# © UNT in partnership with TEA - AAVTC: Commercial Photography Practicum – Math in Photography Math in Photography AAVTC: Commercial Photography – Shutter.

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UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Math in Photography AAVTC: Commercial Photography Shutter Speed UNT in partnership with TEA Copyright Texas Education Agency, 2015. All rights reserved. Slide 2 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Math in Photography Math abounds in photography in ways that make it seem easy. o Without thinking, a photographer will think in terms of complex mathematical equations as they adjust their aperture, ISO, and shutter speed. An important, but lesser known mathematical relationship in photography is with focal lengths. Copyright Texas Education Agency, 2015. All rights reserved. Slide 3 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography What Focal Length Isnt The last time we spoke about focal length in-depth was when we discussed lenses. Many people just associate focal length as being how zoomed in a particular lens is. While it is true that the higher the millimeters of a lens, the more telephoto the lens is considered, the actual definition of focal length measures something else. Copyright Texas Education Agency, 2015. All rights reserved. Slide 4 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography What is focal length? Focal length is the distance in millimeters from the optical center of a lens to the sensor at the back of the camera. Photo from the public domain. Copyright Texas Education Agency, 2015. All rights reserved. Slide 5 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography 35mm Equivalent You may have come across the term "35mm equivalent" when looking at focal length before. This term is based upon old film cameras that used 35mm film. The term exists to describe the field of view with a lens through cameras that have different sensor sizes. Copyright Texas Education Agency, 2015. All rights reserved. Slide 6 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Example It used to be that no matter what camera you put it on, a 28mm lens would give you the same field of view. However, with the advent of digital cameras, there is no universal relationship between the focal length of a lens and the angle of view that is received. Since the size of a cameras sensor determines the angle of view, a 28mm lens on a film camera would not produce the same image as a 28mm lens on a small digital camera. Copyright Texas Education Agency, 2015. All rights reserved. Slide 7 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Cameras with Different Sensor Sizes The camera on the right has full frame sensor, while the camera on the left has a cropped sensor. Photo from the public domain. Copyright Texas Education Agency, 2015. All rights reserved. Slide 8 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Different Sensor Sizes Sensors come in all different shapes and sizes. The size and shape of a cameras sensor determines the aspect ratio of the photos it produces. For example, most medium or large format cameras have a square sensor and produce images with a square aspect ratio because they have a square shaped sensor. Copyright Texas Education Agency, 2015. All rights reserved. Slide 9 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Cropped vs. Full Frame Most modern day camera sensors fall into two categories: o Full Frame Cameras o Cropped Sensor Cameras Copyright Texas Education Agency, 2015. All rights reserved. Slide 10 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Full Frame Sensor Full Frame Sensor Full frame sensors are the same size and shape as 35mm film. Therefore, a lens with a focal length of 50mm would look the same on both an old film camera and a modern day DSLR with a full frame sensor. Its focal length is 50mm no matter what. Copyright Texas Education Agency, 2015. All rights reserved. Slide 11 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Cropped Sensor Cropped Sensor A cropped sensor is a sensor that produces images that are a different shape than a 35mm film. It is almost as though the sensor has been cropped, or had a portion of it cut off. For this reason, the field of view is smaller than a full frame camera. Copyright Texas Education Agency, 2015. All rights reserved. Slide 12 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Field of View In the image on the right, you can see that the red sensor sees a larger portion of the image than the blue sensor, even though they both have the same focal length. Photo from the public domain. Copyright Texas Education Agency, 2015. All rights reserved. Slide 13 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Field of View The red rectangle is a full frame camera, which has a larger sensor and therefore sees more of the image than the blue, cropped sensor camera. It has a wider field of view. Photo from the public domain. Copyright Texas Education Agency, 2015. All rights reserved. Slide 14 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Buying a Lens Most lens sizes are named according to what they are on a full frame camera. For example, a 50mm lens would have a focal length of 50mm on a full frame camera, but not on a cropped sensor camera. Keep in mind what type of sensor you have when purchasing a lens so you know what the true focal length will be. Copyright Texas Education Agency, 2015. All rights reserved. Slide 15 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Crop Factor Crop Factor measures how far a cropped sensor is from a full frame sensor. Most cropped sensors have a crop factor of either 1.6 or 1.5. Mirrorless cameras have a crop factor of 2. o This means that a 40mm lens would actually have a focal length of 80mm on a mirrorless camera. Copyright Texas Education Agency, 2015. All rights reserved. Slide 16 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Other Ways Photography Deals with Math Equivalent focal lengths are just one of the many ways that photography deals with math. Many of the other ways are like second nature to seasoned photographers, such as yourselves. o A photographer will adjust aperture, ISO, and shutter speed while keeping in mind the inverse relationship that exists between them and light. o The seasoned photographer will also keep in mind their depth of field and how their aperture, focal length, and distance from subject affect the photograph. Copyright Texas Education Agency, 2015. All rights reserved. Slide 17 UNT in partnership with TEA - AAVTC: Commercial Photography Practicum Math in Photography Review Focal length is often different, depending on the size of your sensor. Sensors that are the size and shape of 35mm film are called full frame sensors. Sensors that are smaller than 35mm film are called cropped sensors. Different sensors have different crop factors. Copyright Texas Education Agency, 2015. All rights reserved.