Introducing RAW
In digital photography a RAW image file contains a direct data dump from the sensor without any processing performed on it (other than lossless compression). A JPEG image is a development of this RAW data. This is true even when you shoot in JPEG, except there the conversion is done by the camera. A RAW image is often called a digital negative, and the process of converting it to a normal image format (say jpeg) is called developing it.
Raw file advantages
Raw files have a number of advantages over jpeg:
- Many shooting parameters can be decided in post
- Lossless compression means you keep all your data
- More data to work with for PP due to greater bit depth
- Recover some highlights and shadows
Raw file disadvantages
- Larger file size
- More processing power required
- Images need to be converted before they can be used in programs or uploaded
- Introduces an extra step in your workflow
When to use RAW
Given how good Olympus cameras are at producing out-of-camera jpegs there's often no pressing reason to bother with RAW. That said, if you have a relatively fast computer system and don't mind a bit of extra hassle before yo uan send out your pictures, there's no real reason not to. In the end, in many cases it's a matter of personal preference.
In many cases, but not all. There are a couple of situations where RAW gives an undeniable benefit stemming from the ability of taking some decisions at a later time. I therefor recommend to use RAW or RAW+JPEG in those cases.
Uncertain lighting: white balance
White balance colour adjustments are done in the raw conversion phase. the actual white balance setting has no effect at all on the RAW image data. Sure, when you open the raw file you'll see the current setting applied, but this is just a single global value for the image (e.g. 4000K) that is taken as the default. On a pixel level, it is ignored.
This means that in cases where you are really unsure about the white balance and when other options do not suffice (usually due to mixed lighting conditions), your best option is shooting in RAW. This way you can make the white balance adjustment after the fact without using any image data. For this purpose, most RAW convertors will let you select a colour in the resulting image and designate this the neutral point. It will then adjust white balance accordingly. Even the most basic raw convertor will let you set the colour temperature.
Trying to do this with a jpeg will result in noise, posterization effects and colour casts as there is insufficient data to do the calculations to the same degree.
Uncertain lighting: dynamic range
When taking a picture as jpeg, the camera will select what is called a "curve" to your image. The curve controls what RAW values correspond to what luminosity values. The most visible effect of this is that both the highlight as the shadow clipping points are set. Anything brighter than the highlight clipping point will be white, everything darker than the shadow clipping point is black.
The curve also controls the contrast, especially near these clipping points. By default the contrast is greater in the midtones than at the extremes. If you are shooting a scene with high contrast, it's quite possible that you will get both highlight as shadow clipping in one image, or at least near-clipping. Shooting RAW you can often recover some of these clipped shades by adjusting the contrast near the clipping points (at the expense of contrast in the midtones).
In effect this gives you the power in post to apply the same techniques as used by shadow adjustment technology (called gradation: auto in olympus cameras) and more.
How to use RAW
While most image programs read jpeg on their own, RAW files require special programs called RAW convertors. Most high-end graphics programs include a raw convertor and there's many standalone programs out there, ranging in price from free to hundreds of euros. On top of that most camera manufacturers include a raw convertor of their own. Olympus Master and Olympus Studio mimic the camera's built-in convertor to such a degree that if you change none of the settings the resulting jpeg will be identical to what you would have gotten by shooting jpeg. Using other convertors will produce different results, since each one has a different opinion on how to interpret the raw data. It's best to try several raw convertors before settling on one, to make sure you get results you are pleased with.
To use RAW you will need to build an extra step into your imaging workflow: the raw conversion. This step is normally done directly after copying the image from your memory card. While the specific process of raw conversion differs from one program to the next, generally the following steps are part of it:
- Set or adjust white balance
- Sharpening
- Contrast adjustment
- Straightening
- Removing noise
While you could perform all these steps on the jpeg as well, the raw convertor has more data to work with and will thus induce fewer defects or artifacts. The defaults for the conversion will be the parameters set in your camera. and of course you don't need to override these if you are pleased with them.
Since there's such a wide variety in raw convertors I will not go into the process in detail here but will leave that for a future article.
ORF, DNG, RAW
A quick final point on formats. Every camera brand has its own RAW format. Within each brand every model is usually different as well. This means that by now there's dozens of different, mutually incompatible raw image formats. To complicate matters further, almost all these formats are proprietary, and undocumented, meaning that the makers of convertors have to guess and experiment to get the data out. Unfortunately Olympus's ORF is one of the more uncommon formats and thus not supported in all convertors.
To add a bit of standardization, Adobe introduced the Digitan Negative Graphic (DNG) format. Most raw formats can be converted to this unified raw format (without much or any loss of data) using Adobe's free utility. The DNG files can then be used instead of RAW files in a number of graphics programs.
