What Happens When I Take a Picture?
The same thing that happens when you close your eyes, open them for a split second, and close them again.
Light is reflected or transmitted by the subject. When your eyes are open (shutter), the light passes through the cornea (lens), adjusted for brightness by your iris (aperture), onto your retina (film or sensor), and decoded by your brain into an image you can understand (Development, or digital image creation).
The adjustments to the picture taking process include:
Shutter Speed
Aperture
Focus
ISO (Film Speed)
White Balance (Color)
A brief description of the effect of these settings follows.
Shutter Speed
The shutter speed, or the length of time light will strike the sensor or film, is measured in seconds. Typical exposures will be in fractions of a second between 1/30th and 1/8000th. The shutter speed setting does 2 things:
1. It regulates the amount of light that hits the sensor or film.
2. It regulates the sharpness of the subject if the subject and/or camera move during the exposure.
Aperture
Aperture is the diameter of the lens opening, relative to the focal length. Aperture is expressed as 'f' (focal length) divided by (/) value. Typical aperture settings include f/1, f/1.2, f/1.4, f/2, f/2.8 , f/4, f/5.6, f/8, f/16. The larger the value, the SMALLER the hole is. Aperture does 3 things:
1. It regulates the amount of light that hits the sensor or film.
2. It determines the depth of field. (what range of distances are in focus. A smaller hole mean the focus area is deeper.)
3. It determines the overall sharpness of the image. Most lenses are sharpest between f/5.6 and f/11.
You will notice that item 1 for shutter speed is the same as item 1 for aperture. Think of it as a water faucet. How much you open the faucet is aperture. How long you leave it open is shutter speed. They both contribute to the amount of water that ends up in the bucket. In a camera, they both contribute to the amount of light that hits the sensor or film.
Focus
Focus is usually achieved by moving the lens elements closer to, or away from the sensor or film. The light must converge exactly on the film or sensor to be sharp.
ISO
This is an abbreviation for "International Standards Association". You may have also seen film speed called "ASA" which stands for "American Standards Association". The abbreviations refer to the sensitivity of the film or sensor to light. The higher the rating, the more sensitive the film or sensor will be. ISO determines 3 things:
1. The amount of light it takes to properly expose the film or sensor.
2. The grain size (in film) or sensor noise (digital) that is apparent on the image.
3. The color accuracy (particularly in digital).
If the silver particles in film are made larger, they are more sensitive to light. However, smaller silver flakes provide for sharper, more detailed prints. Digital has entirely different issues, but the result is similar. With a digital camera, sensitivity is increased by amplifying to light signals electronically. Just like turning up the volume on a stereo introduces background noise and distortion, so does a digital sensor. Colors become muted, background noise becomes registered as light in the image, and the sensor has a tough time picking the light out of the noise.
Digital camera sensors have what is called a "base ISO". This is the default sensitivity with no amplification applied. When the camera is set to this ISO, the result is almost always the best quality the sensor can produce. You may need to use a higher ISO if there is not enough light to record the image properly.
A film obviously cannot be adjusted from it's base ISO, but development times can be varied to achieve this effect.
White Balance
White balance, like ISO is adjustable on a digital camera, and fixed on a film camera. Film is corrected for proper color balance when the image is printed. In a digital camera, the color balance needs to be set before the image is made.
Light is measured in photography on 2 axis. Temperature, and tint. Temperature is a scale from warm to cool, yellow to blue. It is often measured numerically in kelvin. Tint is the scale from green to magenta. The human brain automatically adjusts white balance by assuming the lightest object in view is white. For this reason, we get away with fluorescent lighting, (green and red alternating at 60hz), tungsten, (very warm or yellow light), sodium vapor, (orange), and our brains adjust. Film and digital sensors record the light as it is. For this reason the adjustment must be manually done by selecting film designed for specific light, or compensating in the camera for digital.
Now, to combine these settings to get a good photograph!
