Warning: If you’re not a camera geek, this post will bore you to tears. It’s aimed at those who might be on the fence about shooting in RAW format.
In January, I finally decided to go RAW. My camera lets me choose to capture digital photos as JPEGs, RAW files, or both, and I moved from shooting exclusively JPEGs to RAW files instead. JPEGs use a lossy compression scheme in which information is discarded as the original file is reduced in size. RAW image files, in contrast, contain the “raw data” from the camera’s sensor (more or less). RAW files hold additional information about lighting conditions and camera settings, and they represent each pixel’s color with much greater accuracy. A JPEG file stores 8 bits per color channel for each pixel. RAW images store 12-14 bits, allowing them to represent colors with 16 to 64 times greater fidelity.
That sounds pretty impressive — compelling, even — but there are lots of reasons to stick with JPEG. For starters, RAW files are huge compared to JPEGs. (RAW images from my camera are about 7x larger than the corresponding JPEGs.) Your hard drive will fill up much more quickly, as will your camera’s memory card and, since it takes longer for your camera to write RAW files to the memory card, you’ll have a longer wait between shots. Plus, you can’t view or print RAW files directly — you have to convert them to JPEGs before you can do anything with them! Why bother?
I liked the JPEGs produced by my camera, so I had always figured there was no reason to switch. I often make minor edits to the JPEGs after they’re imported to my computer though, and that requires saving a new JPEG file which will almost always be of lower quality than the original JPEG. I began to wonder if cropping photos, for example, was resulting in a visible loss of quality. RAW files need to be turned into JPEG images to be useful, but you can perform all of your edits on the high-quality image and then convert to JPEG just once when you’re finished. An experiment was called for…
During our Cornwall trip in January I had my camera store each shot in both JPEG and RAW so I could watch for differences. While I was initially interested in improvements in edited photos, the image quality in unedited pictures made a convert out of me. I’ll share some images that highlight the differences. The shots of the rope below are cropped out of a picture from the Maritime Museum in Falmouth. The JPEG created by my camera is on the left, and the JPEG produced from the RAW version is on the right. (Pixel peepers can click to open larger versions of each.) It was taken indoors without a flash, at ISO 800, f/2.2, and a shutter speed of 1/30th of a second.
The colors are more accurate in the photo on the right, and there’s a greater dynamic range — the white parts are still white, but more detail can be seen in the shaded areas. There’s a bit more noise (a speckle of dark pixels here and there), but overall I find the picture on the right to be a noticable improvement over the one on the left. They’re both JPEGs, but having the camera save the RAW image allows software on a laptop or desktop to do the conversion. (I used Apple’s Aperture software.) Lots more time and computing power can be brought to bear than when the JPEG is generated by the camera and, as I’ll mention below, there are more opportunities for producing good final versions from technically flawed shots.
Here’s another pair, again with the camera-produced JPEG on the left and the one stored as RAW and converted later via Aperture on the right. Neither is perfectly sharp, as I was taking it at full zoom and a relatively slow shutter speed (ISO 800, f/5.6, 1/20th), but the one on the right is much clearer and crisper, with better color once again.
One weakness of using Aperture to process RAW images is that it doesn’t do a very good job of dealing with noise — especially at higher ISO values. In Apple’s defense, it’s a hard problem. One needs to average out the color of neighboring pixels to help remove the “speckle”, but you don’t want to do so much averaging that you lose detail in the photo. The processor in my camera does quite a good job of turning noisy image data into good-looking JPEGs, as shown below. The photos are cropped out of a shot of Flora sleeping in the stroller on a train. It was taken in what little natural light there was (ISO 800, f/2, 1/25th of a second). The first shot is the JPEG produced by the camera, followed by the version Aperture produced from a RAW version of the photo. (Click the photos to see larger versions.)
Noise is readily visible, especially on large areas of consistent color like her cheek. Luckily, there are plug-ins for Aperture that do a much better job with noise. Here’s the RAW version processed by a plug-in called Noise Ninja. (The yellow line is there because I used a trial version of Noise Ninja.) It’s possible to tune the level of noise reduction, which can be handy. The noise is pretty well controlled in the version below, and there’s more detail in dark areas — around her ear, for example.
This last example is a photo taken the evening that Charlie broke his arm. It was taken in very low light (we had the lights turned down), at ISO 1250, f/2, and 1/20th of a second. My camera often gets the white balance wrong in very low light, as can be seen in the first photo. Adjusting the white balance on the RAW image is simple, and the resulting photo will be of better quality than a JPEG that’s been tweaked to improve white balance. The second photo looks better overall, but if you inspect the full-sized version you’ll see it has a lot of noise. It’s a challenging situation: High ISO, with faces in the scene, but at a distance that makes facial features quite small and easy to lose in the noise.
Here are cropped versions showing just Charlie’s face. (Click to see full-sized versions of the face shots.) First is the original shot, with incorrect white balance. The second has had the white balance corrected. Both of these were converted from RAW to JPEG by Aperture. The third is the corrected version after running it through Noise Ninja to reduce the visible noise. It’s still not perfect, but it’s much better than the original.
The full-sized version of the whole scene with noise correction applied is here. Now I just need to buy a few more memory cards and hard drives…