Pixels make pictures

Many of the basics of photography; good composition correct exposure and understanding light, are the same whether you’re using a digital camera or if your images are recorded onto film. For all the many advantages that digital offers, the process throws up a few complications that confuse and frustrate the uninitiated.

Because images are recorded onto an electronic sensor and each image is made up of millions of pixels, the importance of understanding what’s meant by resolution starts to take on a new level of importance if you plan to use the image in any business or professional context.

Manufacturers will market their cameras with headline grabbing claims of the number of pixels their latest model boasts.  Not many years ago, an 8 mega pixel camera was the preserve of the professional, now some mobile phones come fitted with an 8mg camera. Top end professional cameras feature 20Mg sensors (or more), that’s 20 million pixels, in an area the size of an old style 35mm transparency.  The level of detail these cameras can capture is astonishing and coupled with the best lenses on the market they can produce images of incredible technical quality.  However, the quality of the finished photograph still requires the person with their finger on the shutter release to know what they’re doing.

However; taking the picture is just the beginning, the difficult bit comes when you decide what you’re going to do with it.  The question of image resolution rears its head when considering the use of the picture.  Resolution isn’t simply how sharp an image is, or how bright the colours are.  In digital terms, the resolution of an image determines what it can and can’t be used for.

High res image

Low res image
Image B
Image A

Take these two pictures as an example, they may look identical and in many ways they are.  They both measure 12 in x 8 in and have been produced from the same initial digital image.  The one on the left can be described as high-resolution and the one on the right as low-resolution.  The difference is seen when you enlarge the pictures.

Detail A
Detail A

The high resolution picture is reproduced at 300 dpi (dots per inch) meaning that a single one inch square is made up of 90,000 (300 x 300) dots (or pixels).  Each pixel is a single colour and when seen alongside its’ neighbouring pixels creates subtle changes of shade and smoothes lines into gradual curves.  With so much detail in the image, it’s possible to enlarge the image to poster size or bigger without compromising on quality.  It’s also possible to enlarge a small section of the picture and produce an acceptable image. The downside to this quality is that the digital file is very large – 8.64 million pixels – too large to send as an email attachment or include in a webpage without slowing download speed to a snail’s pace.

Detail B
Detail B

The low resolution picture is reproduced at 72 dpi, thus considerably reducing the overall file size, 5,184 pixels per square inch, or less than 500,000 pixels in total, making it much more suitable for online use. When reproduced at 100% of its size i.e. 12” x 8”, it remains a high quality image.  The downside comes when that image is required as the backdrop to an exhibition stand or is wanted to illustrate a magazine article.  As can be seen from the same detail shot as above, the quality of the image falls apart and the image ‘pixelates’ with jagged lines and the individual pixels becoming clearly apparent.

The print industry, especially glossy magazines, demand high resolution files, a minimum of 300 dpi and sometimes even higher depending on the type of publication the image is being used in. There is an added complication when producing images for print; as the printing industry work with a four colour (CMYK) ink process and  images on the computer are produced using three colour (RGB) light projection, but that’s the subject of another post.

The way a digital image is captured in the first place determines what can be done with it and what resolution it is saved as.  While it is possible to reduce a high resolution image to low resolution, the operation cannot be done in reverse.  If images are only required to illustrate a website or send as an email attachment, then the pictures taken by a compact camera or even a decent mobile phone will be suitable.  Provided there are no plans to reproduce the images any bigger than postcard size, the resolution will not be a problem.

To produce high resolution images whose intended use is in a business or professional context then they need to be captured by a camera capable of shooting RAW files.  Depending on the manufacturer, the designation of the files may vary but the principal remains the same. The digital file uses the full power of the sensor and no compression takes place to reduce the file size to save storage space. RAW files are sometimes referred to as digital negatives.

Any camera capable of shooting RAW files will usually be supplied with the manufacturers own software application to process and convert them into a more common format (such as jpeg) to enable them to be viewed by the different media viewing software packages supplied with almost every computer sold.

The beauty of RAW files is that they give the photographer huge scope for adjustment and manipulation and they can be saved at whatever resolution is required for the finished picture.