ISO meets Aperture and Shutter Speed How to sort out the exposure trifecta and capture the exposure you want.

Transcription

1 Before and After the Click Training ISO meets Aperture and Shutter Speed How to sort out the exposure trifecta and capture the exposure you want. Warning: This tutorial requires decision making. Created by: Winston C. Hall Tuner Photography 114

2 The Exposure Trifecta - ISO, Aperture and Shutter Speed ISO determines how sensitive the sensor is to light. ISO = S for sensitivity. Aperture is the size of the lens opening. Aperture = I for intensity. Shutter Speed is the length of time the shutter remains open. Shutter speed = T for time. ISO, Aperture and Shutter Speed combined determines the total exposure. Exposure = E Here s the equation for total exposure S + I + T = E. This means there are three variables that can be adjusted to alter the total exposure. Set the Since ISO sets the sensitivity of the sensor, aperture determines the quantity of light that is allowed to past through the lens and shutter speed sets the effective length of time the shutter remains open, the total exposure is then proportional to ISO plus aperture plus shutter speed. What is a total exposure? It s determining the correct amount of light that must strike the sensor to create a properly exposed image. ISO, Aperture and Shutter Speed settings are measured in units referred to as a stop. When shutter speed, aperture or ISO is changed one full stop it changes the unit by either doubling or halving the amount. A change in shutter speed from 1/500 sec to 1/1000 is a one- stop change which results in the shutter speed being doubled. A change in shutter speed from 1/4000 sec to 1/2000 is a one- stop change that halves the shutter speed. Shutter speed, aperture and ISO can also be adjusted by either half or third stops. Most Nikon cameras have a timed shutter speed range from 30 seconds to 1/8000 second. Shutter speeds that are displayed with a quotation ( ) mark indicate seconds (2 = two- seconds). All other shutter speeds are a fraction of a second (125 sec = 1/125 sec). For shutter speeds slower than 30, the Bulb setting in Manual Exposure mode must be selected. Selecting the correct camera settings How do you go about selecting the correct setting for shutter speed or aperture? One option is to set the ISO setting based upon the intensity of the light source, then use the Programmed Auto, Aperture Priority Auto or Shutter Priority Auto exposure modes. Select one of the three exposure modes, set the ISO, select the Aperture or Shutter Speed you want to use and let the camera software program select the other variable for you. At the beginning of a photo session, photographers should ask themselves what do I want to control, aperture or shutter speed? Then select the appropriate exposure mode. For example, if you want to control the aperture setting, select Aperture Priority Auto exposure mode, set the ISO and select the desired aperture, point the lens at the scene so the light meter can measure the intensity of the light and let the camera select the appropriate shutter speed. To control the brightness of the exposure use the Exposure Compensation feature. Another option is to select Manual Exposure Mode, set the ISO, select the variable you want to control (shutter speed or aperture), point the camera at the scene, read the analog exposure scale and then adjust the other variable (shutter speed or aperture) until you ve achieved the desired exposure value. Note: when using Manual Exposure mode, the Exposure Compensation feature does not impact image brightness. 2

3 Relationship between Shutter Speed and Aperture Settings Shutter Speed 1/8 1/15 1/30 1/60 1/125 1/250 1/500 1/1000 1/2000 1/4000 1/8000 Aperture f/32 f/22 f/16 f/11 f/8 f/5.6 f/4 f/2.8 f/2 f/1.4 f/1 Note: The above shutter speed and aperture relationship is theoretical for one light source, not a guide for all lighting situations. The relationship shows the impact of a one- stop change on the other variable to create an equivalent exposure. Factors that affect ISO, Aperture and Shutter Speed selections: What are the factors that affect ISO choice? Desired image quality Visibility of noise and grain Intensity of the light source Desired depth of field or shutter speed What are the factors that affect aperture choice? ISO sensitivity setting Desired Depth of Field Hyper- focal settings Intensity of the light source Shutter speed setting Tripod usage Desired creative affect What are the factors that affect shutter speed choice? ISO sensitivity setting Aperture setting Intensity of the light source Speed of the subject movement Distance from camera to subject Camera movement Tripod usage Desired creative affect On following pages are the full, half and third stops settings for shutter speed, aperture and ISO along with usage comments and suggestions. 3

4 Selecting a faster shutter speed will freeze the motion of moving subjects. Freezing low flying airplanes or race cars that are close to the camera Birds in flight, moving vehicles in bright lighting situation Mountain biking, runners and fast moving athletes Kids playing, dogs running Portraits, flash photography, stationary subjects Limit for hand-holding the camera Panning fast moving subjects at distance Blurring people walking Blurring fastflowing water Shutter speeds in this range will freeze motion on subjects that are moving extremely fast. Shutter speeds in this range will freeze motion on slower moving subjects. Shutter speeds in this range will blur motion on moving subjects. Shutter speeds in this range are good for low light levels or panned action. Shutter Speed Settings Full stop Half stop Third stop 1/8000 1/6400 1/6000 1/5000 1/4000 1/3200 1/3000 1/2500 1/2000 1/1600 1/1500 1/1250 1/1000 1/800 1/750 1/640 1/500 1/400 1/350 1/320 1/250 1/200 1/180 1/160 1/125 1/100 1/90 1/80 1/60 1/50 1/45 1/40 1/30 1/25 1/20 1/20 1/15 1/13 1/10 1/10 1/8 4

