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RAW vs JPEG | Understanding The RAW File Format
In the previous lesson we touched on why setting white balance within the Raw file conversion software was the best method. But to some of you this may mean almost nothing. JPEG is the friendly, universal and familiar file format that we all know well. Raw sounds slightly technical and serious, perhaps something that requires more effort. Well, I'm happy to say that, not only is the Raw file format going to help you become a better photographer, it's also beatifully simple. Let's find out more...
Raw vs JPEG: How they measure up
So, let's cut to the chase and see how these 2 different file formats measure up against each other, before checking out some example images and thinking about when to use which. Here are the vital statistics for Raw and JPEG files:
- An uncompressed file; all information is preserved.
- An unprocessed file. No adjustments to sharpness, contrast, vibrance etc. are made by the camera.
- Processing takes place in special conversion software on the computer. There is terrific flexibility with Raw file processing.
- A large file, with greater resolution, which in turn takes longer to save to the memory card and takes up more space.
- The original file is kept and processed versions can be saved to any chosen file type (e.g. TIFF, PDF, JPEG etc).
- Unsuitable for immediate display or printing.
- Greater dynamic range (tonal range from highlights to shadows).
- Greater bit depth (colour depth), typically 12, 14 or 16 bits/channel (I'll explain what this means below).
A unprocessed Raw file
- Compressed file (lossy), with information permanently discarded by the camera (based on what it judges to be 'least necessary').
- A file that is processed within the camera. Adjustments to sharpness, contrast, vibrance etc. are made.
- A small file, with less resolution, which in turn makes it faster to save to the memory card and take up less space.
- Every adjustment in post-production reduces image quality.
- Suitable for immediate display or printing.
- Smaller dynamic range (tonal range from highlights to shadows).
- Smaller bit depth (colour depth). JPEG files have 8 bits/ channel.
A JPEG file:
The importance of bit depth
Included in the above lists was the respective bit depth of a Raw and JPEG file. You might not be familiar with bit depth, but it's one of the most important factors to consider when weighing up the merits of these 2 file types.
Bit depth basically refers to the colour range of a file. A Raw file, which has a very large colour range, does not necessarily display all of the available colours in an image, it just has them at its disposal.
Bit depth is measured in bits/channel and bits/pixel. There are 3 primary colours, or channels, in photography: red, green and blue. The greater the range of reds, greens and blues available with a given file type, the greater the bits/channel.
So, a JPEG is an 8 bit image; it has 8 bits per channel (which translates as 256 different reds, greens and blues). This can also be described as 24 bits/pixel; there are 24 bits (8x3) available within each pixel. The overall result is 16.7 million possible colours to each pixel.
A Raw file typically has 12, 14 or 16 bits per channel. This could also be described as 36, 42 or 48 bits/pixel. A 12 bits/channel Raw file produces 4,096 different versions of red, green and blue. The result of this is a total of 68.7 billion possible colours per pixel.
So, Raw files are capable of displaying far more colours than JPEG files. But, if 16.7 million colours available per pixel sounds plenty, 68.7 billion is bordering on the absurd! Can we really notice the hugely subtle gradations between this many colours?
Well, no. In fact our eyes can only manage to identify about 10 million different colours at the very most. So, isn't the JPEG v Raw bit depth issue all academic then. No - far from it...
The reason is that when it comes to post-processing images, the added bit depth of Raw files serves to enable far more adjustments before image quality becomes degraded. You really don't have to push and pull the colours of a JPEG file that much before things go pear-shaped.
What happens is, with an 8 bit JPEG file, we demand the colours to go so far - by increasing things like contrast or saturation - but there simply aren't the colours available within each pixel to fulfill this demand. It's like trying to spread a tiny amount of butter over a whole piece of toast.
As a result the colour range is stretched out too thinly, and we start to see step-changes in colour (the butter is dotted around rather than evenly spread, if this metaphor has any life left in it!) This is the posterization that we explored in the tutorial on histograms. It looks ugly, and once you've saved a JPEG file with posterization - that's it, you can't get the original back.
An example of posterization in an image:
On the other hand, the 68.7 million colours available for each pixel in a Raw file give us all the scope we need to make some quite substantial post-processing adjustments. What's more, if you don't like the changes you made, the original file always remains and you can simply go back and re-edit it.
To maintain all 12, 14 or 16 bits of colour in your image make sure you save it as a .TIFF, .PDF or .PSD document. JPEG lossy compression can take place both in-camera and when saving images in post-production.
