Lesson #6 - EXPOSURE - Lesson 6-3 Added
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    Buddysmom's Avatar
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    DefaultLesson #6 - EXPOSURE - Lesson 6-3 Added

    REMEMBER - NO POSTS IN THIS THREAD. THIS IS FOR THE LESSONS ONLY.

    We will probably take close to 2 weeks for this lesson. Each day you will have an assignment. It will be more of a hands on the camera type thing. You do not have to post pictures. At the end of the lesson, you will get to post one picture for critique. In this picture, you will show us if you understand how to take well exposed photos in manual mode.

    A "QUESTIONS FOR LESSON 6" thread will be started. This is where you will ask any questions you have about the different lessons and assignments. You may post pictures to show us a specific problem. But, we will not critique the pictures. We'll just answer your questions to the best of our ability.

    You MUST post EXIF data with your pictures. This is the only way we have of telling what you may be doing right or wrong. On the Canon, after you take a picture, if you will view the picture in the LCD, you can use the info button on the left side of the camera to display the EXIF data. With the picture on the LCD screen, press the info button twice. This will bring up the window with all the EXIF data. We will need only three #s:

    ISO
    AV
    SS - please write this as a fraction. EX: 1/800, 1/60

    Sometimes I will post a new part of the lesson every 2 days. This will give you more time to do the assignment, if I feel it's needed.

    MANUAL EXPOSURE LESSON 6-1 FOR DSLR CAMERAS

    In this first lesson in manual exposure, I am going to go over the terminology that you should be familiar with. I’m going to go over the basic manner in which exposure is achieved. I’m going to just do a little each day over 4/5 days. This can be very confusing, if you don’t fully understand how each element affects exposure. I am going to start a “Questions for Lesson #6” thread. PLEASE DO NOT POST QUESTIONS IN THIS THEAD. I AM GOING TO JUST ADD EACH DAY’S LESSON TO THIS LESSON THREAD.

    TERMINOLOGY

    EXPOSURE – The amount of light that reaches the film or sensor. Over exposure means too much light has reached the sensor/film, and under exposure means too little light has reached the sensor/film.

    ISO – this is a measure of the sensitivity of film/sensor to light. It is numbered 100-3200. P&S cameras will usually only use between 100-400 ISO and sometimes 800 ISO. DSLR cameras can go from 50-3200 or greater depending on the complexity of the camera. The more sensitive to light the sensor/film is the higher the number. An ISO of 100 is not as light sensitive as an ISO of 1600.

    SHUTTER SPEED (S or TV) – This is how fast or slow the elements of the camera lens opens and closes. It can go from BULB (shutter open until you close it) to 1/8000 of a second. A shutter speed of 1 second keeps the shutter open longer than a 1/100 of a second shutter speed. These numbers are usually written as fractions of a second or whole seconds. In the viewfinder, the SS of 1/4000 of a second is shown as 4000. So a 4000 SS is FASTER than a 50 SS. The whole seconds will be written in the viewfinder with “ marks. Five seconds would appear as 5”, not as 5. The 5 would represent 1/5 of a second.

    APERTURE (AV) – The aperture of a lens is how far open the lens elements will go when the shutter button is push down. It’s similar to the aperture in a faucet. When you open a faucet just a little, the opening is small and only a little water comes out. When you open a faucet the whole way, the opening is large and a lot of water comes out. It works the same with a camera. The larger the opening in the lens, the more light gets to the sensor/film. The smaller the opening in the lens, the less light gets into the sensor/film. This is where it can get confusing. Small numbers represent a large opening in the lens. Also, a large number represents a small opening in the lens. Therefore, an aperture of 1.8 has a larger opening for light to pass thru than an aperture of 22.

    F STOP – The f/stop represents each increment that a lens will open the aperture. It is written as f/1.8, f/5.6, f/11, f/22, etc. The aperture values of most lenses can be anything from:
    1.0, 1.1, 1.2, 1.4, 1.8, 2.0, 2.2, 2.5, 2.8, 3.2, 3.5, 3.8, 4.0, 4.5, 5.0, 5.6, 6.3, 7.1, 8.0, 9.0, 10, 11, 13, 14, 16, 18, 20, 22, 25,29,32 etc.
    Starting with an f/stop of 1.0, each time you go up an aperture value the light getting to the sensor is doubled. Each lens is different in their starting value. This is the f number that you will find on your lens. The 50 mm f/1.8 lens has its starting AV value of 1.8. This is a large aperture. It will let in a lot of light. This lens is considered a good lens to use in low light conditions. Most will go up to at least 22 and some a lot higher. You have to know what your camera/lens is capable of.

