Raw vs JPEG For Photo Editing
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You may have noticed that I’ve been writing "raw" in small
letters and "JPEG" in caps, and there’s a reason for it. With most file
formats, the letters in the format’s name actually stand for something.
In this case, the term "JPEG" is short for Joint Photographic Experts
Group, the name of the organization that created the standard (just
like "GIF" stands for Graphics Interchange Format and "TIFF" is the
Tagged Image File Format). "Raw", on the other hand, doesn’t stand for
anything. It’s just a normal word, and what it means (in the case of
digital images at least) is that the file contains the raw image information that was captured by your camera’s sensor when you pressed the shutter button. What does that mean, and how is that different from JPEG? In many ways, shooting your photos as JPEGs is like sending a roll of film off to a photo lab to develop your images for you, and what you end up with is, well, whatever you end up with. When shooting JPEGs, your camera becomes the photo lab, processing the image in a series of steps that include setting the white balance, adjusting the contrast and color saturation, applying sharpening, and then compressing the image to reduce its file size (a process known as "lossy compression" because it results in a loss of image quality). Yes, you can edit and retouch the photo yourself afterwards in Photoshop, but you’re starting with an image that’s already been processed, with permanent changes already made to its pixels (and a lot of the original image information already discarded). Wouldn’t it be better if you could somehow grab the image information straight from the camera’s sensor before your camera’s little internal photo lab gets its high tech hands on it and makes decisions on what it thinks your photo should look like?
That’s where raw comes in. A raw file is like taking the original film negative into the dark room and developing the photo yourself, with complete control and creative freedom over the final result. In fact, raw files are often referred to as digital negatives, and we use a program like Adobe’s Camera Raw as a digital darkroom to process the raw files (many people use the terms "raw" and "Camera Raw" as if they’re the same thing, but "raw" refers specifically to the file type itself, while Camera Raw is an application created by Adobe that we can use to process raw files). Every bit of image information captured by your camera’s sensor is saved and stored in the raw file, with no processing of any kind. In fact, the files are so "raw" that we can’t even open them normally on a computer like we can with JPEGs and other file types. They can only be opened in a program like Camera Raw where we can then process the photos in any way we choose before opening them in Photoshop for further refinement or saving them out as a JPEGs or some other traditional file type.
The main benefit to capturing our images as raw files as opposed to JPEGs is that we have a lot more image information to work with, including a much wider dynamic range (the number of brightness levels in the image) and a larger color space, and this means we can push the images a lot further than we could with JPEGs, bringing out and rescuing hidden detail in the darkest shadows and brightest highlights, detail that often gets tossed away and lost forever by a camera’s JPEG conversion process.
To show you what I mean, let’s take a quick look at an example of how, just by working with raw files instead of JPEGs, we can get much better results with our images. Here, I’ve used Adobe Bridge (CS6, in this case) to navigate to a folder on my desktop containing two images. At first glance, just by looking at the thumbnails, it may seem like both images are the same, but there’s one important difference. The version on the left is a raw file and the one on the right is a JPEG file. The raw file has a ".CR2" extension at the end of its name, which is Canon’s raw file extension (other camera manufacturers use different extensions for their raw files) while the JPEG has a traditional ".jpg" extension:
A raw (left) and JPEG (right) version of the same photo.
Before I open these images in Camera Raw, we should first
look at another important difference between raw and JPEG files, and
that’s file size. All that extra image information
packed into raw files comes at a price, meaning the files themselves are
a lot bigger than what we normally see with JPEGs. I’ll select the raw
version of the image on the left by clicking on its thumbnail:
Selecting the raw file in Adobe Bridge.
With the raw file selected, if we look at its metadata over in the Metadata
panel in the right column of Bridge, we see that the pixel dimensions
of the image are 3744 x 5616, and the file size is a whopping 26.84 MB.
That may not seem "whopping" compared with, say, a 50 GB Blu-ray disc,
but compared to a JPEG file as we’ll see in a moment, it’s huge:
The Metadata panel showing, among other things, the size of the image in both pixels and megabytes (MB).
Next, I’ll click on the JPEG version of the photo to select it:
Switching to the JPEG file.
The Metadata panel in Bridge now shows us the same
information but this time for the JPEG file, and here we see that the
JPEG version has the exact same pixel dimensions (3744 x 5616) as the
raw file. And yet, the size of the JPEG version on disc is only 2.88 MB, nearly a tenth the size of the raw file:
The JPEG version is the same size, in pixels, but takes up much less space on the hard drive.
Of course, the file sizes of your own images may be
different and will depend largely on the megapixel (MP) count of your
camera, but one thing that won’t change is that a raw file will always
be significantly larger than the same image saved as a JPEG. Is this a
big deal? Not so much when you’re processing the image on your computer.
These days, Photoshop can easily handle a 20-30 MB file, and computer
hard drives are big enough and cheap enough now that running out of
storage space usually isn’t an issue. Where the extra size can pose a
problem, though, is when you’re out shooting your images. Raw files take
up much more space on your camera’s memory card, which means the card
will hold fewer photos than if you were shooting in JPEG. Also, if
you’re an action or sports photographer needing to fire off as many
shots per second as you can, shooting in raw can slow you down since it
takes your camera longer to save these larger raw files to the memory
card. For most of us, though, the increased image quality and editing
potential of raw images far outweigh any concerns about the file size,
so let’s open these two images in Camera Raw and see how much of a
difference there is.Photoshop actually lets us open and edit not only raw files but also JPEG and TIFF files in Camera Raw, so I’ll open both of these images by first clicking on the image on the left to select it, then holding down the Shift key on my keyboard and clicking the image on the right. This selects both images at once in Bridge (both are highlighted):
Selecting both photos at once.
