NormanBates said:
PVS said:
Why people mistake DR for exposure latitude?
I always thought they were the same. Care to explain the difference?
Dynamic range refers to the total maximum physical range of tonal levels a camera sensor is capable of recording. Exposure latitude refers to the ability of an actual exposure taken with a camera to be tuned or adjusted. A true RAW photo strait off the sensor is very dull, flat, lifeless, lacking a significant amount of contrast. When we import our RAW photos, most RAW editors apply a tone curve. Usually one of the manufacturer defaults (such as Camera Standard or Camera Neutral, etc.) These tone curves adjust how levels are allocated in the final image you see on your screen.
In a linear image, levels are distributed equally (hence the dull, lifeless, low-contrast appearance). With a tone curve applied, more levels are allocated to the shadows and the highlights, effectively "compressing" the wide dynamic range into a narrower contrast range. That brightens and adds life and color to an otherwise dull original exposure. The side effect of that is you have a lot of levels "bunched up" in the shadows and in the highlights around the roughly linear growth of the midtones. It's thanks to these tone curves that we have the ability to "recover" highlights and "lift" shadows.
Technically speaking, LetTheRightLensIn is correct...there is no such thing as highlight recovery or for that matter shadow lifting. Not with a true RAW image that has not yet had tone curves applied. But we generally don't work with our RAW photos in their true form. When it comes to the shape of tone curves, Nikon tends to allocate a lot more levels to the "foot of shadows" than Canon (and, for that matter, most other manufacturers, including MFD manufacturers.) They have more freedom to for sure, thanks to their lower read noise. That doesn't account for the ability to push shadows around by as much as 6 stops though...Exmor sensors only offer about 2 stops of additional DR in the shadows. Examining Nikon's tone curves indicates they allocate more levels to the shadows than their low read noise offers alone with their curves.
Similarly, Canon allocates more levels to the "shoulder of highlights" in their tone curves. They don't allocate as many more levels to highlights as Nikon seems to do to the shadows, however in Canon's newer cameras their highlight shoulder tends to be a little longer and fall off more into the highlight range than Nikon cameras. This is part of the reason you can overexpose by four stops with a modern Canon camera and still be able to recover (although its doubtful you could overexpose by 6 stops and still recover...Nikon still has around a 2-stop DR edge in the end.)
Exposure latitude is benefited by these tone curves, and the ability to recover highlights and shadows from "beyond the foot and shoulder." Exposure latitude is enabled by DR, and the more DR you have, the more you can tune those curves to allow greater and greater latitude.