Retouching refers to the adjustments made to a photo after it is shot. With photos taken in JPEG, this can cause the image quality to deteriorate. However, will RAW images suffer the same fate? Find out more as I explain in this article. (Reported by: Ryosuke Takahashi)

Take special care when adjusting the brightness

Before RAW post-processing
 

After RAW post-processing
 

RAW post-processing was carried out using Canon’s Digital Photo Professional software, with the brightness set to EV-0.17, and the Picture Style changed from Auto to Landscape. However, particular care should be taken when adjusting the brightness to as to avoid ruining the picture.

RAW is a very convenient format for post-processing as various settings can be changed after shooting. In contrast, there are limits to the settings that can be adjusted for JPEG data. If you also take into account the deterioration in image quality that occurs, post-processing is almost impossible for JPEG.

However, excessive RAW post-processing may lead to a deterioration in picture quality. In particular, the effects of adjusting the brightness of a photo using exposure compensation and the tone curve cannot be ignored.

In principle, a DSLR allows for the optimal amount of light to hit the image sensor so as to achieve a desirable level of brightness and gradient in the image. Hence, if an extremely underexposed image is retouched as described above, the data will be damaged. Even if the brightness seems to be restored, you still get a noisy image. This is because various image information within the dark areas of the shot is not recorded properly. Taking a voice recording for example, it would be as if the sound source was recorded at a whisper. Hence, even if you increased the volume when playing it back, the resulting sound quality would be poor. It is similar to the phenomenon of a sound being hard to make out when it is not recorded at an appropriate sound pressure because background noise is captured together with the recording. Even with digital images, it is important to match the exposure to a reproducible range (dynamic range).

Differences between RAW and JPEG

There are benefits and drawbacks to shooting using RAW and JPEG. RAW is suited to scenes where you want to take your time and shoot carefully, while JPEG is preferable when you need to quickly take burst shots. Rather than sticking to one format, it’s a good idea to instead choose the best combination, depending on the scene and subject.
Furthermore, the image processing algorithm differs between the two, so be aware that a JPEG image produced from RAW will not be exactly the same as a JPEG image taken with a camera.

Data type: RAW

Benefits
- Large amount of information such as colour and gradient.
- Even old files can be post-processed with the latest software.
- Lets you achieve the particular finish desired.

Drawbacks
- Requires post-processing.
- Needs dedicated software to post-process.
- Large file size when recorded.
- Maximum number of shots is reduced.

Data type: JPEG

Benefits
- High degree of universality, and can be viewed in any browsing environment.
- Post-processing is not necessary. 
- Small file size when recorded.
- Large number of shots possible.

Drawbacks
- Small data capacity for colour and gradient.
- The image quality deteriorates in post-processing such as when retouching.
- Difficult to cover up mistakes in the shot.

 

Ryosuke Takahashi

Born in Aichi in 1960, Takahashi started his freelance career in 1987 after working with an advertising photo studio and a publishing house. Photographing for major magazines, he has travelled to many parts of the world from his bases in Japan and China.

 

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