What are RAW Images
A digital camera takes the information from the sensor and converts that information into a JPEG image using the in-camera settings for such things as white balance, brightness, contrast and sharpness. Those settings are either selected by the photographer or are automatically selected. Digital SLR cameras offer the option of saving the information that comes off the image sensor and save it directly to the memory card before conversion to a JPEG file. Such an file is referred to as a RAW Image file. If you choose to save your images as only JPEG, then the internal workings of the camera will take all that data from the sensor, process it, and save the file as JPEG. But a JPEG only haves 256 levels of brightness for each of the three RGB color channels (red, green and blue). On the other hand the RAW image has 4096 levels of brightness for each color channel, so if you save only as JPEG you camera will throw away some information.
Unlike RGB files such as JPEG and TIFF files, there is no standard for RAW images and each camera has it’s own format. Even within one manufacturer there are differences between camera models. The RAW image contains information from the camera’s sensor plus other information such as white balance setting, exposure, sharpening settings, and any other in camera color adjustment settings. Exif data is also stored in the RAW image.
Do RAW Images Lack Punch?
As digital cameras started to proliferate, we saw many of the camera manufactures build in their camera to digitally add more punch to the JPEG images. Although this started back in the days of film, it was the movement to digital that allowed for much more in camera processing. This is fine when the output in a JPEG where the camera can do the processing of the data off of the sensor.
With many cameras, when you shoot in RAW you can set the color adjustments in the camera. These do not actually change the colors inside the raw image, but the camera setting is recorded there. When you use the software that is sold by the camera manufacture, it will read what you set in camera and apply an equivalent of these settings to the RAW image. Then when you create a JPEG from the RAW image it will look similar to what the camera would have produced a JPEG itself.
It may help to think of RAW image files as a digital negative. With a film negative you have all the information as recorded by the camera but they are not viewable directly but need to be processed before viewing or printing. So it is with RAW images, they need to be processed before you can view or print them. That process involves converting them to a RGB file such as JPEG or TIFF.
When a film photographer makes a print from their negative they would never think about throwing away their film negatives because those negatives contain information that is lost in making the print. Likewise the digital photographer would not want to discard their RAW images after converting them to a RGB file format such as JPEG.
Advantages of Shooting RAW Images
When taking the picture if only a RAW image is recorded, that file needs to be processed before using it. That is typically done on a computer using software that can read the RAW image and write a JPEG file. That would normally require an extra step for the photographer and for that reason many photographers just set their digital SLR cameras to record JPEG only. However capturing the RAW image has many advantages compared with saving only a JPEG image.
- Higher image quality. Just as a film negative has more information that is contained in a print, a RAW image has more information that can be contained in a JPEG file.
- More effective post processing. Using a computer program to convert a RAW image to a RGB file allows much better control over changing parameters such as white balance, contrast, brightness, sharpening.
- Non-destructive edits. When you use a computer program to edit a RAW image you do not lose any of the original information. Any edits are stored either as data within the RAW image file (usually only if you are using software provided from the camera manufactuer) or in a sidecar file (as is done with Adobe products). Even if you crop the image, you can always go back to the RAW image and start over. If you crop a JPEG file, then the cropped area is lost forever.
- You can use a lossless compression, or no compression, for the RAW image file. JPEG files use a lossy compression, which means some information is lost each time the file is edited and re-compressed
Disadvantages of Shooting RAW Images
- Increased image size. RAW image file are usually 2-4 times larger than the JPEG file, or even more if their do not use any compression. Than means fewer images can be stored on a memory card and more hard disk space is used to store the images.
- No standard. There is no standard for RAW image formats. I have both a Nikon D70 and a Nikon D300 digial SLR and both cameras use a different RAW image. So any software that is used to convert the image needs to be able to process a particular RAW image. Adobe has proposed a standard RAW format they call DNG for Digital Negative. So far the big manufacturers have not adopted it.
- Post processing required. There is an increased time to process the image to a JPEG format that can be uploaded to a website or printed. However that is not as significant as it once was. With the great adoption of RAW image formats, you can now effectively use them directly. On a Mac computer you can view the images directly using the file browser (finder) and Windows offers add ins that can do the same. I can upload RAW images to my photo sharing site, Smugmug. The upload process does all the work to convert the RAW Image to a JPEG format for me. I use Adobe Lightroom and can export directly from there to SmugMug, having all the post processing applied to the RAW image before it is uploaded in a JPEG format.
Shooting RAW + JPEG
Many cameras offer the option to shoot both RAW and JPEG files at the same time so for each shot you get two images. This might sound like the best of all worlds. There are some disadvantages however. Two images will take even more space on the memory card. For my Nikon D300 camera the RAW image takes up about 13 mb using lossless compression and a JPEG Fine image takes up about 7 mb, so if I shoot RAW+JPEG Fine, each shot takes up about 20 Mb on the memory card and on the computer when transfered there. With the greatly lower prices on memory cards that is not as big of an issue as it once was.
There is also the added confusion of file management when you have two different files of the same image. If you rename the JPEG file and not the RAW file it is difficult to keep track of things. Some programs such as Adobe Lightroom do a very good job or recognizing that there is both a RAW image and a JPEG image with the same name, except different extensions, and shields you from the complexity of having two images.
So in conclusion I feel it is important to shoot all your pictures using the RAW Image format if your camera offers that option. Whether you take the extra step of shooting in plus JPEG, is a personal decision. If I had plenty of free disk space and was using a program such as Adobe Lightroom, I would probably shoot in RAW+Fine JPEG. There was a time I would shoot RAW + JPEG basic so I could upload the JPEGS to a website but that is not needed now since I can upload directly from the RAW images. If I was either lacking disk space or was using a photo library program that showed duplicate images with the potential confusion of handling both RAW and JPEG, I would shoot in RAW only and create JPEG files if I need to, such as doing online printing. What I would not recommend is shooting JPEG only. I don’t see sufficient advantages to compensate for the disadvantages.