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Acquiring Images for Photoshop — JPEG vs. Raw [UP9]

Understanding Photoshop is a biweekly column that takes an in-depth look at how digital photographs are built and manipulated. It is a college-level course in plain English for free at Photofocus. To learn more see this article.

Don’t Skip Column 8

Shooting JPEG vs. Raw

Fig 03_04 MemoryWhen digital cameras became commercially available, the memory cards used to store pictures were very expensive. Many photographers couldn’t afford multiple or high-capacity cards, so they wanted more images to fit on a single, smaller card. Many users also emailed their pictures to friends and family. Small file sizes enabled consumers who lacked an understanding of digital imaging to attach photos to emails with minimum technical headaches. With these two scenarios in mind, manufacturers turned to an Internet-friendly format, JPEG (Joint Photographic Experts Group). It was a proven technology and one that was familiar to many users.

What is a JPEG File?

The JPEG format is extremely common because most hardware and software manufacturers have built support for it into their products. The JPEG format is also extremely efficient at compressing images, and it is a good format for continuous tone images, such as photos. A JPEG file looks for areas where pixel detail is repeated, such as the color blue in a photo of the sky. The file then discards repeated information and tells the computer to repeat certain color values or data to re-create the image.

Fig 03_05 LossyAThe JPEG Options dialog box is available when you modify or first save a JPEG file with Photoshop. When saving, you can adjust the Quality slider to reduce file size. It is best to leave Quality set to maximum if you will be making future edits to the image: This applies the least compression that could damage the images appearance.

Although JPEG is a good format for distributing images (due to their compatibility and small file size), it is not great for image acquisition or production. A JPEG file is lossy, meaning that every time you modify it in Photoshop and resave as a JPEG, additional compression is applied to the image. Over subsequent compressions, the image quality can noticeably deteriorate. This is similar to the act of making a photocopy of another photocopy: Additional image deterioration occurs with each processing step. The visible loss in image detail or accuracy is referred to as compression artifacts.

Fig 03_06 compare

Comparing JPEG to RAW

This image was captured as both a raw and a JPEG file when it was shot. The picture was taken with a Nikon D800, which can simultaneously write both files to the memory card when shooting. The raw file offers significantly greater latitude for post-processing and can recover more detail than the JPEG version. (You can download two more examples here and here).

So, if JPEG is inferior, why do so many people use it? Money and resistance to change are the simple answers. Its cheaper to shoot JPEG images because you don’t need to buy as many memory cards (however, the price of memory cards nowadays is so low that this is almost a moot argument). Certain scenarios like sports and photojournalism often rely on the speed associated with smaller files as well (but camera manufacturers are adding larger buffers in cameras to allow for high-speed raw shooting). Additionally, even many pros have been slow to abandon JPEGs due to fear of change. Learning how to use new technology requires time, something that many people are short of these days.

Newer digital cameras, generally the pro models, offer the ability to shoot raw (or native). The images are captured at a higher bit rate, which means that the pixels contain more information about the color values in the image. Most raw files have a bit depth of 10, 12, or even 16 bits per channel instead of the 8 used by JPEG. Raw formats also have a greater tonal range; hence, there is a better exposure for shadows and highlights. This extra information makes your work in Photoshop easier because it adds greater flexibility and control in image adjustments. You should have less work to do in Photoshop as well, because the image captured has more color information than a JPEG version.Camera Raw for TIFF and JPEG?

Although the Camera Raw interface can be used for JPEG and TIFF files, those images have already had the cameras processing permanently applied to the image. Shooting raw has many benefits and should be fully explored by reading the documentation that accompanies your camera.

Raw files can be four to ten times larger than JPEG files. This extra data is used to hold more image detail, which can reduce, or even eliminate, compression artifacts found in JPEG files. However, that extra data can increase the time it takes for the files to write to the memory card. As such, a memory card with a faster speed rating is a good investment and will help your camera keep up with the action you are shooting.

What is a Raw File?

The raw file captures the unprocessed data from the cameras image sensor. Although your camera may contain settings for sharpness, exposure, or lighting conditions, the raw file stores that setting as modifiable information and captures the original (unmodified) data that came through your cameras sensors. This is very useful because it lets you easily adjust white balance within Photoshop. Each manufacturer treats the format differently, using a proprietary format. Fortunately, Photoshop frequently updates its raw technology to support the newest cameras on the market. To find out if you can access a particular camera format from within Photoshop, visit Adobes Web site at www.adobe.com/products/photoshop/cameraraw.html.

Fig 03_07 Camera Raw window

Because the raw data is unprocessed, you must essentially develop the image data inside Photoshop. You’ll be presented with several choices when opening a raw image. You can choose to adjust several options related to the image, as well as the lens and lighting conditions. All the adjustments made in the Camera Raw dialog box are nondestructive, meaning the original image is preserved in pristine condition. You can tweak the image after shooting it, including being able to easily save those changes and apply them to similar exposures.

The Adobe Camera Raw dialog box is a versatile environment for developing your pictures. Try opening the file Overhang.RAW. Choose File > Open and navigate to the file you’ve downloaded. In Photoshop CS6 or later, you can even make localized adjustments by painting an area to select it and then use sliders to modify it.

The Camera Raw dialog box has continued to evolve since it was first introduced as a purchased add-on to Photoshop 7. Subsequent versions of Photoshop have updated the user interface. Fortunately, the Camera Raw dialog box is fairly intuitive, especially once you understand the concepts of adjusting images. We’ll cover this dialog box much more in later lessons.

Is DNG the New Raw?

In 2004 Adobe released the Digital Negative Specification (DNG) file format. The code and specifications were made publicly available so manufacturers could build support for the format into their products. The goal was to replace several proprietary raw file formats with a universal format. Despite initial optimism, camera manufacturers have been slow to adopt it (some even refusing). At this point, DNG files are a useful way to archive raw files and attach additional metadata. You can find out more about DNG by visiting Adobes Web site at www.adobe.com/products/dng/main.html.

To get occasional updates and digest emails concerning this series, you can join the Understanding Photoshop email list.

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