multipliers | Strolls with my Dog

Absolute Raw Data

In the previous article we determined that the three $r_{_L}g_{_L}b_{_L}$ values recorded in the raw data in the center of the image plane in units of Data Numbers per pixel – by a digital camera and lens as a function of absolute spectral radiance $L(\lambda)$ at the lens – can be estimated as follows:

(1) $\begin{equation*} r_{_L}g_{_L}b_{_L} =\frac{\pi p^2 t}{4N^2} \int\limits_{380}^{780}L(\lambda) \odot SSF_{rgb}(\lambda) d\lambda \end{equation*}$

with subscript $_L$ indicating absolute-referred units and $SSF_{rgb}$ the three system Spectral Sensitivity Functions. In this series of articles $\odot$ is wavelength by wavelength multiplication (what happens to the spectrum of light as it progresses through the imaging system) and the integral just means the area under each of the three resulting curves (integration is what the pixels do during exposure). Together they represent an inner or dot product. All variables in front of the integral were previously described and can be considered constant for a given photographic setup. Continue reading Connecting Photographic Raw Data to Tristimulus Color Science →

The Raspberry Pi Foundation recently released an interchangeable lens camera module based on the Sony IMX477, a 1/2.3″ back side illuminated sensor with 3040×4056 pixels of 1.55um pitch. In this somewhat technical article we will unpack the 12-bit raw still data that it produces and render it in a convenient color space.

still life raw capture data file raspberry pi high quality hq cam f/8 1/2s base analog gain iso adobe rgb — Figure 1. 12-bit raw capture by Raspberry Pi High Quality Camera with 16 mm kit lens at f/8, 1/2 s, base ISO. The image was loaded into Matlab and rendered Half Height Nearest Neighbor in the Adobe RGB color space with a touch of local contrast and sharpening. Click on it to see it in its own tab and view it at 100% magnification. If your browser is not color managed you may not see colors properly.

Continue reading Opening Raspberry Pi High Quality Camera Raw Files →

Musings about Photography