Technical Design
Moiré and Aliasing
Moiré is a digital effect that appears when two fine patterns converge to create a third. This often happens with pictures of things like fabrics and architectural parallel lines (things like brickwork).
There are a few different ways of reducing, or altogether eliminating moiré from an image. Some cameras can be fitted with an anti-aliasing filter that can help with moiré problems. However, they can lead to images being a bit softer than may have been intended. Images are generally a little bit sharper without an anti-aliasing filter.
If you don’t have a filter though, moiré can be easily dealt with just by changing the angle, position or focus point of the subject. You must be careful to check your photos when they have been taken so that you can make the appropriate changes.
If you don’t realise moiré on your photos before you get to post-production, then software packages such as Photoshop can help to remove it for you.
Examples of Moiré taken from 'Aliasing' page of Wikipedia.org
(Actual Photo (Left), Moiré effected photo (Right
Aliasing is an unwanted, digital effect that results in picture quality being reduced. It occurs when your cameras processor is not fast enough to pick up a true representation of what it is trying to capture.
Aliasing has a clue to what it does in its name. Since it doesn’t capture true representations of an event, the distorted signal gives you a different image, aka an alias, of the original image.
This following video gives an interesting example of aliasing:
This following video for the Canon 5D Mk2, made by Glenn Przyborski, gives a good visual context and explanation of what Moiré and Aliasing is, as well as having a detailed look at the pro’s and cons of using an anti-aliasing filter.
Video taken from youtube.com
Video taken from youtube.com
RAW & JPEG
RAW is an imaging format that aims to capture the characteristics of a scene, for example the light and colour, and process the picture to the best of the cameras ability. RAW files record all of a pictures metadata, which includes information like the camera used and the camera settings when the picture was taken, such as the ISO, Aperture and the Shutter Speed. As well as this, they also contain copyright and contact information and even keywords to help search the files. Essentially, RAW has a higher image quality than other formats and can be controlled a lot better in post-production. However, this does come at a sizeable cost, as RAW photos are typically 5/6 times larger than JPEG file sizes.
JPEG is a format that uses lossy compression on digital photos that make them easier to both send, and store on the Internet. The ratio of compression can be adjusted, allowing for compromises between the size of the file, and the quality of the image.
‘The Exposure Triangle’
ISO – The ISO in Digital Photography is what measures the sensitivity of the image sensor. The standard settings of sensitivity double as they go up. 100, 200, 400, 800, 1600 and so on. The general rule of the ISO measurement is that the lower the setting, the less sensitive to light the camera is, and the finer the grain.
Aperture – Aperture is simply ‘the size of the opening in a lens when a picture is taken’. This controls the Depth of Field that the picture has when you are aiming to focus your picture. Aperture is measured in f-numbers, for example f/2.8, f/4, f/5.8 etc. Moving from one number to the next will either halve, or double the size of the opening in the lens, and would therefore halve or double the amount of light that the sensor can pick up.
Shutter Speed – Shutter Speed is the amount of time that the shutter in a camera is open and can let light through to the sensor. The shutter speed will determine how much movement you can get in your photo. The speed can be measured in fractions of seconds and whole seconds and the faster your shutter speed is, then the less movement you will capture, and vice versa.
Canon 650-D & Rode Mic
For filming our documentary, and photographing our various projects, we have used using a Canon 650-D. The reason behind this was simple. They produce exceptionally high quality photos and video, and they are also well designed to be easy to use. Its multi-angle screen makes difficult positions much easier to achieve.
The camera also has the ability to record sound with its built in microphone, which isn’t the most desirable choice of recording, but you can use external mics that can plug into the camera like a Rode VideoMic Pro. This microphone is meant for recordable equipment like DSLRs. It’s a condenser mic that gives broadcast quality sound to the product. It has a super cardioid polar pattern that ensures that the only focused sound is coming from what the camera is directed towards as it minimalizes the amount of sound coming from around it. With these two bits of kit, you have a half decent, albeit very basic, setup to start recording with.
Rode VideoMic Pro
White Balance & Colour Temperature
With digital cameras, it is important to always set a white balance. Different lights give off different colour tints and the human brain is able to cope with balancing these colour changes, but the camera is not able to do the same. Doing a white balance will compensate for the lighting of the chosen shooting location, and match all whites in the camera, to all the whites that would be seen when through the real life.
The colour of the tints is dependent on the source of light. All light sources have a colour temperature and are measured in ‘Kelvins’. The spectrum of colour goes from a ‘warm’ red, to a ‘cold’ blue. Colour temperature follows the rule that ‘the lower the Kelvin Temperature, the warmer the light is’.
Gamut
When using digital technology in order to reproduce an image, there is a certain set of colours that the devices can use in order to recreate it. Different devices have a different set of colours available to them. These ranges of colours are known as Gamut, and the different devices, such as scanners, monitors and printers all interpret colours differently. Software such as Photoshop measures the colour value mathematically and it gives you a Gamut warning if there are colours used that would be out of the gamut spectrum for certain devices.
Image Sharpening
When an image appears blurry, it is because the edges of the subject are not clearly defined. Image Sharpening filters aim to make edges look thinner with more definition. Sharpening filters essentially just increase the contrast between the lines that make up the edges, and the surrounding colours. They make the dark pixels darker, and the bright pixels brighter. These filters are necessary because all digital cameras sensors and lenses will blur an image to some degree.
Before (Left) and after (right) of image sharpening
http://www.digital-photo-secrets.com/tip/1485/why-does-sharpening-help-what-does-it-do/