workshop session 2 – framework
The second session of the Introduction to Digital Photography workshop met January 27.
As we reviewed Assignment one, it became clear that the image quality and image size wasn't always obvious on the surface. Only after zooming deeply into an image could we begin to see the image degradation and artifacts symptomatic of lower-quality JPEG compression.
If you are only going to use your photos for email, on your own computer (like a screen saver for example), or post them on the web (i.e. flickr or Picasa), JPEG worked very well.
If our photos are going to be printed in larger formats (8×10 or larger) or published by online services or print bureaus that require high-resolution images then camera RAW is the better choice - if available.
I also believe that if you intend on pursuing creative digital developing, the deeper quality of the camera RAW image will offer significantly more luxury of expression. That said, here's a suggested guideline:
- If your camera can only shoot JPEG, use the highest quality available and largest image size available. This will give you the most headroom in post-processing. Changes needed for emailing or publishing on a website can be done later, but image data lost when the shutter is pressed can never be regained later on. It is gone forever.
- If your camera can shoot any of the camera RAW formats, use that. If DNG is available, use that. this is the best solution.
The only caveat might be that if you're traveling abroad without access to the internet or some other way of offloading your memory cards, you may want to take into consideration how many images your memory card(s) can store at the various size/quality combinations. The higher the size and quality, the fewer images a memory card can hold. Most cameras display the number of images remaining on the memory card. Purchasing additional cards is a good option and will give you more capacity.
The new topics for this session are camera operation, including
- shooting modes,
- the shutter button,
- digital versus optical zooming,
- using shake reduction,
- ISO settings, and
- white balance
There are several "one-off" basic camera operation functions that don't warrant a session alone, so we dealt with them here.
The one goal of almost everyone in the workshop is to "get off automatic mode." To do that we need to quickly explore a simplified model for "exposure", a function of shutter speed and aperture ƒ-stop.
All cameras, digital or otherwise, operate on these same variables.
Digital SLRs allow more control over these variables while a digital point-and-shoot takes control over these variables (as well as flash and focal length). How the camera manipulates these variables depends on it's "shooting mode".
- most digital SLR cameras have a mode dial
- point-and-shoot cameras will have symbols like those shown here in green. they are usually found under your MENU or FUNCTION (Fn) button.
For digital SLRs these are the manual, programmed and priority modes commonly found in white:
- M – manual mode
Lets you capture a picture with full creative control; you set exposure time (also called shutter speed, i.e. 1/60th of a second) and aperture ƒ-stop (i.e. ƒ/4.0) .
- P – program mode
Sometimes called PRO mode or Hyper-program mode. This will vary by camera; digital SLRs offer a greater degree of control, point-and-shoot cameras don’t.
For example, P mode on my Pentax K20D gives me maximum flexibility and control while the camera ensures a good exposure. If I set the aperture ƒ-stop, the camera figures out the needed exposure time. If I set the exposure time, the camera selects an appropriate ƒ-stop.
- Tv stands for exposure Time priority mode. In this mode only the exposure time or shutter speed can be adjusted, the camera picks the aperture ƒ-stop.
- Av stands for Aperture priority mode. Here only the ƒ-stop setting can be adjusted, the camera selects the shutter speed.
- B or Bulb mode (not on all cameras). The shutter operates for as long as the shutter release is held down. Useful for the very long exposures (typically more than two seconds) required for night scenes, fireworks, etc.
The green or automatic, pre-programmed modes are also sometimes called scene modes. Automatic mode may be a green square, the words AUTO in green, or, confusingly, P mode. On a point-and-shoot cameras, P will usually stand for automatic pre-programmed mode; on a digital SLR cameras, P mode usually refers to program, PRO or Hyper-program mode.
|Sports or Action. The camera will use the fastest shutter speed to freeze motion.|
|Portrait. The camera will use larger aperture values resulting in a shallower depth of field. This keeps the subject in focus while allowing the background to blur.|
|Landscape. The "opposite" of portrait; uses a smaller aperture to get a deeper depth of field, ensuring both foreground and background are in focus.|
|Night Portrait. Usually uses the flash in red-eye reduction mode.|
|Macro Mode. Here the camera uses a shorter focal length allowing you to get within inches of your subject.|
You may also find other green modes, sometimes called scene modes
|Night Scene||Surf and Snow||Text||Sunset|
In these modes, all the cameras settings, including flash and focal length, are pre-programmed to help you get the best picture under each of these conditions. Your manual should help you understand how these different scene modes set your cameras shutter speed, aperture ƒ-stop, flash and focal length settings.
When I asked how many in the workshop had noticed that the shutter button has three positions or stops, most had noticed but many weren't sure what they meant.
- When the shutter button is fully released (i.e. not pressed), the camera starts the automatic turn-off timer. All automatic functions on the camera are turned off (typically auto-exposure and auto-focus controls).
- When the shutter button is pressed halfway, the cameras automatic functions are activated. The camera sets the exposure and after focusing on the subject, locks that focus point. If you turn the camera slightly left or right, moving the subject to the edge of the frame, the subject will remain in focus as long as the shutter button is kept pressed halfway.
- And lastly, when the shutter button is completely pressed, magic happens and viola - one image is captured.
Digital vs Optical Zoom
Digital zoom is one of my favorite bones of contention with camera salesman and misleading marketing hype.
- Optical zoom changes the field of view by changing the focal length of the lens in your camera. There is no loss in image quality.
- Digital zoom crops an image down to a smaller size and then interpolates the result back up to the pixel dimensions of the original. This is accomplished electronically, without any adjustment of the camera's optics. No optical resolution is gained in the process and the higher the level of digital zoom the more image quality will suffer.
The centre image is our original photo; the focal length is 50mm. The left image is "zoomed" in optically to 200mm (4 times); we retain all the detail in the scene. The right image is also "zoomed" in 4 times, but a significant amount of detail has been lost.
The warning here is to avoid increasing the zoom range beyond the optical range into the digital area. It's not too pretty.
Most digital cameras offer shake reduction, also known as image stabilisation. Image stabilization allows the use of shutter speeds 2–4 stops slower (exposures 4–16 times longer) or aperture settings 2–4 stops smaller (4–16 times more light as well as a deeper depth of field)
The warning here? If you are using a tripod, turn this off – the cameras mechanisms will fight with the tripod and may result in an out of focus or blurred image!
To a greater or lesser degree, all digital SLRs and most point-and-shoot cameras allow control over the ISO (International Standards Organisation) value. This number represents how much amplification is applied to the electrical signal being read from the image sensor.
Image sensors generate an electrical signal when light strikes it. They also generate sporadic or random "noise". At lower ISO levels (200 or lower) this noise doesn't become apparent in the image data. At higher amplification or ISO levels the entire sensor signal is amplified, noise and all.
Think of the older home music systems. At low volumes the hiss and hum wasn't too perceptible. But if we turn the volume up, the noise becomes more and more obvious. The same thing is happening in our cameras.
Low ISO levels are usually fine for well lit situations; keep your ISO levels at 200 or below. This will ensure sharper, clearer images. In less well lit situations you may have to "turn up the volume" to get a good exposure by turning the ISO to a higher number.
But be careful. The higher the ISO the more noise will be evident. While most prosumer digital SLRs offer ISO values over 800, sometime up to 12,800), I don't recommend going any higher than 800. My personal experience has shown that the noise levels are not acceptable above 800.
That wraps up the one-off camera operation part of this workshop session.
This sessions assignment delves into the man – machine conundrum one step further … white balance. Onward to ... assignment 2.