Patent ID: 8780241

Claim:
A method for performing neutral density filtering in a digital camera having a pixel array including a plurality of pixels arranged in rows and columns, the method comprising: resetting the plurality of pixels in the pixel array; reading pixel values from the plurality of pixels in the pixel array with a delay relative to the resetting of the plurality of pixels, wherein the delay from the resetting to the reading of at least selected ones of the plurality of pixels is selected to implement a neutral density filtering operation and wherein the resetting of the plurality of pixels includes: resetting the pixels row by row across the pixel array with a variable timing such that an interval, t 1 , between the resetting and reading of respective rows of pixels at a first end of the array is less than an interval, t 2 , between the resetting and reading of respective rows of pixels at a second end of the array; resetting the rows of pixels between the first end of the array and a row X of the array with the interval t 1 between the resetting of each row of pixels and the reading of the respective row of pixels, where X and Y are integers and Y is greater than X; resetting the rows of pixels between a row Y of the array and the second end of the array with the interval t 2 between the resetting of each row of pixels and the reading of the respective row of pixels; and resetting rows of pixels between row X and row Y of the pixel array such that each successive row of pixels between row X and row Y has an increasing delay between the resetting and reading of the row, the increasing delay being greater than t 1 and less than t 2 ; and determining values for t 1 and t 2 including: capturing an image of a scene using the pixel array; analyzing pixel values at the first and second ends of the pixel array respectively to determine an image intensity gradient from the first end to the second end; and setting t 1 and t 2 to reduce the image intensity gradient.