    STOP – Whenever you hear the word STOP when referring to ISO, AV, and SS, it is referring to each increment these properties will advance. ISO stops are 50, 100, 200, 400, 800, 1600 and 3200. Each stop, whether ISO, AV, or SS, increases the light by doubling it or decreases it by halving it. An f/5.6 aperture will let in twice as much light as an f/6.3, and 4 times as much light as f/7.1. Same goes for SS. A SS of 1/2000 will let in half as much light as a SS of 1/1600 and 4 times less light than 1/1250 of a second.

    Now that we are all thoroughly confused, we will relate these terms to exposure.

    Correct exposure is reached when the ISO, AV, and SS are all in balance. Think of ISO as the fulcrum (balancing point) of a see saw. The AV and SS are the ends of the see saw board. What makes exposure hard is that there is not one correct value for an exposure. There are many depending on what values you give the ISO, AV, and SS. You can take two pictures with two totally different sets of values and they’ll both be properly exposed. About the only difference you will see in the picture is the depth of field/DOF.

    Now before we go on with how to set proper exposure, you have to know where to locate and change the ISO, AV, and SS on your camera. I can only speak for the Canon cameras, since this is what I use. You can refer to your manuals to find how to change yours. I do know the Nikon cameras change the values similarly to the Canons except the buttons are in different places.
    The ISO can be changed from the main menu or there’s an ISO button on the back of the camera you can push. It will take you to the ISO settings. Use the up/down arrows to change the ISO and then hit set.
    To change the aperture, locate the aperture (AV) button on the back on the camera on the right side near the LCD. On the Nikon, I believe it’s on the top of the camera. At this point you will push the shutter button half way down and release. This will activate the AV and SS so they can be changed. While holding the AV button turn the shutter wheel. This will change the aperture.
    To change the SS, press the shutter button half way and release. Now you can turn the shutter wheel to change the SS. Unlike the AV, you don’t have to push another button to change the SS. It doesn’t matter which order you change these for now.

    That’s all for today. What I want everyone to do for homework is learn how to change your ISO, AV, and SS in manual. Also, I want you to find the Standard Exposure Index in the viewfinder or on the LCD. On the Canon it looks like this -2| | | | | | |\/| | | | | +2. I want you to watch what happens to the Exposure Level Mark when you change ISO, AV, and SS. On the Nikon, I believe it’s a 0. When you turn the ISO, AV, or SS | | | | appear on either the left or right side of the 0.

    Starting with the next lesson, we will learn how to achieve correct exposure.



    Eiderdowns That's My Buddy
    CDX, RE, WC, CGC, TDInc.
    Monnie

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    DefaultRe: Lesson #6 - EXPOSURE

    MANUAL EXPOSURE LESSON 6-2 FOR dSLR CAMERAS

    So, how do you achieve correct exposure? The best place to start is with the ISO value. If you go outside and it is a bright sunny day with no clouds in the sky, you will want to use an ISO of 100. This is because 100 is a less light sensitive value. The sensor will not be overwhelmed by the light coming in. If the day is bright but cloudy, you could use an ISO of 200. An ISO of 400 or 800 can be used if its very cloudy or getting dark outside or you’re in an area that isn’t letting in much light like in the woods. At night or inside you can use an ISO of 800 or greater. Inside an ISO of 800+ means the sensor/film is very sensitive to light. It will react to just a small amount of light coming into the camera. Just remember that an ISO of 800 or more will produce “noise” on digital pictures. Noise is the graininess that you see as speckles of color in the background of your pictures.
    Now Remember: the SS and AV are sitting on the seesaw above the ISO. They have to remain balanced. If they are out of balance, your shots will be over or under exposed. There really are many ways to achieve balance. This is how I do it. After I’ve chosen my ISO, I decide what aperture I want to use. Am I taking landscape shots? Do I want a shallow DOF? Will my subjects be moving or stationary? Let’s say I want to take pictures of Buddy RUNNING (faster shutter speed) in my field. I’m going to need quite a bit of the picture in focus (broad DOF). Since I need a fast shutter speed, I’m going to have to make sure the aperture lets in as much light as possible without blurring the background too much. I’m going to choose an aperture of f/6.3. This is a medium fast aperture. But it will still let me use a fast shutter speed.
    I dial in an aperture of f/6.3 on the camera. All I have to do now is set my SS. I do this my turning the shutter wheel until the exposure level mark in the view finder is in the middle. If I look at the SS that I dialed in, it should be around 1/650. This is fast enough to get a moving dog. Now just take the picture.
    Let’s say I want to blur the background even more as Buddy moves across my view. How would I do this?
    FOR EVERY STOP OF APERTURE DOWN/UP THAT YOU MOVE, YOU HAVE TO MOVE THE SS THE SAME NUMBER OF STOPS IN THE OPPOSITE DIRECTION TO RETAIN THE SAME EXPOSURE.
    So, I’m going to change my AV to f/4.0. That’s 4 STOPS down from f/6.3. I will be letting in more light. This is a larger aperture. I have to increase the SS 4 STOPS from 1/650 to 1/1600. This 1/1600 SS will let in less light than the 1/650. The exposure level mark should return to the middle with these settings. If you take both these picture, they should look the same exposure wise with only a difference in DOF.
    Check out this chart and practice “taking” pictures. This will give you a better understanding of how the SS and AV affect one another.
    http://www.photonhead.com/simcam/shutteraperture.php


    Remember your aperture is dependant on how much light is available. The more light that is available the larger an f stop you can use. If there is less light available, you have to use a smaller f stop or change your ISO.

