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Micah Murdock The Basics of Photography and Exposure
Definition – Exposure is the total amount of light that passes through the lens and onto the medium of a camera. It is responsible for determining many of the characteristics of an image. The following slides give examples of some of the most important elements of controlling an image’s exposure After viewing each group of slides, a brief description of the element is given as well as its effect on the photo. After the four examples, we will then break each element down individually. Finally we will give you a chance to critique several photos on your own based on the information covered in this tutorial.
First lets find out what we already know about exposure. Here is an example of an image many would consider well exposed. Using what you already know, what are some of the reasons this could be considered true? Write your answer on the handout provided
The colors are bright and vivid There is good contrast between the bright and dark portions of the image. The main subject is in focus while the background is less so. This provides additional interest for the viewer The butterfly seems to be stopped in mid motion Here are some of the reasons this image could be considered well exposed. Now Lets learn a little more about exposure and how these characteristics of the image can be achieved
Example 1 First its important to understand that there is no such thing as a single set of rules for “correct exposure” however there are several mechanisms of a camera that must be correctly understood and manipulated to properly achieve the desired exposure. Click on the buttons below to see two examples of different exposures of the same subject What do you think the photographer did right or wrong in regard to the exposure of these two photographs? Write your answer on your handout Example 2
The 4 Elements of Exposure When taking a picture of someone or something, there are many elements that combine to determine the quality of that picture. One of the most significant elements is the exposure. We will start first by developing a better understanding of how four specific variables effect the exposure and how they play a part in creating a beautiful image under a variety of lighting situations. They are: 1.Aperture 2.Shutter Speed 3.ISO 4.White Balance Lets take a look at each on of these individually
Identifying the Elements of Correct Exposure The Effects of Aperture Although the overall exposure between the two pictures of this gumball machine looks the same, there is one major difference between them – The picture on the top has a much larger aperture. This impacts the picture in the following ways When the aperture is small it means the opening of the camera is small, therefore it takes a longer time for the same amount of light to correctly expose the image (the larger the f stop the smaller the aperture). The background in the picture on the top is blurry compared to the one on the bottom. This is referred to as a shallow depth of field. A large aperture (the picture on the top) creates a more shallow depth of field. In this case the photo’s both look correctly exposed because I compensated for the larger aperture by slowing down the shutter speed Aperture: f 5.6 Shutter Speed: 1/16 ISO: 100 White Balance: Auto Aperture: f 25 Shutter Speed: 1.3 sec ISO: 100 White Balance: Auto
Identifying the Elements of Correct Exposure The Effects of Shutter Speed In this example the picture on the top has the correct shutter speed for a correct exposure, showing all the color and detail of the plant. With all else remaining constant, the picture on the bottom has a “faster shutter speed”. This results in a picture which is under exposed. To compensate for this we could slow down the shutter speed or decrease the aperture. However, remember if we decreased the aperture, it would also effect our depth of field. Aperture: f/13 Shutter Speed: 1/40 sec ISO: 100 White Balance: Auto Aperture: f/13 Shutter Speed: 1/250 sec ISO: 100 White Balance: Auto
Identifying the Elements of Correct Exposure The Effects of ISO In this example, all things remaining equal, we see that the picture on the bottom is severely underexposed. However this is not due to either shutter speed or aperture. The ISO setting on your digital camera determines the sensitivity of your camera to light. In this case you can see the ISO of the picture on the top was set to the maximum while the one on the bottom is at the minimum. Adjusting the ISO is easy enough but there can be a price paid in the quality of the picture that we will cover later in the tutorial Aperture: f 5.0 Shutter Speed: 1/10 sec ISO: 1600 White Balance: Auto Aperture: f 5.0 Shutter Speed: 1/10 sec ISO: 100 White Balance: Auto
Identifying the Elements of Correct Exposure The Effects of White Balance The color white can change dramatically depending in large measure by the color of the light illuminating it. Here we see a good example of this variation. In order to compensate for this variation most digital cameras have a white balance setting. In this case we see a white phone that changes color 4 times as a result of 4 different settings. The only factor that truly changed was the way I told the camera to “see” the white. Here are the settings for all 4 photos These pictures were taken in a room lit mostly by natural sunlight so the first picture (auto) and fourth picture (daylight) are the most correctly exposed. Here are the white balance settings used for each photo Top left – Auto Bottom left - Tungsten Top right – Fluorescent Bottom Right – Natural Light All other settings Aperture – f 5.0 Shutter speed – 1/12 sec ISO – 400
Lesson #1 –The 4 Elements of Exposure defined Lesson #2 – Aperture: Opening our eyes and our lens Lesson #3 – Shutters and the speed of light Lesson #4 – ISO You being sensitive Lesson #5 – White Balance: No discrimination here Examples and practice Lesson Modules for The basics of Exposure Click on each of the links below for information and examples of the four elements of exposure.
