Camera College
What’s the score with raw? Marcus Hawkins explains photo file formats
One of the fundamental decisions you need to make before you adjust the exposure on your camera, focus the lens and take a photo is to select the file type your pictures will be recorded in. Not only does the file type determine the image quality, your choice affects the number of shots you can take and even the speed you can record them at. DSLRs and mirrorless cameras typically offer two different file types: JPEG or raw. JPEG was developed for digital photography, and is now the most common file format for photographs. Not only can JPEGs be shared and viewed easily, they come in small file sizes so you can fit more of them on memory cards and hard drives. To achieve this small size, JPEGs have to be compressed, and some picture information has to be discarded in order for this to happen. The more compressed a file is, the more the image quality deteriorates. Your camera will allow you to choose the level of compression applied, but it’s always best to stick with the highest quality/lowest compression option unless you really need to save some space on a memory card.
As well as being able to set the JPEG image quality, you get a choice of image size – how many pixels you want your image to have. The largest setting uses the full resolution of the image sensor, which means more detail is captured and larger prints can be made. You can also save your images in a number of smaller sizes that have lower pixel counts.
Raw files typically only come in one size: full resolution. But unlike JPEGs, raw files
are uncompressed, and this means they are big files – your memory cards will fill up faster and the photos take longer to process in the camera. That’s one of the reasons that professional action sports photographers tend to stick with JPEGs; the compressed format means that a camera can capture longer sequences of shots before it hits a processing bottleneck and the shooting speed slows down.
A raw file takes the raw data from the camera sensor and stores it in a semiprocessed state (a bit like a digital negative). In order to create an image that you can share or print, such as a JPEG or a TIFF, the raw file needs to be processed. There are a couple of ways that you can do this: either in-camera, with models that offer this facility, or in special raw conversion software. The latter is the better option, as it offers a more powerful and versatile set of controls. Camera manufacturers usually supply raw software with their DSLRs, although third-party software, such as Lightroom, Affinity Photo and Adobe Camera Raw (part of Photoshop and Photoshop Elements) are capable of impressive results. But the
The largest setting uses the full resolution of the image sensor, which means more detail is captured and larger prints can be made
bottom line is that you’re going to end up spending longer in front of a computer.
Regular readers of Digital Camera know that we recommend shooting raw in a wide range of circumstances. The fact that it requires an extra stage of processing is an advantage, as you’re able to carry out alterations to many of the camera’s image settings even after you’ve taken a picture. For instance, you can tweak the exposure, white balance, colours, contrast and sharpening. There are some camera settings that can’t be adjusted later, such as the three elements of exposure – aperture, shutter speed and ISO – which are locked at the time of shooting. Similarly, you can’t change the focus (although there are some exceptions to this rule). Raw offers more creative options, as well as acting as a safety net should you make an error at the time of shooting. Knowing that you can pull some detail back in the highlights if the exposure is slightly off, or warm up or cool down the image with a different white balance setting provides some peace of mind. This is especially true if you’re shooting a once-in-a-lifetime event, such as a wedding.
You can, of course, edit a JPEG image in software, but due to the ‘lossy’ nature of the compression, each time you edit and save a JPEG file there’s a further degradation in quality. There are also some aspects that you can’t change later: shoot a JPEG in black and white, for example, and you won’t be able to recover the colours.
A raw file takes the raw data from the camera sensor and stores it in a semi-processed state (a bit like a digital negative)