I like to know how things work. I ask “why” A LOT. Recently, I took an online course offered by lynda.com, one of the premier online learning environments. They cover many professions and subjects, including photography. One of their elite photography instructors is Ben Long, who has worked with clients such as 20th Century Fox and Bluenote Records. In this course, Learn Photography: Shooting in RAW Mode (sorry for capitalizing RAW, Ben), he covers all the details any nerd like me could possibly want about shooting raw images. It was so full of information, I went through it twice.
Frankly, most people would be bored with the depth of this subject, as there are few visuals and most of the videos involve Ben sitting at a desk and speaking, but I can honestly say that it was one of the best 1.5 hours I’ve invested in photography so far.
Here’s the kicker, right out of the gate: when shooting in raw, NONE of your camera settings, except those that control the amount of light hitting the sensor, have any impact on the final image you will produce. NONE of those fancy picture styles (Canon), HDR options or even white balance settings have any relevance. So spending a lot of time setting these up before you shoot might be a waste of time if you shoot in raw. There is one exception, outlined at the end of this piece.
In a nutshell, shooting in raw means that your final exported file will only have two types of information in it: how much light hit each photosite (which are light sensitive receptors arranged in a grid on the camera sensor) and what colour filter overlays that photosite (red, green or blue – RGB). Each photosite is physically covered by a colour filter, and the light that passes through it will be most intense in that colour wavelength. In this situation, your aperture, ISO and shutter speed selections do impact the amount of light hitting the sensor, and thereby, are relevant to the information in a raw file.
To really understand the implications of the above, you do have to understand how our eyes see light and colour, and how a digital sensor works. Ben explains these simply and cleanly. He also then explains how the camera records the information and the options you have once recorded. But most significantly, he explains the pros and cons of each option, including providing examples of situations any photographer might find themselves in.
The other bottom line: shooting in raw vs. shooting in JPEG is about more than just file size. That’s not something I learned in my training. When shooting in raw, all of the data captured by your camera is exported out when the file is exported (notwithstanding the option in some cameras to have “small” or “medium” raw files). When shooting in JPEG, several things happen:
- You are deciding that you will have the camera process the file before you export it; this is where the camera settings you select come into play. The white balance choice you made is applied, as is any picture style (contrast, colour palette, sharpness, etc.). Any special effects you selected (such as film quality looks) are also applied.
- You have the opportunity to perform other in-camera edits (where available), such as cropping.
- You make a choice about the final size of the file you wish to export, which tells the camera how much raw data to remove in order to achieve that compression result. It seems that when cameras compress files to produce JPEG images, the luminance or brightness captured by each photosite is not compressed, but the information about colour is. For every 64 photosites, large JPEG compression will average the colour across these sites and capture 1 data point. For smaller JPEG file sizes, even more is lost. And it is a permanent loss – there is no way to recover that original colour information later.
As an example of the pros and cons of shooting raw vs. JPEG, Ben explains that the camera works much harder to produce a JPEG, so if the photographer is in a situation where continuous shooting is required, the time to write a JPEG to the storage card may actually be longer than it would be with raw files, even if the stored file is ultimately smaller. Put another way, every image you shoot starts out as raw. When selecting JPEG in-camera as your storage option, you are simply deciding to process that raw data in-camera before storing it.
It seems the debate of raw vs. JPEG was most relevant when memory cards were smaller and when post-processing options on computers were much more limited. Today, any name-brand image processing software that can read raw data (Adobe Lightroom, Adobe Photoshop, Capture One, Photo Raw) is capable of handling the largest files efficiently. Workflows for raw files are similar, but with more options, to workflows for JPEG files. Instead of doing the processing in-camera, raw shooters elect to fully process their images on the computer, where better displays, more sophisticated software packages and frankly more time (since you are not trying to shoot while processing) are available.
There is one other big advantage to shooting raw and processing the resulting files on the computer. For technical reasons, the original raw files CAN NEVER BE ALTERED on the computer. Instead, any edits that are made to a file are saved as a separate set of instructions along side the file and are applied each time the file is opened. So, editing a raw file is truly non-destructive and can be reversed at any time.
So what’s the exception I referred to earlier? If you as a photographer are shooting raw but use the camera’s preview image feature as you are shooting, both the image and the associated histogram will be more accurately represented if you take the time to select settings that come close to what you desire in the final image. That’s because the preview image is a JPEG image. If you shoot tethered and/or don’t rely on the preview image, this isn’t a concern. That said, the histogram in-camera will never be the same as the histogram you will see when opening the raw file on your computer. So, ensure you always have a wide margin for error in things like highlight or shadow clipping when using the in-camera histogram.
And of course, once you process the image on your computer, exporting it to JPEG is often a preferred option for viewing or sharing. So eventually most images are compressed and will lose detail in that compression. But at least you’ll always have access to the full resolution image, with all of its adjustments, should you need it.
I always feel both tired and satisfied when I have an intellectual experience that makes me really think. You hit it out of the park on this one, Ben. Thanks.