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Blog: Compression

29/11/16 – Compression

When producing and exporting videos, one of the main features for consideration is the video format and the file format. These two terms are often mistakenly used interchangeably, however there is a distinct difference.

The file format is the extension to the end of the filename. Common examples in everyday life include .docx, .pptx, .pdf and .exe. Those more related to video and film include .mov, .flv, .exr, .tiff and .avi. The file format will decide what type of application can open, read and handle the file. For example, VLC media player can accept most of the common file types. Apple iPhones and iPads however cannot read or open flash files.

vm_videocodecs_00

The video format, sometimes called the codec, determines how compression is added to the data itself. Common examples include Animation, Apple ProRes, H.264, REDCODE and XDCAM. The video format largely determines the quality of the file once it has been opened in an appropriate piece of software.

Some video formats are described as ‘lossy’, and others as ‘lossless’. This is because of the differing ways in which video codecs compress the files. A .raw image file is lossless, because the camera records all of the light information that the sensor records – this can result in very large file sizes. However, a .jpeg, for example, is a lossy format. As the file is compressed, some of the sensor data is thrown away. Under normalcircumstances, the effect is not noticed, and file sizes are greatly reduced. If the compressed images are enlarged too much, however, the result of the compression can be seen as the image would not be clear.

Another way to describe the quality of audio or video files is bitrate. This is a measure of the amount of data transmitted in a given amount of time, usually a second – either Kbps (Kilobits per second), Mbps (Megabits per second) or less commonly Gbps (Gigabits per second).

Below are four videos. They all have exactly the same content, but each is encoded with different settings. The first one is a lossless compression with a 10/10 quality. The next is a lossy compression with a 8/10 quality, and the remainder are lossy with 5/10 and 3/10 quality respectively. The difference that the compression makes should be clear from the buffering time when comparing each video, as well as the resolution of the video – especially when in full-screen mode.

Video 1: H.264 – Maximum Render Quality – 1920 x 1080

https://youtu.be/j1vU5U3V8bI

Video 2: MPEG-2 – HD1080p – 1920 x 1080

https://youtu.be/MYOOqSxa1tk

Video 3: Quicktime – NTSC DV Widescreen 24p

https://youtu.be/1vfva01XuOk

Video 4: MPEG-4 – 3GPP – 352 x 288

https://youtu.be/07foheOaCv4

References and Further Reading:

Categories
Blog

Blog: Composition

11/10/16 – Composition

In today’s lab, we went over the basics of composition for photography, including techniques such as the rule of thirds, frames within a frame, the Fibonacci spiral, and more. The main task was to go out from Tower C and take a series of photographs on our mobile phones. Each of these had to be around a certain theme: Line, Space, Time, Motion, Volume or Mass, Value, Texture, Colour, Shape.

Below are my submissions for photos in each of the nine categories along with a few notes on why they were taken and how they were edited. They were all taken on my iPhone, and are all square. This fits in with the rest of my photography work from the last academic year, and also with the regular and geometric design of my website. I prefer regular shapes that can be tessellated and arranged in a grid. I briefly edited each one using Adobe Photoshop before uploading them.

Value: This image is edited simply by increasing the contrast levels and decreasing the saturation, to make the numbers on the lock really stand out from the rest of the metal.

Line: For this image, I liked the way the crack drew the viewer’s eye across the entire width. It is a type of line, however it is not uniform and therefore interesting to look at.

Time: For this category, I tried to think outside the box a little. If I stood in the same place, my own shadow on the floor would grow, shrink and rotate over time, in a similar way to the shadow on a sundial moves.

Texture: This image was fairly boring in my opinion, even after increasing the saturation and variance in Photoshop. In order to make it more interesting and visually appealing, I rotated the image round 180 degrees. However, this made the composition not look right, so I then flipped the image about a vertical axis.

Space: The majority of this image is just empty sky. The tall chimney, at an angle, occupies only a small space. I edited the saturation slightly to make the blue more intense- thus giving the impression of nothingness.

Shape: Choosing an image to represent this category was fairly tricky. In the end I settled on this one as there are multiple simple, geometric shapes present. The corner where the wall and floor lines intersect creates interesting angles, as well as the circular ceiling light and cuboidal emergency light on the wall.

Motion: I found this category the most challenging of the whole task. Finding something to represent motion while still being a photograph with a well thought-out composition was difficult, so instead I used an object that most people would be able to readily associate with motion instead. Upon seeing the image, the motion of an opening door springs easily to the mind.

Mass/Volume: I chose this photo for the Mass/Volume category rather than the Colour category because I liked the effect it created, where you can’t tell whether the shape is going inwards or outwards – it is a 3D image without the viewer being entirely sure what they are looking at.

Colour: For this image I created a mask in Photoshop and desaturated the building to a point where it is pretty much a greyscale image. This leaves the plain, unedited blue of the sky as the main feature of the photo. I liked the way there is a very subtle change in the shade of blue from top to bottom.

References and Further Reading:

 

Categories
Photography

Kira

kira

For the Studio Portraits section of the Photography module. This photo features Kira facing away from a single softbox light, in front of an illuminated white background. The photo was slightly over-exposed so this was corrected in Photoshop.

Categories
Photography

Seb

Seb

For the Digital Portfolio, one of the photography themes that I have picked was studio portraits. This photo shows Sebastien posing in the studio. Using a single light and a low camera angle, it gives the impression of scale and intimidation. I removed the background lights and ceiling using Adobe Photoshop.