes a smaller amount of light to enter the pupils, which reduces the amount of reflected light exiting the eyes.
Sometimes eye pupils appear red in photographs. Red-eye photographs usually happen in a dark setting where camera flash is used to add extra light.
In dark conditions, an eyeās pupil opens up wider so more light can enter. A camera flash produces lots of light, which enters the wide-open pupil. Some of this light reflects off the eyeās retina back to the camera lens. The retina contains lots of blood vessels to supply nutrients to rod and cone cells. Since blood is red, it reflects red light. This reflected red light travels back out the wide pupil to the camera lens. The reflected red light is detected by the camera sensor, making the eye pupil appear red in the photograph.
To avoid red-eye photographs, some cameras fire a pre-flash before the camera shutter opens with the real flash. The pre-flash of light causes the personās pupil to get smaller, so less reflected light from the retina exits the eye. Professional photographers position flashes far away from the camera lens, usually at an angle to the eyes. This causes a smaller amount of light to enter the pupils, which reduces the amount of reflected light exiting the eyes.
Watch More
Red Eye Reduction
Watch this video to learn more about what causes red eyes in photographs.
Watch this video to learn more about what causes red eyes in photographs.
Figure C.3.9.4ā ļ»æCone cells on the retina detect blue, red, and green light.
Colour Vision
The ability to see colour depends on the cone cells of the retina. There are three different types of cones, each detecting a different colour of light. The three different types of cones detect red, green, or blue light. The brain interprets combinations of these three types of light as different colours.
Colour-blind people have at least one type of cone that does not function properly. The most common colour-blind condition is red-green colourblindness. In these people, either their red or green cones are not sensitive to light. They cannot tell the difference between red, green, brown, and orange. In very rare cases, a personās blue cones donāt work. These people see the world in pinks and turquoises.
A different and rare colour vision condition is tetrachromacy. In Greek, ātetraā means āfourā, and āchromaā means ācolourā. So tetrachromacy means āfour coloursā. Tetrachromats are people that have four different types of cones. The extra cone allows tetrachromats to see the world in more vibrant shades of colour than most people. Many species of animals are tetrachromatic, but their fourth cone senses ultraviolet light, which humans canāt see at all.
The ability to see colour depends on the cone cells of the retina. There are three different types of cones, each detecting a different colour of light. The three different types of cones detect red, green, or blue light. The brain interprets combinations of these three types of light as different colours.
Colour-blind people have at least one type of cone that does not function properly. The most common colour-blind condition is red-green colourblindness. In these people, either their red or green cones are not sensitive to light. They cannot tell the difference between red, green, brown, and orange. In very rare cases, a personās blue cones donāt work. These people see the world in pinks and turquoises.
A different and rare colour vision condition is tetrachromacy. In Greek, ātetraā means āfourā, and āchromaā means ācolourā. So tetrachromacy means āfour coloursā. Tetrachromats are people that have four different types of cones. The extra cone allows tetrachromats to see the world in more vibrant shades of colour than most people. Many species of animals are tetrachromatic, but their fourth cone senses ultraviolet light, which humans canāt see at all.
Figure C.3.9.5ā These six circles each have a number inside. People who cannot see the numbers may be colourblind.
Watch More
Colour Vision
This video explains how the cones in our eyes enable us to see colour.
This video explains how the cones in our eyes enable us to see colour.
Watch this video to learn more about colourblindness.
In this video, two people with colour vision conditions talk about their daily experiences.
In this video you learn that your eyes, and your brain, can be tricked into seeing colour that isnāt really there. Hint: Pause the video at 40s, then use the number 5 and 6 keys on your keyboard to go back and forth between the two images to see the
āfalse colourā.
Lesson Activity
Problem:
Your task in this experiment is to explore a virtual eyeball and watch a dissection of an animal eye on YouTube.
Download:
DOWNLOAD this document. It has diagrams of the eye that you will label. It
also has a space for you to answer the question after you have completed the labelling.
Instructions:
- Watch this video to observe a complete dissection of a horseās eye. WARNING: This video shows the dissection of a horse eyeball.
- Label the diagrams on the document you downloaded with the following main structures in the eye. You may not be able to label all the structures on both eye diagrams, because some structures can only be seen from inside the eye.
