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Depth Of Field Demo
- 1. 3/14/2009 Depth of field demo ©2009 Len Cook Basic scene Depth of field is the range of acceptable sharpness in a photograph of a scene. h i ht hf Depth of field changes when the photographer changes aperture. Depth of field is greater when the photographer uses small apertures. uses small apertures Depth of field is less when the photographer uses large apertures. 1
- 2. 3/14/2009 Basic scene • Changes in depth of field are easiest to see when these items are in use: these items are in use: A camera – A lens – An object or person that is the subject – An object or person closer to the camera than the – subject, but still in the picture. – An object or person farther from the camera than the subject, but still in the picture. – Enough light to shoot a photo at f/22 Basic scene Example: Item farther Item closer Item closer Subject than the than the subject from subject to the Camera Lens the camera camera 2
- 3. 3/14/2009 View through the camera • Focus on the subject at f/2.8 in this example. f/2.8 is the largest aperture on the lens in this example. Viewing aperture • All modern cameras keep the lens aperture fully open for focusing. fully open for focusing • The diaphragm stops down to the working aperture ONLY during the exposure while the shutter is open. • SOME cameras have a depth‐of‐field preview. • DOF preview allows the photographer to view through the lens at the aperture the photo will use. 3
- 4. 3/14/2009 Set the aperture to f/2.8 • Take a picture and it will look like this: Item closer Item farther than the than the subject to the subject from camera is out the camera is of focus. out of focus. You must use a shutter speed appropriate to f/2.8! Take the picture NOW. Change the aperture • Now you must change the aperture to the smallest available aperture on your camera/lens smallest available aperture on your camera/lens combination, f/22 in this example. • You must also change the shutter speed. • Because you are going from f/2.8 to f/22 you will reduce the light hitting the film or sensor by 6 stops. That is a very big reduction. • You must increase the exposure time by 6 stops. That is a very big increase. 4
- 5. 3/14/2009 View the scene again • Focus on the SAME SUBJECT! Keep the camera at the same distance as the first picture. Focus on the same subject as the first picture. View through the camera • Focus on the subject, aperture at f/22. Even with the aperture set at f/22, the view looks the same as it did at f/2.8. 5
- 6. 3/14/2009 Full aperture viewing • You changed the aperture to f/22 but the view through the camera looks the same. th h th l k th • All modern cameras keep the lens aperture fully open for focusing. • The diaphragm stops down to the working aperture ONLY during the exposure while the aperture ONLY during the exposure while the shutter is open. Depth‐of‐field preview • SOME cameras have a depth‐of‐field preview. • DOF preview allows the photographer to view through the lens at the aperture the photo will use. • Sometimes DOF preview is a button. Sometimes it is a lever. Sometimes it is a lever • DOF preview control (button or lever) may be on the lens or may be on the camera. 6
- 7. 3/14/2009 Preview depth‐of‐field • If you have it, use it and the viewfinder will look like this: DOF preview may make the viewfinder VERY dark if a small aperture is set. Depth‐of‐field greatly expanded • Take a picture at f/22 and it will look like this: Item closer Item farther than the than the subject to the subject from camera is the camera is much sharper. much sharper. You must use a shutter speed appropriate to f/22! 7
- 8. 3/14/2009 Now you try it • Repeat this process with subjects of your own. • Try different subjects. • The three items or persons in the photo can be different. They do not have to be three of the same thing, like juice cans. 8