Exposure Defined Aperture Shutter Speed ISO White Balance The opening in the lens that allows light to enter the camera The mechanism in the camera that controls the amount of light allowed to reach the camera’s sensor/film A measurement of the relative light sensitivity of the camera’s sensor The color of the light source as it will appear in the picture relative to pure white. First write down what you think each of these terms mean and then click on them to check your answers Lesson #1
Lesson #2 Aperture Aperture has two basic effects on the image 1.The aperture setting controls the amount of light that is able to strike the medium (sensor/film) by restricting or enlarging the size of an opening in front of the medium 2.The aperture also has an impact of what is called the depth of field in you photo. The depth of field is the range of distance in which the subject being photographed is focused sharply. In the photo to the right the green car is less focused than the red car therefore this photo is using a more shallow depth of field. In general the smaller the aperture the more shallow is your depth of field
Lesson #3 Shutter Speed Shutter Speed adjust the speed at which the shutter exposes the sensor. It can be adjusted to manipulate the amount of time that light is allowed to reach the sensor/film. In the example above a fast shutter speed was used to create a stop action effect. The medium was only exposed to the image for a very brief amount of time allowing the photographer to catch the movement of the surfer in a clear and focused moment, seemingly stopping him in mid air In the example on the right the shutter was left open for a longer amount of time allowing the movement of the train to blur as it moved. This can be used to create a feeling of motion or time
Lesson #4 ISO Remember ISO is the setting that adjusts the camera’s sensitivity to light. In film cameras this was determined exclusively by the film being used. If you wanted to change the ISO of your pictures you would have to change your film. Luckily in digital cameras today, the ISO can be changed with a simple adjustment of the setting on your camera. The main reason one would adjust the ISO is to increase the camera’s ability to properly expose a photo in low light situations. A draw back to this is the effect it has on the quality of the image. Increasing the ISO too high can create “noise” or grain in your photo. This also makes picture more difficult to enlarge as this will only emphasize the grainy look As seen in this extreme example, this picture was taken in very low light conditions and a very high ISO was used. As a result a large amount of noise was introduced, reducing the quality of the image significantly.
Lesson #5 White Balance Believe it or not there are many shades of white. At least that is how your camera will see it. Below is a powerful example of how many shades of white there are. Adjusting your white balance can help your exposure to reflect the mood or feel of your picture in many ways.
Now that you have been given the specifics on the four elements of exposure lets do some practice. In the following slides you will be presented a series of photographs. Read the scenario and then either suggest what setting adjustments would improve the exposure, or determine which setting could have been used to create the effect shown. First read the description of what the photographer did or was trying to do, then write your answers on the handout provided. Once you have written your answers, you can check them by clicking on the button to view the answers. Examples and Practice
Example #1 This picture was taken in the middle of the day with plenty of sunshine and gives a good example of a “stop motion” technique. What exposure settings would you use to replicate this picture and eliminate blurring when the subject is moving quickly? Check Answer Suggested Answer With lots of light in the middle of the day the stop action technique is not hard to achieve, just increase your shutter speed to something above 1/250 sec. Adjust the ISO to the lowest possible setting (around 100). This allows the quality of the picture to be as high as possible. Aperture may need to be slightly larger than normal to compensate for the fast shutter speed. White balance can almost always be left on auto when outdoors.
Example #2 Jill has a vase of flowers on her nightstand. She wants to take a picture of them before they die so she will never forget the wonderful way in which her husband surprised her. She would love to frame this picture to a 16x20 poster size but is frustrated with her poor exposure. What adjustments could she make to correct the exposure and show all the pretty colors of her flowers? Check Answer Suggested Answers Jill could move her vase of flowers to a place where there is more light She could slow down the shutter speed to allow the camera’s sensor more time to pick up more light however she may need a tripod to ensure she doesn’t take a blurry picture She could increase the aperture allowing more light to come through the lenses. This would reduce her depth of field leaving some of the flowers at the back of the vase more out of focus (this may or may not be a desired effect). It would not be a good ideas to increase the ISO as this would reduce the quality of her photo and thwart her plans to enlarge and frame the picture
Example #3 Check Answer While I was hiking I came across this beautiful stream and wanted to capture the flowing water in a way that gave life to the motion of the stream. When I looked at my picture I was thrilled to see that, while the branches that framed my photo were clear and sharply focused, I was able to show this soft silky effect on the waves of the water. What settings would you use to achieve this? (Hint you will need a tripod). Suggested Answer Put your ISO on the lowest available setting (normally 100). Aperture should be set high to allow the depth of field to keep both the river and the branches in focus. Slow your shutter speed WAY down. (This is where the tripod comes in). I would recommend taking several shots at 1,5, and 10 sec. Its hard to tell which setting will give you the best results as all streams flow differently. White Balance would remain on Auto
Example #4 Check Answer I was trying to take a stunning picture of this beautiful sunset scene. I wanted to ensure I could see the mountains and the green field but I found that if I exposed the sun correctly the fore ground was too dark but if I exposed the foreground correctly the sun was overexposed. What can I do here? Suggested Answer This is a very tricky scenario. Because of the problem described above. One thing many photographers will do is make a choice. Which do I want to see more, the beautiful red sky or the way it effects the foreground, and then sacrifice one or the other. Another consideration for this picture could have been to wait until the sun was completely behind the mountain. This reduces the chance of overexposing significantly. Last you could adjust your white balance to a cloudy or shady preset (if available). This helps you camera expose the sunlight more accurately
Congratulations You have finished the exposure tutorial. If you have any additional questions you may click on the buttons below and review the material again. Great job and may you always have great light. The 4 elements of exposure The 4 elements of exposure Lesson Modules Lesson Modules Home
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