- Cornea
- Vitreous humour
- Lens
- Iris
- Pupil
- Optic nerve
- Retina
Analysis Questions:
Think about the following question very carefully. Then, type or write your answer on the document you downloaded. When you have your answer, click the question for feedback.
Think about the following question very carefully. Then, type or write your answer on the document you downloaded. When you have your answer, click the question for feedback.
The vitreous humour is a transparent gel substance so that light can pass through it, to reach the retina.
Lesson Activity
Problem:
Your task in this experiment is to explore how the eye forms images using a virtual vision tool.
Download:
DOWNLOAD this document. It provides a space for you to write your analysis
questions later in this activity. It also provides tables for you to record your observations.
Instructions:
Click here to open the learning object. Work through the following activities. Type or write your answers to the questions that accompany each activity. When you have your answers, click the questions for feedback.
Activities and Questions:
Click here to open the learning object. Work through the following activities. Type or write your answers to the questions that accompany each activity. When you have your answers, click the questions for feedback.
Activities and Questions:
- Click and drag the cross arrow to slide the bird closer and further away from the eye.
ļ»æWhen the bird is far away from the eye, the retina image becomes smaller. The image you see is smaller, but clear. ļ»æļ»æWhen the bird is close to the eye, the retina image becomes larger. The image you see is larger and slightly blurry. ļ»æ
- Turn on the light rays button. Click and drag the bird closer and further away from the eye.
ļ»æThe two light rays always cross in the eyeās lens.ļ»æLight rays travel in straight lines. In order to travel in straight lines, light rays coming from the bird move to the opposite side, forming an upside-down image.The iris causes the lens to change shape. The lens becomes fatter, in order to make the image focus on the retina.
- Turn on the presbyopia button.
Presbyopia is farsightedness, when an image forms behind the retina instead of right on the retina.The image forms behind the retina.When the bird is far away from the eye, the retina image becomes smaller. The image you see is smaller, but clear. Farsighted people are able to see far-away objects clearly.When the bird is close to the eye, the retina image becomes larger. The object you see is larger and very blurry. Farsighted people cannot see close-up objects clearly.
Camera Settings
Many people carry a camera with them everywhere, on their smartphone. Most of the time, these modern digital cameras automatically adjust to the light in the environment. They take a picture that is sharply focused, not too light, and not too dark. An automatic camera does a good job of recording an image similar to how your eyes interpret it.People that work in photography or who enjoy photography as a hobby usually use cameras that are more complex than a smartphone. People enjoy manipulating the settings on these cameras to create interesting artistic effects. The three main settings on cameras are aperture, shutter speed, and ISO.
To learn more about camera settings, click here to Explore with Elsie.
Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your learning.
Unit C Lesson 9 Self-Check
Instructions
Complete the following 6 steps.
Don't skip steps ā if you do them in order, you will confirm your
understanding of this lesson and create a study bank for the future.
- DOWNLOAD the self-check quiz by clicking here.
- ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.
- COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.
-
REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct
any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.
- SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.
- CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!
Be a Self-Check
Superhero!
Self-Check Quiz Answers
Click each of the suggested answers below, and carefully compare your answers to the suggested answers.
If you have not done the quiz yet ā STOP ā and go back to step 1 above. Do not look at the answers without first trying the questions.
Eyes and cameras have adjustable openings to adjust to the amount of light in the environment. Eyes and cameras require just the right amount of light in order to form a clear image. An adjustable opening allows more or less light to enter the
eye or camera.
A detached retina would cause partial vision loss. The light-sensing rod and cone cells in the detached retina section would be unable to send a message through the optic nerve to the brain.
Lenses in eyes and cameras form an image on the retina or on the camera sensor. Light passes through the lens to focus a precise image on the retina or sensor. A mirror would form a virtual image or a image in the middle of the eye, which would
not be detected by the retinaās rods and cones, or the cameraās charge-coupled device.
Keeping the shutter open for a long time allows more light to enter the camera. More light entering the camera forms a brighter image in dim conditions.
The iris in an eye is a muscle that makes the pupil hole of the eye open and close. The iris is similar to an aperture motor in a camera, which makes the aperture hole open and close.