dloow
Avslutat medlemskap
Jag har läst att de 256 nyanserna i en 8-bit bild (24 bit färgbild) inte är jämnt fördelade mellan svart och vitt. För att förklara detta visar författaren 2 olika exponeringsdiagram (ungefär såna diagram som finns under "kurvor" i PS). Det första diagrammet beskriver exponeringen med en linjär funktion. Nästa diagram innehåller en logaritmisk funktion. På y-axeln står det CCD Charge och på x-axeln står det EV.
Jag väljer att kopiera hans text. Jag förstår nämligen inte vad han menar.
"Here are two diagrams to illustrate what our sensor has just captured. They show the identical curve, but with the scene luminance mapped in two different ways: Linear scale is what the physical luminance really is, with a steadt increase of light. However, we like to think in terms of exposure, where each increasing EV is doubling the amount of light. This corresponds better to how we perceive light, and so the second diagram is in logarithmic scale.
What this tells us is that half of the avaliable values are taken by the brightest EV. The remaining half is divided between the second brightest EV and all the lower ones. If you do that repeatedly for a camera that captures 6 EVs total, and you try to represent them all with a total of 256 values, you end up with only two levels left for the EV containing the darkest shadow details. Most of the image ends up darker than we would see it, crunched together in fewer and fewer values. It's like cutting half off a birthday cake again and again, until only a tiny crumb is left for the party guest."
Sedan fortsätter han och berättar om gamma som kompenserar detta.
Kan någon förklara detta med andra ord, och helst på svenska....
Jag väljer att kopiera hans text. Jag förstår nämligen inte vad han menar.
"Here are two diagrams to illustrate what our sensor has just captured. They show the identical curve, but with the scene luminance mapped in two different ways: Linear scale is what the physical luminance really is, with a steadt increase of light. However, we like to think in terms of exposure, where each increasing EV is doubling the amount of light. This corresponds better to how we perceive light, and so the second diagram is in logarithmic scale.
What this tells us is that half of the avaliable values are taken by the brightest EV. The remaining half is divided between the second brightest EV and all the lower ones. If you do that repeatedly for a camera that captures 6 EVs total, and you try to represent them all with a total of 256 values, you end up with only two levels left for the EV containing the darkest shadow details. Most of the image ends up darker than we would see it, crunched together in fewer and fewer values. It's like cutting half off a birthday cake again and again, until only a tiny crumb is left for the party guest."
Sedan fortsätter han och berättar om gamma som kompenserar detta.
Kan någon förklara detta med andra ord, och helst på svenska....
