File format choices
What are the best file types for shooting and archiving?
There is a potentially bewildering amount of technical considerations surrounding output and archiving of digital images. From print resolution (think ppi vs. dpi) to colour spaces and paper profiles, a lot of thought must be invested in future-proofing your digital files and making them as versatile as possible. File format choice is one such consideration and with several types in common use, it can be difficult to be sure which is the best fit for your storage purposes. This is made worse by the fact that the common types are often (inaccurately) looked on as interchangeable, with every photographer seeming to favour one type or other for their images. Each format has its own set of advantages and disadvantages, at both the shooting and archiving stages. In this article we examine the best and worst qualities of each type and explain when and when not to use them.
The jpeg (Joint Photographic Expert Group) format is the most universal and user-friendly format. The native format produced by the majority of digital cameras, jpegs can be used almost anywhere, both off and online, with the minimum amount of fuss. As a compressed format, files sizes are relatively small, making saving large numbers of files possible, without taking up large amounts of hard drive space. This also applies to shooting of images – many event and sports photographers choose to shoot jpeg to maximise memory card usage and camera buffer capacity, the format allowing them to fire often unlimited numbers of images at high frame rates. Unfortunately the process of compression requires the removal of some image data, to reduce file size. This has the potential to introduce compression artefacts – noticeable pixelation or colour banding, which can limit the maximum print size of your images. These artefacts are exaggerated by image processing, so the degree to which you can apply edits in software like Photoshop is also capped. The key point of a jpeg file is that it is print-ready straight out-of-camera; you should always aim to get exposure and colour correct at the shooting stage, so that no processing is necessary ofter the fact.
What’s good:- Small file size, maximum compatibility, rapid file handling for quick workflow
What’s bad:- Compressed files, so rapidly degrade if post-processed, Exposure and White Balance are ‘locked’ in.
A format that should be familiar to experienced photographers, RAW files are uncompressed and contain all of the image data output by a camera’s sensor. This provides great flexibility for image editing, allowing photographers to make sizeable changes to exposure, colour and tone, without any noticeable loss of quality. For serious photographic work, it is safer to shoot RAW to enable multiple re-edits and variations to be created in future. While RAW images are significantly larger than jpegs, the biggest disadvantages are in the camera-specific nature of the format. Each manufacturer has its own proprietary RAW image format (Canon CR2, Nikon NEF etc.) and each camera produces it’s own unique data, that is not immediately compatible with every software suite. Every time a new camera is released, applications like Camera Raw and Lightroom must receive updates to enable them to read the new RAW files. Furthermore, as cameras age their files may no longer be supported in new software, potentially limiting the longevity of a photographer’s images.
What’s good: Provides full editing control over every parameter, quality is preserved, versatile.
What’s bad: Larger file size, inconvenience of software compatibility
DNG (Digital Negative)
Adobe’s Digital Negative format is an attractive option for archiving purposes. Sharing the majority of properties with RAW files, namely the quality-preserving aspects while editing, DNG files also have a generic, universal extension which is cross compatible and which has a greater ‘shelf life’. Images can be converted from their native RAW formats to DNG in programs like Camera Raw and be archived for use in several years, without the issue of expired support. Some cameras even have an option to shoot in DNG, rather than their own proprietary formats. The main downside is the file size, which is larger than jpeg and sometimes the original RAW, since all of the camera data is retained.
What’s good: Long-term archiving compatibility, full editing flexilbility
What’s bad: File size can introduce storage space challenges (although so do RAWs)
A Photoshop Document (PSD) is Adobe Photoshop’s Proprietary format and is essential for retouchers wishing to save their work, while retaining their document’s layers. When working on an image that requires a great degree of editing, spanning several hours or days, this format is a huge advantage, as one can close a file and then later continue work from the same point after re-opening. The key issue with PSD is the size of the files which, in the case of an image with many layers, such as when producing a composite for example, can grow exponentially. It is not impossible to generate PSD files that extend into several gigabytes, presenting storage and processing challenges.
What’s good: Preserves layers so you can close, re-open and pick up where you left off, compatible with multiple Photoshop versions
What’s bad: File size, can only be easily read using Photoshop
Tiff files (Tagged Image File Format) are an interesting file type, which some photographers swear by, while others largely ignore it. The biggest asset of tiffs is their uncompressed state – no compression is applied by default, which means all image data is retained. Unlike RAW files however, tiffs are very universal, meaning they can be recognised and read by a vast number of image handling applications. This also means they do not ‘age’ like a CR2 or NEF file, with little risk of becoming outdated and unreadable in 10 years time. The format essentially combines the best aspects of RAWs and Jpegs, so are appropriate for a range of uses. Although not commonplace, some cameras actually shooting tiff files, but this has limited appeal, due to the main negative point when considering the type. File sizes are often very large, eating up card and hard drive capacity far more rapidly than with jpegs. In fact, tiffs are often significantly bigger than RAWs, after being processed in external software. Importantly, tiffs do not forgive large changes to exposure and colour as much as a RAW file, nor do they allow limitless changes to white balance and camera presets.
What’s good: Lossless file format, good for repeated processing applications and re-saves. Long-term archiving compatibility.
What’s bad: Very large files, still not as versatile as RAW