W2 – Aperture

SHOOTING IN RAW

RAW vs. JPEG

JPEG files are processed within the camera. How exactly they are processed varies from model to model. While colour temperature and exposure are set based on your camera settings when the image is shot, the camera will also process the image to add blacks, contrast, brightness, noise reduction and sharpening and then render the file to a compressed JPEG. These files are finished and can be viewed and printed immediately after shot.

JPEG:

A standard format readable by any image program on the market or available open source
Exactly 8-bits per color (12-bits per location)
– Compressed (by looking for redundancy in the data like a ZIP file or stripping out what human can’t perceive like a MP3)
– Fairly small in file size (an 8 megapixel camera will produce JPEG between 1 and 3 MB’s in size)
– Lower in dynamic range
– Higher in contrast
– Sharper
– Immediately suitable for printing, sharing, or posting on the web
– Not in need of correction most of the time (75% in my experience)
– Able to be manipulated, though not without losing data each time an edit is made – even if it’s just to rotate the image (the opposite of lossless)
– Processed by your camera

RAW:

RAW files are uncompressed and unprocessed snapshots of all of the detail available to the camera sensor. Because RAW files are unprocessed, they come out looking flat and dark. RAW images need to be viewed and processed using your camera’s software or with programs like Adobe Photoshop, Lightroom, Aperture, etc. prior to being ready for display or print.

– Typically a proprietary format (with the exception of Adobe’s DNG format that isn’t widely used yet)
– At least 8 bits per color – red, green, and blue (12-bits per X,Y location), though most DSLRs record 12-bit color (36-bits per location)
– Uncompressed (an 8 megapixel camera will produce a 8 MB Raw file)
– The complete (lossless) data from the camera’s sensor
– Higher in dynamic range (ability to display highlights and shadows)
– Lower in contrast (flatter, washed out looking)
– Not as sharp
– Not suitable for printing directly from the camera or without post processing
Read only (all changes are saved in an XMP “sidecar” file or to a JPEG or other image format)
– Waiting to be processed by your computer

APERTURE

The exposure triangle.
A photograph’s exposure, as captured by your camera, determines how light or dark an image will appear. The three fundamental elements of exposure are aperture, shutter speed and ISO, which together make up what we call the exposure triangle.

These three elements form the foundation of successful photography and we will be looking at each, one by one, over the next three weeks.

Let’s start with aperture.

What is aperture?
The aperture is a hole or diaphragm within the lens, a small set of blades that controls how much light will enter the camera. The blades create a octagonal or circular shape that can be widened or narrowed.

If you shoot with the aperture wide open, more light is allowed into the camera. If the aperture is closed down, it only allows a much smaller amount of light to enter the camera.

How is aperture measured?
Aperture is measured in ‘f-stops’.

Moving from one f-stop to the next either doubles or halves the size of the opening in your lens, and the amount of light getting through. These are called ‘stops’, and shutter speeds work in a similar manner.

A high f-stop (e.g f/22) means that the aperture hole is quite small; a low f-stop (e.g f/2.0) means that the aperture is wide open.

What does the aperture do?
The aperture does two things, one technical and the other creative.

First, the aperture changes the amount of light let in to the camera’s sensor, thereby affecting the exposure.

Second, the aperture affects the ‘sharpness’ of the image, which we commonly refer to as depth of field.

What is depth of field?
Depth of field (DOF) is the area of your image that is in focus.

More specifically, it’s the distance between the nearest and the farthest object that are in focus.

A large depth of field means that most of your image will be in focus whether it’s close to your camera or far away (and is measured with a larger number/f-stop).
A small (or shallow) depth of field means that only part of the image will be in focus and the rest will be blurred (and is measured with a smaller number/f-stop).
What is the relationship between aperture and depth of field?
The aperture controls the depth-of-field.

A wide aperture:

Lots of light
Small number (e.g. f/2.0)
Shallow depth of field (not much in focus)
A narrow aperture:

Very little light
Larger number (e.g. f/16)
Large depth of field (a lot in focus)
What other factors affect the depth of field?
In addition to aperture, depth of field is also affected by the focal length of the lens, the size of the camera sensor and distances between you, the subject and the background.

Focal length: The longer the focal length is, the shallower the depth of field will be.
Sensor size: A larger sensor size allows you to achieve a shallower depth-of-field.
Distance between you and your subject: The closer you are to your subject, the shallower your depth of field will be.
Distance between the object and background: The further away the background is from the subject, the more blurred the background is going to be.

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