Lately—especially after our RED camera seminar and the entrance of 3cP into the RED One and Panavision Genesis “market”—we’ve received a lot of questions about the claimed 11, 13, or 16 f-stop “capabilities” of certain cameras. Here is our point of view on this contentious subject.

We’re really talking about two separate definitions: Observable Dynamic Range/Latitude and Potential Dynamic Range/Latitude.

Observable Dynamic Range/Latitude (ODR) is what the human eye can see in “spotting” mode when the angle of vision is no greater than 90°, and the observable field of vision is much brighter than the surrounding environment (like a film screen or computer/TV monitor in a darkened room).

In this kind of environment we can see no more than 4.5-5.5 T-stops, which must reflect / include all the variations in our surroundings, which may reach a contrast range of up to 1:2,000,000 contrast range (a landscape with a sun in the frame, or 1:100,00 in a case of a room interior against a daytime window without a fill light).

The physiology of vision in this environment is very different from our vision of nature, when our eye is in scanning and adaptable mode and we are able to perceive very high contrast images in full detail.

Please reference this densitometric measurement of an actual sensitogram of positive (print) film.

Negative film can see around 7 T-stops (see the sensitiogram of the negative film with related markings (white, grey, black, etc ) below. Also it will be helpful for an understanding of the problem to view the combined negative film / positive film curves which result when the negative film is printed onto the positive film for viewing.

Figure 1 - Negative film example:

Figure 2 - Postive film example:

Figure 3 - Combination of the Negative and Positive Curve

(How to reproduce the correct psychological “feeling” of this contrast range inside of the available 5.5 -7 f-stops is a different question and belongs to different discussion, but it was done successfully by many generations of experienced cinematographers and this process continues today.)

Potential Dynamic Range/Latitude (PDR) is what a digital camera can register, but the human eye cannot see it fully due to the limitation of the "spotting" mode of vision.

The best light sensitive digital chips today can be no more than 16-bit depth luminance which can be equated with Potential Latitude/Dynamic Range of no more than 16 T-stops, which cannot be directly perceived by the human eye on the screen, but can be seen only due to "second pass exposure manipulations" similar to "dodging/burning" and other altering and enhancing techniques typically done during the grading process.

But Potential Dynamic Range/Latitude (PDR) can be an important characteristic of the camera/digital light-sensitive element, providing that at least: cameras/digital light-sensitive elements are tested under identical illuminance and optical conditions: 18% (D(r)=0.74) neutral gray reflectance chip represented as .35-.33 mV; and reproduction curve of 5 neutral gray reflectance chips with reflectance of 4.5%, 9%, 18%, 36%, and 72% representing a straight line.

In our opinion, measuring these dual indexes—Observable Dynamic Range/Latitude (ODR) and Potential Dynamic Range/Latitude (PDR)—for each digital camera will satisfy both segments of our industry: practical working cinematographers and R&D enterprises and camera manufacturers.

Starting March 15—when we will release for sale version 3.1 of 3cP for RED Cameras—G&D will start to apply those indexes to all cameras for which 3cP has a “pre-fabricated” digital cinematography workflow, starting with the Panavision Genesis and RED One. Indexing of other cameras will follow, per cinematographer’s and manufacturer’s requests.

Yuri Neyman, ASC