5 Blurring slow moving water Selecting a slower shutter speed will blur the motion of moving subjects. Selecting a stopped down aperture will create extended depth of field for grand theme type subjects. Subjects at a wide range of distances will all appear to be in focus at the same time Grand theme type compositions with near and far objects. Everything will appear to be in focus Photographing documents or subjects that require greater depth of field and sharpness. Indoor flash photography or portrait photography Portraits, still life or subjects that do not require an extended depth of field Subjects at one distance will be in focus. Near and far objects will be out of focus Creates very shallow depth of field Apertures in this range create images with a possible vignette. Optimal Apertures: Apertures in this range create images with greater contrast and sharpness. Apertures in this range can be used in brighter lighting situations. Apertures at 2.8 and wider are considered to be a fast lens. Aperture settings in this range are good for low light levels. 1/6 1/6 1/5 1/4 The slowest timed shutter speed is 30 (seconds). Aperture f/stop Settings Full Stop Half stop Third stop f/32.0 f/29.0 f/27.0 f/25.0 f/22.0 f/20.0 f/19.0 f/18.0 f/16.0 f/14.0 f/13.0 f/13.0 f/11.0 f/10.0 f/9.5 f/9.0 f/8.0 f/7.1 f/6.7 f/6.3 f/5.6 f/5.0 f/4.8 f/4.5 f/4.0 f/3.5 1/90 f/3.2 f/2.8 f/2.5 f/2.4 f/2.2 f/2.0 f/1.8 f/1.7 f/1.6 f/1.4 f/1/2 f/1.2 5

6 Selecting a wide-open aperture will create very shallow depth of field on single theme subjects. f/1.0 f/1.1 Depth of field at any given f/stop number is dependent upon the focal length of the lens, camera to subject distance and the sensor size used to capture the image. Selecting higher ISO settings increases the visibility of noise and grain and reduces the quality of the image. Higher ISO settings create images that are less coloraccurate, have fast color/tone transitions and are far less aesthetically appealing. Visible noise and grain increases in the shadow or dark tones and in large areas with a solid color. ISO settings in this range allows the photographer to extend daylight or capture images in adverse lighting conditions It s good to keep in mind that when ISO is increased, image quality is impacted in three ways: 1. Color quality is reduced resulting in less than accurate color rendition. 2. When the image is saved as a Jpeg (high levels of compression) or when the image is enlarged and printed, the result is an image that has a murky appearance. 3. Appearance of small- scale detail is decreased. If the ISO setting is doubled from 800 to 1600, the amount of light reaching the image sensor required for a suitable exposure is halved. Indoors flash photography or portrait photography Low ISO settings create images that are color-accurate, have smooth color transitions and are aesthetically appealing. Scenes with a heavy overcast Sunrise or Sunset Scenes with a light overcast Optimal ISO settings for most Nikon cameras Optimal for the D800/800e and D4 ISO Sensitivity Settings Full stop Half stop Third stop 204, ,400 51,200 40,000 36,000 32,000 25,600 20,000 18,000 16,000 12,800 10,

7 Selecting a lower ISO setting results a higher quality image with less visible noise and grain. 100 L1.0 = 50 L0.5 = 75 ISO rating is an algorithmic value that indicates the image sensor s specific sensitivity to light. The size of the camera s digital sensor determines what ISO setting provides the least amount of digital noise. Putting the Variables Together Here s a workflow you can use when getting ready to take a photograph. L0.3 = 80 L0.7 = 64 Let s begin with the exposure trifecta s three variables ISO, Aperture and Shutter Speed. Variable #1 First decision should be what ISO do I want to use for this photo session? Two considerations: 1. What image quality do you want to create? 2. How intense is the light source? Refer to the ISO breakdown to select the appropriate ISO setting. Then enter the ISO value under the S in the equation. Variable #2 Next decision should be do I want to control depth of field or motion? Which is the critical element for this photograph? Depth of field? What aperture setting will create the desired area of focus? Enter the f/stop under the I in the equation. Motion control? What shutter speed do I need to select to either freeze or show the motion? Enter the 1/second value under the T in the equation. Refer to the Aperture or Shutter Speed breakdown to select the appropriate setting. Variable #3 The decision you made for variable #2 also determines which variable you re willing to change to achieve the desired exposure. If depth of field is the critical element then shutter speed is the changeable element. If motion control is the critical element then aperture is the changeable element. ISO Aperture Shutter Speed Exposure S + I + T = E Exposure Modes To select the appropriate exposure mode use the following breakdown: Critical Element Exposure Mode(s) Variable(s) that can change Depth of Field Aperture Priority or Manual Shutter Speed Motion Control Shutter Priority or Manual Aperture Doesn t Matter Programmed Auto Shutter Speed or Aperture Remember when you change one of the three variables the other two variables are impacted. Controlling the Exposure (E) If you ve selected Programmed Auto, Aperture Priority or Shutter Priority Auto exposure modes use the cameras Exposure Compensation feature to adjust the brightness of the image. Depress the Exposure Compensation button, rotate the main command dial to select a + (brighter) or (darker) setting. If you ve selected Manual exposure mode the exposure compensation button becomes inactive and cannot be used 7