With both photos selected, I’ll open them in Camera Raw by clicking the Open In Camera Raw icon at the top of the screen:
Clicking the Open in Camera Raw icon.
This launches the Camera Raw dialog box, with the raw
version of the image open in the large preview area in the center. We
can only view one image at a time in Camera Raw, but we can see both of
the images I’ve opened displayed as thumbnails in a filmstrip view along
the left. The highlighted image is the one that’s currently active:
The Camera Raw dialog box displaying the raw version of the image.
I’ll click on the JPEG version’s thumbnail on the left to
switch to it, and now we can see the JPEG version of the image in the
center preview area. So far, both the raw and JPEG versions look very
similar. And by “similar”, I mean they both look overexposed:
Switching over to the JPEG version by clicking on its thumbnail on the left.
In the upper right corner of the Camera Raw dialog box is the histogram
which shows us the current tonal range of our image, starting with pure
black on the far left and gradually increasing in brightness to pure
white on the far right. The higher the bars appear in a certain area of
the histogram, the more information we have in that brightness region of
the image. Here’s what the current histograms look like, with the raw
version’s on the left and the JPEG’s on the right. Just as with the
images themselves, they look nearly identical, with most of the detail
concentrated in the highlights as we’d expect to see with overexposed
images:
The histograms are not showing much difference yet between the raw (left) and JPEG (right) versions.
From what we’ve seen so far, it would be hard to justify
the increased size of the raw file when it looks no better than the
JPEG, but that’s about to change. I’m going to switch back over to the
raw version of the image by clicking on its thumbnail on the left:
Clicking the raw version’s thumbnail.
Now, this isn’t meant to be a detailed tutorial on how to
process images in Camera Raw, but a quick thing we can do is let Camera
Raw itself take its best guess on how to improve an image. If you look
below the histogram in the right column of the dialog box, you’ll see
that by default, Camera Raw opens the Basics panel
which is where we find most of the controls we need for adjusting the
white balance, exposure, contrast, and color saturation of the overall
image. Rather than dragging sliders and making changes to these controls
myself, I’m going to let Camera Raw try to correct the image for me by
simply clicking the Auto button directly above the Exposure slider. Once again, I’m working on the raw version of the image:
Clicking the Auto button in the Basics panel.
Here’s what Camera Raw came up with. The important area to
pay attention to here is the sky, as well as the snowy mountain top. A
moment ago this area appeared washed out and uninteresting, yet now,
with the raw version of the image, we see lots of great detail in the
highlights. Raw files contain so much image information that often
times, areas that appeared completely blown out at first actually
contain plenty of detail we can rescue:
The raw version now looks much better, with lots of detail in the highlights.
Of course, the shadows are now looking too dark but for
our purposes here, I’m not going to worry about them. Let’s jump over to
the JPEG version. I’ll click on its thumbnail on the left to select it,
then just as I did with the raw file, I’ll simply click the Auto
button in the Basics panel on the right to let Camera Raw try to
correct the image for me. This time, things don’t work out nearly as
well and the difference between JPEG and raw becomes more obvious. The
highlights look a little better than they did originally, but not by
much and not nearly as impressive as the raw version. The reason is
because the JPEG file simply doesn’t contain enough image information.
Most of the detail in the highlights was lost in the JPEG conversion
process, and once it’s gone, it’s gone:
The JPEG version after clicking the Auto button.
Let’s take another look at the histograms, where we now see
a difference between them. Notice that the raw version’s histogram on
the left still looks nice and smooth after the edit. That means we still
have continuous tone throughout the image, with colors and brightness
levels transitioning smoothly from darker to lighter. The JPEG version
on the right, however, isn’t holding up as well. See that “comb” pattern
in the highlights on the right with gaps between brightness levels? The
gaps mean we now have little detail remaining in those brightness
regions of the image. In other words, by making the JPEG version look a
bit better, we’ve actually made it worse at the same time:
The JPEG version’s histogram on the right is now showing gaps of missing information in the highlights.
We can see this more clearly by zooming into the sky area
of each image. Here’s a closeup of the sky in the raw version, with
plenty of detail and smooth, continuous brightness transitions:
The raw version is looking good.
Compare that with a closeup of the same area in the JPEG
version. Not only does it still look overexposed, but remember those
gaps in the highlights in the histogram? If you look closely at the
clouds, you can actually see the problem. The missing detail in the
highlights has resulted in ugly, harsh transitions between brightness
levels, commonly known as "posterization". If I darkened the exposure
even more, the posterization would become even more apparent. No matter
what I do with this JPEG version, I’ll never get it to look as good as
the raw version:
Improving the exposure of the JPEG version brought out big problems in the highlights.
There are more advantages to working with raw files over
JPEGs than what I covered here, and of course there’s lots more to
processing images in Camera Raw than simply clicking Auto. I’ll be
covering everything you need to know about working with Camera Raw in
this series of tutorials, but I hope for now I at least gave you an idea
of how much more potential there is for editing and retouching images
when you make the switch from JPEG to capturing and editing your images
in raw.
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