What are the basic low level steps involved in raw file conversion? In this article I will discuss what happens under the hood of digital camera raw converters in order to turn raw file data into a viewable image, a process sometimes referred to as ‘rendering’. We will use the following raw capture by a Nikon D610 to show how image information is transformed at every step along the way:
In this and the previous article I discuss how Modulation Transfer Functions (MTF) obtained from the raw data of each of a Bayer CFA color channel can be combined to provide a meaningful composite MTF curve for the imaging system as a whole.
There are two ways that this can be accomplished: an input-referred approach (
) that reflects the performance of the hardware only; and an output-referred one (
) that also takes into consideration how the image will be displayed. Both are valid and differences are typically minor, though the weights of the latter are scene, camera/lens, illuminant dependent – while the former are not. Therefore my recommendation in this context is to stick with input-referred weights when comparing cameras and lenses.1 Continue reading COMBINING BAYER CFA MTF Curves – II