UNDERSTANDING DIGITAL EXPOSURE:

Part 1: Exposure Reduction for Highlight Retention
Part 2: Digital Exposure & Noise
Part 3: When Blocked-up Shadows Aren’t Really
Part 4: Take a Balanced Approach to White Balance
Part 5: Dynamic Range
Part 6: Extending the Tonal Range
Part 7: What’s the Real Difference Between RAW and JPEG?

GENERAL:

1) COST-EFFECTIVE PHOTOGRAPHY
2) CONTROL THE RANGE OF FOCUS
3) IMAGE INTERPOLATION
4) LOSE THE DEAD SHOTS
5) SCANNING 35MM FILM
6) THE RAW vs. JPEG DEBATE…
7) IS PHOTOGRAPHY EASY?
8) MUST EVERYTHING HAVE AN ADOBE SLANT?
9) A CAMERA TO PAINT WITH
10) WHAT'S THIS COMPOSITION THING ABOUT?

Understanding Digital Exposure

7. WHAT'S the REAL DIFFERENCE BETWEEN RAW and JPEG?

Every now and then on a forum someone will ask, “What’s the real difference between RAW and JPEG?” What will we actually see in our images and prints? Is there always a clear visual advantage to shooting RAW all the time? Answering these questions isn’t that easy (unless you own a company that sells RAW conversion software).

There is a tangled mass of nonessential technical information related to this subject. A little of it is even interesting! But really, one of the amateur's biggest challenges, if not the biggest, is learning how to creatively use image-editing tools. If we shoot RAW we’ll start off by editing in conversion software. If we shoot JPEG we can load our shots into capable image-editing software that supports layers. Then we can see what needs to be done to selectively make the best use of the image’s content, tones and colour. (JPEGs and TIFFs can be edited in some RAW conversion software too.)

Personal decisions have to be made. Should we shoot RAW and edit the image fully in conversion software that applies edits globally? Some do, but it’s more likely that most images will benefit from further work in image-editing software like Elements or Paint Shop Pro. So edited RAW files may require extra processing steps for the very best results.

Whatever the case, every effort should be made to expose the image intelligently in the first place. Whether we're working on RAW files or JPEGs, major tonal adjustments are best avoided. The key elements of the scene should hold reasonable shadow detail and show no signs of damage to the highlights where it really matters most. Sometimes it’s best to sacrifice deeper shadow detail to make the best use of lighter tones.

Proper digital exposure (not necessarily the same as with film) may produce an image that won’t look quite right until it’s edited in software. As mentioned here previously, the highlights are usually key. If they’re blown the image will usually suffer. Cameras can be set up to produce saturated, sharp JPEGs with good contrast that will need little or no work in software. But this can set unrealistic limits on the benefits of image-editing. It’s a fact that there are amateurs and pros who are happy to shoot JPEGs most of the time for their best work. Their images are impressive.

Assuming then a digital image is properly exposed, what’s the actual difference between RAW and JPEG? It largely depends on how much manipulation is needed, and where it's applied. High quality JPEGs are a visual compromise. Data is stripped away because generally our eyes don’t need it. High resolution well-exposed JPEGs can be tonally impressive. But the problems can arise during prolonged and targeted editing when the compressed data will start to show the strain.

Creating B&W images from channel-separated JPEGs is a good example. Individual colour channels may show random blotches associated with in-camera colour interpolation and JPEG compression. For top results from JPEGs it’s best to use a low ISO setting and not get carried away with sharpening, colour and contrast values. It’s generally good practice to shoot at the lowest ISO setting possible*, especially if you’re using a compact camera when your technique needs to be very good indeed.

JPGs have useful potential. Here the shadow detail was selectively edited to improve the dynamic range of the print.

Prolonged editing (within reason) is unlikely to a problem with most RAW files because, unlike a JPEG, the data has not been processed and effectively reduced in-camera. RAW files are more robust because there’s more information to work with. That’s why exposure is generally more crucial when shooting JPEGs. The more off the mark tonal capture is the more work will be needed in software. So it’s likely the image will start to visually break down.

DSLR JPEGs edited in a layered format (preferable) or as a TIFF (also preferable) are remarkably flexible in the shadow areas (especially full-frame DSLRs). However, smooth areas of blending tones will show signs of damage when processed too much—and it might not take a lot of manipulation before it happens. (It's worth remembering that not everything can be noticed at typical viewing distances.)

In the images below extreme editing has magnified the limitations of JPEG files. The RAW file has clearly suffered less damage where the tone is smooth, but has lost detail in the petals.

It's these more sensitive areas lacking in detail that can easily show the inherent weaknesses of JPEG compression. If they are well-exposed we probably won’t need to significantly adjust their tonal values with Curves or Levels. Although slight damage can be subtly smoothed away, it’s best if a JPEG's smoother tones are left well alone.

RAW can be very useful for getting some extra detail from the highlights. But the comparision below shows how little benefit there can be. In some contexts it's useful, but does it really matter in this example?

(Converted to best quality JPG.)

So why shoot JPEGs at all? Good question!

A very good grasp of well-equipped image-editing software means a lot can be accomplished with DSLR JPEG images, particularly if they’re shot at lower ISO settings. As mentioned, converting from RAW involves extra steps in software processes, whereas a properly exposed JPEG can be brought directly into image-editing software and manipulated for quality prints and DVD slideshows. And of course, even large megapixel hi-res JPEGs take up a lot less space everywhere, although for most this isn’t the problem it once was.

Actually, it may be a good idea to intelligently make the best of both file types. Some situations clearly cry out for RAW because RAW files will withstand the more intense editing that’s required. For example, an image with a really heavy colour cast can be balanced pretty well if shot in RAW but will almost certainly have to be binned if it’s a JPEG.

Long exposures may produce the best results when shot in RAW. Very misty landscape shots packed with subtle shades, tones and indistinct details will benefit from RAW capture, especially if several editing processes are essential. It also makes sense to use RAW when shooting indoor concerts. Indoor flash shots in a confined space may be adversely affected by the colour of walls, ceilings, electric light and furnishings. This may need correction.

Many amateurs are shooting RAW simply because they’ve been led to believe that it’s the only path to quality, regardless of the context, subject or general shooting requirements. But this isn’t the case. JPEGs produce excellent results when they are properly exposed, and sensibly edited and viewed.

Personal Note

As a dedicated amateur (that context can be important!) I prefer to routinely shoot hi-res JPEGs. But my DSLR is usually set to record RAW at the same time. I find that in practice JPEGs are frequently more than good enough for quality prints. But having RAW versions available means I can make use of the extra data on those occasions when I actually need it. A lot depends on the image itself, exposure choices, shooting conditions and what manipulation is envisioned.

It helps me a lot to be very familiar with powerful image-editing software, in particular its fundamental set of tools (I use Corel PHOTO-PAINT X4).

* Some cameras offer ISO 50, but there's no such thing. The DSLR design threshold for exposure is actually ISO 100. ISO 50 is really ISO 100 with a bit of in-camera manipulation that some claim marginally helps to suppress noise. But according to the manufacturer there’s about 1 stop less dynamic range in the highlights at ISO 50. Typically, the last thing we want to do is aggravate a sensor's inherent highlight limitations. But this contrived ISO speed comes into its own when shooting wide apertures in bright conditions or with flash. It's also a bit like a ND filter that restricts light allowing for longer exposures and shallower depth of field.

home | Personal Pages