Here's a short story:

Relatively insensitive film, with a correspondingly lower speed index, requires more exposure to light to produce the same image density as a more sensitive film, and is thus commonly termed a slow film. Highly sensitive films are correspondingly termed fast films. In both digital and film photography, the reduction of exposure corresponding to use of higher sensitivities generally leads to reduced image quality (via coarser film grain or higher image noise of other types). In short, the higher the sensitivity, the grainier the image will be. Ultimately sensitivity is limited by the quantum efficiency of the film or sensor. 

The Warnerke Standard Sensitometer consisted of a frame holding an opaque screen with an array of typically 25 numbered, gradually pigmented squares brought into contact with the photographic plate during a timed test exposure under a phosphorescent tablet excited before by the light of a burning Magnesium ribbon. The speed of the emulsion was then expressed in 'degrees' Warnerke (sometimes seen as Warn. or °W.) corresponding with the last number visible on the exposed plate after development and fixation. Each number represented an increase of 1/3 in speed, typical plate speeds were between 10° and 25° Warnerke at the time. (End of story)

Provide your best guess for the following question. Give ONLY the guess, no other words or explanation.

For example:

Guess: <most likely guess, as short as possible; not a complete sentence, just the guess!>

Here are a few examples of questions and answers:

Question: What is the speed of a insensitive film?
Guess: lower speed

Question: What does it require more of?
Guess: exposure to light

Question: What is another name for it?
Guess: slow film.

Question: What is a fast film?
Guess: no

Question: What is a sensitive film?
Guess: fast films

Question: So what happens if it has higher sensitivity?
Guess: reduced image quality

Question: How does that do to the image?
Guess: via coarser film grain or higher image noise of other types

Question: What causes the image to be grainier?
Guess: high sensitivity

Question: What is sensitivity limited by?
Guess: the quantum efficiency of the film or sensor.

Question: What did the Warnerke Standard Sensitometer consist of?
Guess: a frame

Now answer the following question in the same format.

Question: What else did it have?

an opaque screen with an array of typically 25 numbered, gradually pigmented squares