    A word about ISO. It is always best to use the lowest ISO value that you can and still achieve the exposure you want with your shot. You will achieve your best and sharpest pictures at a low ISO.

    Here is another good practice site. Practice putting in different AV and SS values and see what happens.
    http://www.photonhead.com/beginners/stops.php

    Today’s assignment is to practice on these two websites. See if this doesn’t give you a better understanding of how ISO, AV, and SS affect exposure.
    Practice taking pictures and changing the AV and SS in exact ratio to one another.





    Eiderdowns That's My Buddy
    CDX, RE, WC, CGC, TDInc.
    Monnie

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    DefaultRe: Lesson #6 - EXPOSURE - Lesson 6-2 Added

    Just wanted to add... some cameras do not have ISO 100. I know the Nikon D50 starts at ISO 200. And I believe the D70 does as well. So you don't have the option to chose ISO 100, but you would use the 200 instead

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    DefaultRe: Lesson #6 - EXPOSURE - Lesson 6-2 Added

    Manual Exposure of dSLR Cameras Lesson 6-3

    Today we are going to learn about the limitations of the auto exposure function on digital cameras. I’ve left this till now because you have to know how to use the manual mode of your camera properly before you will understand how to second guess it.
    Before I go on, you have to know how the camera goes about accessing exposure. Years ago before there were auto exposure cameras you had to use a gadget called a light meter. It was a small gadget with lots of dials and numbers on it. I never did figure out how my dad used ours. You held the light meter in the light where your picture was to be taken. It measured the actual lighting of the surrounding area and gave you the correct aperture and shutter speed. You then set them into your camera. This was a very precise way to expose a photo. Auto exposure measures REFLECTED light. The sensor reads the light reflected off the exposure points. There are several ways to read this measure that you can choose.

    Evaluative – There are as many as nine points that the camera “reads” to get the correct exposure
    Partial – Measure an area slightly larger than the middle area of the shot for exposure.
    Center weighted – Measure light at the center and then average for the entire shot. It gives most weight to the center.
    Spot – Uses only the very center of the frame for exposure.

    This metering can throw off the cameras sensors if the light isn’t distributed just right. If you have a dark subject and all the surrounding area is lighter or vice-a-versa, using the cameras auto exposure may result in an incorrectly exposed shot. To obtain correct results you can bracket your shots either manually or automatically. To bracket a shot is to take a picture at the setting the camera tells you on your exposure level indicator. Then you take 2 other pictures of the same scene, one a stop higher and one a stop lower than the camera indicates. Most dSLRs have the ability to do this automatically in the AEB (automatic exposure bracketing) function of the camera. If you know you want your subject exposed properly, I would use either the partial or spot metering mode. If you’re doing a landscape or sports, I would use evaluative or center weighted.

    So how can you tell right away if you have decent exposure on a picture? Both Canon and Nikon cameras will display a histogram of the photo on the info screen. The histogram is a diagram of where the pixels fall between light and dark within a picture. The histogram goes from 0-255, when 0 represents black and 255 represents white. Everything else fall somewhere between. If your photo is over exposed too many of the pixels will fall on the right side of the graph. If your photo is under exposed too many pixels will fall on the left hand side of the graph. You want the pixels spread out evenly toward the sides. It doesn’t matter how high the peaks are as long as they don’t touch the edge. Also any blown out areas in your picture will blink black off and on. You can find the histogram by displaying a picture on the LCD screen and, on Canon cameras, pushing the info button twice. This will bring up a screen with your exposure info and the histogram. On Nikon cameras, bring up the picture of the LCD screen and use the arrows to scroll to the histogram. You have to remember, though, that there are no “bad” histograms. A picture that was meant to be very dark or very light all over may be perfectly exposed with all the pixels on one end or the other of the histogram. Just make sure the pixels are right up touching the edge. They should drop off just before or right at the edge. They should not go up the edge of the graph.
    Here is an excellent article on the use of histograms: http://www.luminous-landscape.com/tu...tograms.shtml#
    Make histograms your friend.
    I hope I’ve explained this so you can get some understanding about why your photo may still be over exposed or under exposed even though the camera says they were properly exposed. By using the histogram to check for exposure, you can re-shoot the picture using different values if needed.

    Your assignment is to adjust your camera using the exposure level indicator, take a picture, and check it with the histogram to check exposure.


    Eiderdowns That's My Buddy
    CDX, RE, WC, CGC, TDInc.
    Monnie

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