[to be continued...]
The same thing that happens when you close your eyes, open them for a split second, and close them again.
Light is reflected or transmitted by the subject. When your eyes are open (shutter), the light passes through the cornea (lens), adjusted for brightness by your iris (aperture), onto your retina (film or sensor), and decoded by your brain into an image you can understand (Development, or digital image creation).
The adjustments to the picture taking process include:
Shutter Speed
Aperture
Focus
ISO (Film Speed)
White Balance (Color)
A brief description of the effect of these settings follows.
Shutter Speed
The shutter speed, or the length of time light will strike the sensor or film, is measured in seconds. Typical exposures will be in fractions of a second between 1/30th and 1/8000th. The shutter speed setting does 2 things:
1. It regulates the amount of light that hits the sensor or film.
2. It regulates the sharpness of the subject if the subject and/or camera move during the exposure.
Aperture
Aperture is the diameter of the lens opening, relative to the focal length. Aperture is expressed as 'f' (focal length) divided by (/) value. Typical aperture settings include f/1, f/1.2, f/1.4, f/2, f/2.8 , f/4, f/5.6, f/8, f/16. The larger the value, the SMALLER the hole is. Aperture does 3 things:
1. It regulates the amount of light that hits the sensor or film.
2. It determines the depth of field. (what range of distances are in focus. A smaller hole mean the focus area is deeper.)
3. It determines the overall sharpness of the image. Most lenses are sharpest between f/5.6 and f/11.
You will notice that item 1 for shutter speed is the same as item 1 for aperture. Think of it as a water faucet. How much you open the faucet is aperture. How long you leave it open is shutter speed. They both contribute to the amount of water that ends up in the bucket. In a camera, they both contribute to the amount of light that hits the sensor or film.
Focus
Focus is usually achieved by moving the lens elements closer to, or away from the sensor or film. The light must converge exactly on the film or sensor to be sharp.
ISO
This is an abbreviation for "International Standards Association". You may have also seen film speed called "ASA" which stands for "American Standards Association". The abbreviations refer to the sensitivity of the film or sensor to light. The higher the rating, the more sensitive the film or sensor will be. ISO determines 3 things:
1. The amount of light it takes to properly expose the film or sensor.
2. The grain size (in film) or sensor noise (digital) that is apparent on the image.
3. The color accuracy (particularly in digital).
If the silver particles in film are made larger, they are more sensitive to light. However, smaller silver flakes provide for sharper, more detailed prints. Digital has entirely different issues, but the result is similar. With a digital camera, sensitivity is increased by amplifying to light signals electronically. Just like turning up the volume on a stereo introduces background noise and distortion, so does a digital sensor. Colors become muted, background noise becomes registered as light in the image, and the sensor has a tough time picking the light out of the noise.
Digital camera sensors have what is called a "base ISO". This is the default sensitivity with no amplification applied. When the camera is set to this ISO, the result is almost always the best quality the sensor can produce. You may need to use a higher ISO if there is not enough light to record the image properly.
A film obviously cannot be adjusted from it's base ISO, but development times can be varied to achieve this effect.
White Balance
White balance, like ISO is adjustable on a digital camera, and fixed on a film camera. Film is corrected for proper color balance when the image is printed. In a digital camera, the color balance needs to be set before the image is made.
Light is measured in photography on 2 axis. Temperature, and tint. Temperature is a scale from warm to cool, yellow to blue. It is often measured numerically in kelvin. Tint is the scale from green to magenta. The human brain automatically adjusts white balance by assuming the lightest object in view is white. For this reason, we get away with fluorescent lighting, (green and red alternating at 60hz), tungsten, (very warm or yellow light), sodium vapor, (orange), and our brains adjust. Film and digital sensors record the light as it is. For this reason the adjustment must be manually done by selecting film designed for specific light, or compensating in the camera for digital.
Now, to combine these settings to get a good photograph!
[to be continued...]
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