Chapter Six Digital Photography Foundations(How to use the various settings on your digital camera)
Image Size • Large, medium, small, etc. • Choose whatever the largest image size gives you • the most flexibility (enlarging, cropping, high-quality printing, etc.) • Drawback: large image sizes mean less taking images on the same memory card • Comment: memory cards are getting cheaper all the time; get a spare one if necessary
Compression: JPEG • JPEG compression is lossy • The less compression, the higher the image quality • The higher compression, the smaller the image file size • Many digital cameras allow you to set the levels of compression • RAW file format has no compression
ISO setting • Typical settings: 50,100, 200, 400, 800, 1600, 3200 • Auto ISO: the camera chooses an ISO value depending on lighting conditions, e.g. well-lighted scenes 100-200, dark scenes 800-1600 • High ISO settings (e.g. 1600 or above) tend to cause noise in images
ISO setting tips • For well-lighted “normal” shots, use 100-200 for best image quality • For “action” shots, use 400 or 800 for faster shutter speed • For indoor or night shots without flash, use 1600 or above
Color Temperature • Light sources • 2000K Sunrise • 2500K Light bulbs • 5000-5500K Daylight, flash • 9000K Overcast sky • Lower color temperature means “warmer” color (reddish) • Higher color temperature means “cooler” color (bluish)
White Balance (WB) • A piece of white paper would look pure white under broad day light. • A piece of white paper would look a little bit blue under fluorescent light. • We would “see” a white paper in both cases because our brains (not our eyes) already “adjust” the color in real time. • An image sensor would “honestly” record the slightly blue color in the second case. • It is up to the camera’s CPU to “adjust” the color of the image to compensate for the non-white light source. • http://www.photoxels.com/tutorial_white-balance.html
Auto White Balance (AWB) • The camera evaluates the scene and tries to determine the white point(s) of the scene. • Not always successful, e.g. when bright colors fill most of the scene, or in low temperature lighting.
Presets and custom WB • Daylight, cloudy, tungsten, fluorescent, flash, etc. • Best to take test shots to determine the most appropriate presets. • Most digital cameras allow you to manually set a custom WB for a particular lighting condition by taking a shot of a white subject under that condition. • Some digital cameras even allow you to set WB in terms of color temperature, e.g. 5000K
Sharpening • Most digital cameras use in-camera sharpening to compensate for color interpolation. • In-camera sharpening of images may not give the most desirable results as sharpening could remove useful details of an image. • Some cameras allow you to set different levels of sharpening or even disable sharpening.
Color Spaces • A color space determines how many different colors can be recorded on a digital camera. • The most commonly used color space: sRGB • Some digital cameras provide other color spaces which are usually richer than sRGB, e.g. Adobe RGB
Exposure • Correct exposure depends on: • Amount of light hits the sensor (aperture) • Exposure time (shutter) • Sensitivity of the sensor (ISO) • Most digital cameras have good built-in exposure meters to help set the correct combinations of the above.
Aperture • Eg. f2, f2.8, f4, f5.6, f8, f11, f16, f22, etc. • f-stop = Focal length / diameter of aperture • The bigger the aperture, the more light passing through • Aperture affects depth of field • Tutorials on depth of field: http://smad.jmu.edu/dof/ www.photoxels.com/tutorial_dof.html
Shutter speed • 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, … • Longer exposure allows more light to hit the sensor.
Reciprocity • Increasing the shutter speed (freezes movement) can be compensated by widening the aperture (less depth of field). • Similarly, decreasing the shutter speed can be compensated by reducing the aperture (more depth of field).
Full Auto Mode • Fully automatic • Evaluates lighting • Select ISO, white balance, aperture, shutter speed, flash, etc.
Program Mode • Similar to Auto mode • Allow setting ISO, WB, exposure compensation • Allow choosing aperture-shutter reciprocal combinations.
Program Exposure Canon Powershot G6 Very similar to AUTO exposure but you have access to all the normal manual controls, can set the ISO, exposure compensation, use AE lock, bracketing etc. The G6 has program shift, activate shift by pressing the * (AE/FE-Lock) button, then turn the main dial to select from various equivalent exposures. Example (pressing * metered 1/50 sec, F4.0): • 1/30 sec, F4.5 (turn left) • 1/40 sec, F4.0 (turn left) • 1/50 sec, F4.0 (metered) • 1/60 sec, F3.5 (turn right) • 1/80 sec, F3.2 (turn right)
Aperture Priority Mode • Preset aperture (by you) • Camera adjusts shutter speed based on lighting • Give better control to depth of field (wider aperture for less DOF, and vice-versa). • Tip: for portraits, you may set a wider aperture to “blur” the subject’s background • Tip: for landscape, you may set a smaller aperture to make the whole scene clear
Shutter Priority Mode • Preset shutter speed (by you) • Camera adjusts the aperture based on lighting • Tip: fast shutter speed for capturing motion, also avoid “motion blur” due to hand shake • Tip: slow shutter for “creative” blur
Manual Mode • You may set any combination of aperture and shutter speed and other settings (e.g. ISO). • Useful for night and studio photography
Scene Modes • Portrait • “blur the background” through large aperture and center-weighted metering • Night portrait • Slow shutter speed to “see enough light” of the background and flash for the foreground subject • Landscape • Small aperture for deep depth of field • More sharpening, contrast, and saturation
Scene Modes (cont.) • Night Landscape • Slow shutter speed, no flash • Beach/Snow and Backlight • Compensate for overly bright reflections and backgrounds • Close-Up/Macro • Longest zoom and fast enough shutter speed (to avoid “hand shake” blur)
Scene Modes (cont.) • Sports • Relatively fast shutter speed to freeze actions • Continuous shooting • Black and White/Monochrome • Capture grayscale images • Other modes • E.g. fireworks, pets, food
Metadata (EXIF) • Records of exposure settings (e.g. ISO, aperture, shutter speed, etc.) • Accessible through software
Depth of Field inCompact Digital Cameras • Deeper depth of field is achieved by: • Smaller aperture • Shorter focal length • Greater subject distance • Compact digital cameras tend to have smaller image sensors and lenses with shorter focal lengths • Hence, they tend to give deeper depths of field than compact film cameras.
Exposure Latitudeof Image Sensors • Also called dynamic range • Similar to that of slide films • More susceptible to overexposure • Overexposed areas of an image become “pure white” with no details • Tip: use downward exposure compensation to “save” potentially overexposed details