Processing Raw files
The additional bit depth and dynamic range of Raw files not only gives us the freedom to really perfect images in post-processing, it also allows us to recover mistakes more effectively.
An under/overexposed JPEG photo does not contain enough information to bring back much detail in the shadows and highlights before quality really drops. On the other hand, the exposure of a Raw image can be changed by up to 2 full stops in the conversion software, whilst retaining decent quality.
It's not just with exposure that Raw files give us extra flexibility. There are a whole host of areas where processing a Raw file produces better results. It's not surprising that your computer offers more processing power than your camera. Here are some of the key things that we can fine tune with Raw files:
Vibrance: It's possible to specify the level of colour vibrance in-camera, for shooting in JPEG. Every time you take a JPEG image it will be processed with the level of vibrance of you have selected. With Raw, we can carefully choose where to position the vibrance slider, so it looks just right.
Sharpness: JPEG's have a little bit of in-camera sharpening applied to them immediately, which results in a picture you could happily print out straight away for an adequate print. With Raw the ability to sharpen, and select which areas to sharpen, is much more subtle.
Noise: Noise reduction is one of those post-production areas that has been very tricky for a long time. There are some excellent programs that deal exclusively with noise reduction, but Raw conversion software (like Adobe Camera Raw) is able to offer increasingly good noise reduction, that cuts noise without reducing sharpness. Needless to say, in-camera noise reduction lags a long way behind.
Contrast, clarity and blacks: These are all areas that add punch and a sense of depth to images. An unconverted Raw file looks incredibly flat and 2 dimensional. By contrast, a JPEG has had some minor contrast adjustments made to it. But the contrast, clarity and blacks sliders in Raw conversion software combine to bring Raw images to life more effectively.
Unprocessed Raw file:
The image is dull, flatand lifeless.
In-camera processing makes this a perfectly acceptable image.
Processed Raw file:
Here the white balance has been fine-tuned, the exposure improved, the colours deepened, the sharpness applied (only to clear edges), noise reduction applied and contrast increased. Processing this file took about 60 seconds.
The Basic tab in Adobe Camera Raw
Choosing when to shoot Raw or JPEG
So it might seem that, with all these advantages to the Raw file format, there's never any reason to shoot JPEG. Well that would be wrong, because JPEG has 2 key advantages over Raw: it saves time and space.
So most shoots require you to decide which would be best, and then select the file type in the shooting menu of your camera. Plus, if you're an indecisive type, or the situation merits it, you can even shoot Raw + JPEG (which creates an uncompressed, unprocessed Raw file and a compressed, processed JPEG file at the same time).
So, when might it be a good time to shoot in Raw or JPEG?
Raw: Whenever you really want to capture the full range of tones and colours in a scene, and have the ability to adjust them flexibly later. For me, the most common example of this would be landscape photography. Landscape photos are all about detail, depth and tonal range. It's such a shame to discard information by shooting in JPEG.
Another good reason to shoot in Raw is when the lighting conditions are very challenging, meaning there's a good chance you'll have to make corrections to some images. Equally, when you're under time-pressure, like shooting the 'big moment' at an event, it's worth giving yourself the safety net of Raw in case you don't get the shot quite right (that's not an excuse to get sloppy with in-camera exposure though!).
JPEG: Running out of space on the card? JPEG's take up much less card room, so allow you to take many more shots. Take a look at how the number of remaining shots on your camera jumps when you switch from Raw to JPEG.
JPEG's also save to the card quicker than Raw files, being smaller. So if your camera's buffer cannot handle the continous burst shooting you are doing, switch over to JPEG. This can be useful for sports and wildlife photography.
Uploading image files to the internet requires compressing them so they are a manageable size. For this purpose, JPEG is a great file type. Similarly, storing personal images on your computer (i.e. family, friends, daily life etc) - the kinds of images that you might order as small 6x4 prints - is often best done in JPEG format. Keeping thousands of large Raw files can take up a lot of space!
So, I hope this has cleared up the main facts about the Raw file format for you. It all boils down to some very simple points really:
a) JPEG's are small files that save time and space and look pretty good right off the bat, but also afford us less control over processing.
b) Raw files are large and take up lots of space, but they have huge bit depth and dynamic range, enabling us to fine tune them in processing to perfection.
Raw vs JPEG is basically a choice between: speed, space and basic in-camera processing vs less speed, less space and powerful processing with an application like Adobe Camera Raw.