Context: The noise-based speed is defined as the exposure that will lead to a given signal-to-noise ratio on individual pixels. Two ratios are used, the 40:1 ("excellent image quality") and the 10:1 ("acceptable image quality") ratio. These ratios have been subjectively determined based on a resolution of 70 pixels per cm (178 DPI) when viewed at 25 cm (9.8 inch) distance. The signal-to-noise ratio is defined as the standard deviation of a weighted average of the luminance and color of individual pixels. The noise-based speed is mostly determined by the properties of the sensor and somewhat affected by the noise in the electronic gain and AD converter.

Question: Which ratios are employed to calculate noise-based speed?
Answer: the 40:1 ("excellent image quality") and the 10:1 ("acceptable image quality") ratio

Question: What is the noise-based speed?
Answer: the exposure that will lead to a given signal-to-noise ratio on individual pixels

Question: How are the two ratios found?
Answer: subjectively determined based on a resolution of 70 pixels per cm (178 DPI) when viewed at 25 cm (9.8 inch) distance

Question: What is a definition of signal-to-noise ratio?
Answer: the standard deviation of a weighted average of the luminance and color of individual pixels

Question: What factors influence the noise-based speed?
Answer: the properties of the sensor and somewhat affected by the noise in the electronic gain and AD converter

Question: Which ratio was subjectively determined?
Answer: Unanswerable

Question: What are the individual pixels defined by?
Answer: Unanswerable

Question: What is the signal-to-noise ration?
Answer: Unanswerable

Question: How many pixels are in a 40:1 ratio image?
Answer: Unanswerable

Question: The weighted average of the luminance and the noise in the electronic gain is defined as what?
Answer: Unanswerable