Image Compression: RAW + JPEG Shooting

One of the first things you need to decide when using a digital camera is whether to shoot in RAW or JPEG file format. Or so you might have thought. In fact, with most EOS digital cameras you don’t have to make that choice – you can shoot both simultaneously. All EOS digital cameras (except the EOS D30 and D60) can save both RAW and JPEG files to the CompactFlash card at the same time. And if your camera has card slots for CompactFlash and SecureDigital media, it is possible to save RAW files to one and JPEG files to the other at the same time.

Some photographers prefer to shoot RAW because of the extra flexibility this file format offers; others prefer to shoot JPEG because it means they don’t have to spend so much time on their computers afterwards. By shooting both RAW and JPEG together, you can get the best of both worlds – an image that you can tweak endlessly in RAW software, and one that you can print out straight away without the need for conversion on your computer.

The downside – and there is always a downside – is that saving both takes up valuable memory card space. This means you’ll be using more memory cards – and changing them more frequently.

Prints and E-mail

There might be times when you want to take photographs to e-mail, or for a website, but also need prints at a later date. Let’s say there is an event such as a wedding or anniversary, or the birth of a child. You might want to send a few of the images you have taken to friends and relations by e-mail without delay, but also make some quality prints later. Here, you can shoot with RAW+Small/Normal JPEG.

Safety Net

Even if you generally shoot only JPEGs, there are occasions when you might want to shoot RAW and JPEG simultaneously simply because you want back-up and peace of mind. If you have been asked to photograph a wedding, for example, you can shoot Large/Fine JPEG images to avoid a lot of post-processing work on a computer. However, if for any reason you need to tweak the contrast or exposure more than you are able to with your JPEG files, then you’ve got the RAW files as back-up. You can pick and choose the individual RAW files that you want to convert and work on.

Colour Cast

Imagine you are photographing a wedding. Inside the church you set the camera white balance to ‘Tungsten’ for available light shots of the service. Then you rush outside to start taking pictures of the couple as they came out of the church – but forget to reset the white balance to ‘Daylight’.

All the images have a strong blue colour cast (above left). If all the images were shot as JPEG files, you might be able to make some corrections to the files in Photoshop, but the colours will not be perfect. If you had shot a backup set of images as RAW files, the day would have been saved. Before each RAW file was converted, you would have been able to change the white balance from ‘Tungsten’ to ‘Daylight’ and the final prints would have shown correct colours (above right).

Tethered Computers and WiFi Networks

Capturing RAW and JPEG images together can be a real advantage if you are shooting tethered to a computer. The set-up allows you (and anybody else involved in the shoot) to check the images immediately on your computer’s much larger screen. However, downloading RAW files to your computer can be quite slow, especially if you are shooting in bursts.

Capturing RAW+JPEG gives you much more flexibility. You can download the JPEG files to your computer, while the RAW files stay on the CompactFlash card. Downloading JPEGs to your computer is much quicker than downloading RAW files, which means you don’t have to wait as long for the images to appear on the screen.

This is especially important if you are using one of the Canon WiFi units to transmit images wirelessly back to your computer. Although these wireless transmitters are able to transmit at up to 54mbps, in practice they can only transmit at the maximum speed of your network, which may be much slower if conditions are less than ideal. Sending large files across a wireless network is never lightning fast, so minimizing the size of the file you need to send will ensure the best network performance, while leaving the high-quality image files on your camera for working on later.