Pixels!

 Recently I saw a copy of a magazine that should have been classy. Corporate, for a big company. But even the front page is distorted with pixelation: the photo does not look smooth, but the image consists of little squares. This is not supposed to happen: if a photojournalism student at the Polytechnic submits pixelated work, he/she fails the assignment. This is a very basic concept in digital photography.

Let me explain:

A digital photo is made up of little squares called pixels.

photo 1

Photo 1 looks fine, but if you look at the enlarged section in the blue frame, you can see that the image is built up of squares. Each of these squares gets a colour, and together they build up the image. These squares are called pixels, short for picture-elements. The trick is that the pixels need to be so small that our eyes cannot discern the individual pixels. Then the image looks smooth, and that is what we are looking for. In the printing process the pixels are translated into dots, pixels are square, dots are round. But one pixel translates into one dot. High quality printing on high quality paper uses very small dots, so we see a very smooth image. That means we need many dots to cover a certain area. On cheaper paper, like newsprint small dots would get smudgy, the paper would soak up too much ink and the image does not look good. So on low quality paper bigger dots are used. In a newspaper you can easily see the individual dots, while with high quality printing like the Elle or National Geographic magazines the dots are so small that for my eyes (I am older these days and my eyes are not as good as they used to be!) it is impossible to distinguish the dots, and the whole thing looks very good. Smaller dots means you need more dots for a certain size photo, and that means you need many pixels.

The number of pixels is called resolution. In short: the higher the resolution, the higher the image quality, but also the bigger the file size. The file size is measured in Mb (megabyte), and a hi-res file can easily be more than 30 Mb. Fortunately computer storage space is cheap, with external hard drives of 2 Tb (terra byte) and more, and memory cards of 16 or even 32 Gb (giga byte). So we should not worry about file size too much, unless we need to send an image over the internet. 

Mount Mulanje, high resolution

Mount Mulanje, low resolution.

The panorama photo of Mount Mulanje shows the effect of low-res: the hi-res version is sharp. While the low res version was made the same size, it shows a lack of information by being un-sharp. Now this is internet, where images are always rather low quality, due to the low resolution of a computer screen, and to the need to load pages quickly over the web. A hi-quality file is bigger, so it takes more time to load, which slows down the user experience. With print you don’t have this, and there images on high quality paper can be much, much better quality. So there the difference is even bigger.

If you need a quality image, so for every professional application, you want to use the maximum resolution your camera is capable of. Strangely, some manufacturers do not set the highest resolution as factory settings. So if you want good images, go to the shooting menu of your camera and set the resolution for the highest the camera has, and set the image quality for jpg high, sometimes called jpg fine. Even better is raw, professionals habitually use raw files, which store all the information available, which means the highest image quality. Raw files are bigger than jpgs, the extra file size stores extra image quality. The drawback of raw is that photoshop and other applications cannot work with raw files directly, you need to convert them with (again) photoshop or a raw file converter (to tiff for the best quality, or jpg for smaller files. When you buy a camera, it comes with a disc with software, the raw file converter for your camera is on the disc). This makes your workflow slightly longer but the better image quality is worth it in most cases. I rarely use another file format in my camera. Some cheaper model cameras are slow storing the bigger raw files, so if you are doing action photography, this may be a factor in your decision to use raw or jpg.

It is perfectly possible to make image files small, which is convenient. But the only way to do this is: throwing information away. And once the information is gone, it is not possible to retrieve it. When you save an image in jpg, photoshop gives you a dialogue box with a slider between ‘small file’ and ‘large file’. Large file gives better image quality, and small file gives a smaller file. For professional application I recommend to not go below setting 9. If you need to transfer your images over the internet, services like we-transfer, dropbox, or bigfile.com make it possible to send large files to anywhere on the planet earth. 

low quality jpg

high quality jpg

In the photos you can see Vivian in low quality (quality setting 1), and in hi quality (quality setting 9). Note that in low quality her skin features are not smooth and the background dark grey is in little squares, instead of smooth gradients. Well-paying clients deserve the best quality, and they will not accept images in low quality. (In my opinion we should all avoid low-paying clients, so that the profession is upgraded and we can all make a good living).

If you need to compress an image for transfer over the web, or internet use, it is recommended you keep the large file, that came straight from the camera, in your archive. You may have another client requesting the image for profi use, maybe even a billboard or large banner, and then they need the best quality file.

I recommend not to use the Microsoft Photo Editor or programs like it for any professional use. It is fine for sharing a low quality photo with friends, but too crude for professional use.