Casper College, 3/6/19
Instructor: Karel Mathison
- Self Timer
- Playback & Deleting Photos
- Filters (UV, Polarizing, Neutral Density)
- White Balance
- Exposure Compensation
- Exposure Bracketing
- RAW vs. JPG
The timer introduces a delay between press of the shutter release and opening of the shutter curtain. This delay is configurable. My camera supports delays of 2, 5, 10, and 20 seconds.
There are two situations where a delay may be useful. If the photographer wants to take a picture that includes themselves, time will be needed to move into position and pose. A family portrait isn’t quite the same without all members of the family in it.
The second situation is when the camera is mounted on a tripod and the photographer wants to minimize camera shake. Pressing the shutter release introduces a small amount of vibration. Setting the timer to introduce a delay allows that vibration to stabilize prior to exposing the photo sensor.
Playback & Deleting Photos
Reviewing photos that have been taken affords the opportunity to make camera adjustments while the subject is still around for another photo. When reviewing an image, it’s important to zoom in to inspect different parts. Specific things to look for include:
- Are the eyes in focus?
- Is the shutter speed fast enough to avoid blur or slow enough to get the desired blur?
- Is the aperture size producing the desired bokeh?
- Is the image over or under exposed?
- Is the composition desirable?
Deleting photos is pretty simple. Using the camera for deletion requires a burdensome bunch of button presses. It’s faster an easier to insert the SD card in a computer and delete the files from it. This, of course, limits space on the SD card when taking pictures. SD cards are cheap. If storage space is a concern, you’ll be better off investing in a second card.
Filters screw onto the front of the camera lens and alter the incoming light prior to exposing the photo sensor.
UV filters eliminate the ultraviolet light. In most cases they have little to no effect on an image. However, they will sometimes eliminate artificially introduced haze in the sky.
Karel indicated that there are two schools of thought: always use UV filters and never use UV filters. The argument for always using them is that they protect the camera lens from dirt and grit damage. It’s much cheaper to replace a filter than a camera lens.
The argument for never using them is that they place an additional layer between the subject and the image. This layer can introduce image aberations if polluted with finger prints or specks of dirt.
These are also known as circular polarizing filters. These filters contain two pieces of glass. The outer one can be rotated to change the plane of polarization. Just like polarized sunglasses, these filters eliminate glare from images. This glare is common when photographing things like water, snow, or vegetation.
Polarizing filters are most effective when the subject is lit from the side. They are far less effective with subjects that are lit from directly in front or behind.
Karel intends to talk about these filters more next week. We couldn’t do it this week because we needed sunlight. Hence, it’s been delayed until after the beginning of daylight savings time.
Neutral Density Filters
Neutral density filters change the quantity of light entering the camera. In bright light settings the photographer loses control of the camera. If a large aperture is desired to limit the depth of field, the photosensor can be flooded with light creating an over exposure. Similarly, if motion blur is desired, setting a slow shutter speed can also over expose the image. To work around these challenges a neutral density filter can be attached. The reduction in light changes the tradeoff between shutter speed and aperture size restoring the photographers creative control.
Neutral density filters are also available as split filters. This means one half of the filter is neutral density while the other have is completely transparent. These filters can help with landscape images that include a bright sky. Aligning so that the neutral density portion is over the sky allows good contrast for clouds and mountains while the transparent half of the filter retains the contrast of the darker foreground.
There are a variety of light sources each of which affects the image in different ways. White balance selections make images under different sources look more natural. My camera is equipped with eight
- Auto – Allows the camera to decide on the most appropriate setting.
- Incandescent – Adjust for incandescent lights that have a tungsten filament.
- Florescent – To be used with florescent lights.
- Direct sunlight – For sunny days outdoors.
- Flash – This adjusts for the camera’s built in flash and likely works well when a flash unit is mounted.
- Cloudy – For cloudy days outdoors.
- Shade – This adjusts for photos taken outside on cloudy days.
- Preset Manual – This allows the camera to set the white balance to a predetermined value. There are two ways to get the predetermined value. Option 1. The camera can record it by holding a white or gray object in front of the camera under the desired lighting conditions. Option 2. The camera can determine the WB setting from a photo stored on the SD Card.
Image preview can be configured to show a histogram of pixel brightness like the one below. The horizontal axis is the pixel brightness. The vertical axis is the number of pixels having that brightness. Examination of the histogram, therefore, reveals whether the image is over or under exposed. Armed with this information, the photographer can adjust the aperture size, shutter speed, ISO setting or exposure compensation and retake the picture with better results.
An under exposed image will have a large number of pixels near the left edge of the histogram and likely will appear to be clipped on the left. When this happens, detail will not be distinguishable in the dark areas of the photograph. Before retaking the picture, make adjustments to let more light reach the photosensor.
Conversely, and over exposed image will have a large cluster of images on the far right and will likely appear clipped along that edge. You will need to restrict the light entering the camera prior to retaking the picture.
You have several options to addressing under/over exposure:
- Aperture size: Opening the aperture will let more light in, but will also narrow the depth of field.
- Shutter speed: Slowing the shutter speed will allow more light in, but may result in blurred motion.
- ISO Setting: Increasing the ISO setting will make the photo sensor more sensitive to the light that enters the camera, but increase the noise in the image.
- Exposure Compensation: Depending on what mode the camera is in, exposure compensation will make fine adjustments to any of the above.
Exposure compensation alters the amount of light entering the camera in increments of 0.3 F-stops within the range -5.0 to 5.0 on my camera. Rarely will the photographer want to adjust it by more than a full F-stop. If an adjustment larger than that is needed, it is generally best to make manual adjustments of the camera before tweaking it with exposure compensation.
Exposure compensation actually works differently depending on the camera’s mode setting.
- Aperture Priority Mode: EC adjusts the shutter speed and ISO setting.
- Shutter Priority Mode: EC adjust the aperture size and ISO setting.
- Program Mode: EC adjusts the aperture size, shutter speed, and ISO setting within the limitations defined by Program Mode.
Exposure bracketing is a feature not supported by my camera. When exposure bracketing is enabled, a burst of three images with different exposures are taken. One will be at the ideal exposure settings according to the camera’s mode setting. The other two will be 0.3 F-stops above and below the ideal exposure setting. This allows the photographer to decide when they are reviewing the images which is the best.
Some cameras also have a feature that allows the three images to be automatically combined into a single image by taking the best parts of each image. It’s often the case that you don’t want to do this. For example, if the subject contains motion, parts of the image will appear out of focus because those parts are in a slightly different position in each of the three photos.
RAW vs. JPG
DSLR cameras allow the image to be stored in either a RAW or JPG format. Most allow the image to be stored in both formats. The RAW images contains everything about the photograph. The JPG is a more condensed and compressed version of the image.
|Image Size||Large (~20 MB), varies w/ resolution||Medium (~5 MB), varies w/ resolution & compression|
|SD Card Write Time||Long||Medium|
|File Contents||Contains absolutely everything about the image including multiple copies at different white balances.||Contains only one image at the camera settings and a limited amount of metadata.|
Karel’s recommendation is to set the camera to store both file formats unless storage is too limited or the write time is a problem. The write time might be a problem if the photographer desires a rapid burst images. Each of these images has to be written to the SD card before the next image will be taken. As a result, long write times limit the speed of the burst.