Is there still a debate about JPEG vs raw? For anyone in this group, using the raw setting in your camera should be a no-brainer. Here’s why.
JPEG files are 8 bit and raw files are 14 bit (may vary, 12-16, depending on camera). Bits translate to tonal values, so an 8 bit file has 256 tonal steps from black to white while a 14 bit file has 16,348 steps.
This is important when manipulating images in Ps or Lr. For example if you are working on luminance and colour in a sky or trying to bring out detail in the dark areas of an image you are working with a limited range of those bits. With a JPEG you might be working with say one fifth of the total number of bits, just 50. So if you “push” those areas the images will show unsightly bands or break up into blocks with strange colours. In the case of the raw file you will be working with more than 3,000 bits and the transitions will be seamless to the eye.
In the 4X enlarged example below the camera was set to shoot JPEG + raw at 1/1250, f4, ISO 100. Both images were processed the same in Lr by clicking on Auto in the Basic panel and using the White Balance colour picker on the white coffee sign.
There was not enough data in the JPEG file to handle the “stretching” required so it broke up into ugly colour blotches. The raw file was able to handle the “stretch” and seamlessly revealed subtle tonal gradations in a very dark area of the image.
Why is this? Well, as already explained it has to do with the number of bits. More particularly, every digital imaging device makes a raw file, even cameras and old point and shoots that would only produce JPEGs. The camera has software built in that examines the raw file, makes adjustments to brightness, contrast, colour, saturation, sharpness and goodness know what else, then spits out the JPEG.
The JPEG image uses a subset of the raw data collected by the sensor, deletes what it didn’t use and then compresses the file down to 8 bits. So when you try to edit a JPEG your image editing program goes looking for extra data, can’t find it and the blocky artefacts are the result.
So, given that most of us spend as much money as we deem reasonable on a camera, the heart of which is the digital sensor, why would you then shoot JPEGs which chuck away 60-95% of the data gathered by that expensive miracle of a sensor?
The un-cropped images above show the final comparison between the straight out of camera JPEG and the processed raw file. This scene was chosen, not for its aesthetics, but for the extreme lighting conditions - a back lit black van.