Gain calculating device

Abstract

A more preferable WB gain is calculated during strobe illuminated photography. When a WB gain for an image captured through strobe illuminated photography is calculated, the degree of contribution of strobe light is first estimated. When the degree of contribution is estimated, the image is first divided into a plurality of blocks, and typical brightness values and typical color values of the respective blocks are determined (S 23 ). Subsequently, the highest-brightness block among the blocks analogous to the color of strobe light is identified as a strobe color block (S 26 ). When there is a strobe color block, the degree of contribution of strobe light is estimated on the basis of the position of the strobe color block, a difference between the brightness of the strobe color block and the brightnesses of other blocks, and the like (S 32 to S 48 ). Meanwhile, when there is no strobe color block, the degree of contribution is estimated on the basis of the position of the highest-brightness block having the highest typical brightness value among the plurality of blocks (S 28 , S 30 ).

1 . A gain calculating device for calculating a white balance gain at least for an image captured through strobe illuminated photography, the device comprising:
 a block dividing unit for dividing the image captured through strobe illuminated photography into a plurality of blocks;   an identification unit for identifying, from among the divided blocks, a highly-influenced block, which is a block presumed to have been greatly influenced by strobe light;   a first estimation unit for estimating, as a degree of first contribution, a degree of contribution of strobe light on the basis of at least one of the position of the highly-influenced block and a difference between brightness of the highly-influenced block and brightness of other blocks; and   a gain calculating unit for calculating a white balance gain from at least the degree of first contribution.   
   
   
       2 . The gain calculating device according to  claim 1 , wherein the block dividing unit divides an image captured through strobe illuminated photography into a plurality of blocks and calculates typical values of brightness of the respective divided blocks as typical brightness values; and
 the identification unit identifies, as a highly-influenced block, a block having a large typical brightness value among the divided blocks.   
   
   
       3 . The gain calculating device according to  claim 1 , wherein the block dividing unit divides an image captured through strobe illuminated photography into a plurality of blocks and calculates typical values of color values of the respective divided blocks as typical color values; and
 the identification unit identifies, as a highly-influenced block, a block having a typical color value close to the color of strobe light among the blocks.   
   
   
       4 . The gain calculating device according to  claim 3 , wherein the block dividing unit calculates typical values of brightness of the respective divided blocks as typical brightness values; and
 the identification unit identifies, as a highly-influenced block, a block having a large typical brightness value among the blocks having typical color values close to the color of strobe light.   
   
   
       5 . The gain calculating device according to  claim 3  or  4 , wherein a first estimation unit estimates the degree of contribution of strobe light on the basis of at least a difference between a typical brightness value of a highly-influenced block and a typical brightness value of the highest-brightness block having a high typical brightness value among other blocks. 
   
   
       6 . The gain calculating device according to  claim 1 , wherein a first estimation unit estimates the degree of contribution of strobe light on the basis of at least the position of a highly-influenced block. 
   
   
       7 . The gain calculating device according to  claim 6 , wherein a first estimation unit calculates the degree of contribution of strobe light as a smaller value with increasing distance of the highly-influenced block from an area where a main subject is presumed to be present. 
   
   
       8 . The gain calculating device according to  claim 7 , wherein the area where a main subject is presumed to be present is one of in the vicinity of a center of an image or at an AF detection point designated by a user. 
   
   
       9 . The gain calculating device according to  claim 7  or  8 , wherein the size of the area where a main subject is presumed to be present is changed on the basis of at least one of a zooming factor and a distance to a subject. 
   
   
       10 . The gain calculating device according to  claim 1 , wherein a first estimation unit estimates the degree of contribution of strobe light on the basis of at least a difference between a typical brightness value of a highly-influenced block and a mean brightness value of a plurality of blocks estimated to be comparatively unexposed to strobe light. 
   
   
       11 . The gain calculating device according to  claim 10 , wherein the plurality of blocks estimated to be comparatively unexposed to strobe light correspond to either blocks located around the center of an image, blocks located around an AF detection point designated by a user, or blocks located around the highly-influenced block. 
   
   
       12 . The gain calculating device according to any one of  claims 1  through  11 , further comprising:
 a second estimation unit for estimating the degree of contribution of strobe light as the degree of second contribution on the basis of a distance to a subject; and   a gain calculating unit for calculating a white balance gain on the basis of at least the degree of first contribution and the degree of second contribution.   
   
   
       13 . The gain calculating device according to any one of  claims 1  through  12 , further comprising:
 a third estimation unit for estimating the degree of contribution of strobe light as the degree of third contribution on the basis of a difference between environment brightness achieved before firing of strobe light and environment brightness achieved at the time of firing of strobe light; and   gain calculating unit for calculating a white balance gain on the basis of at least the degree of first contribution and the degree of third contribution.   
   
   
       14 . A gain calculating device for calculating a white balance gain at least for an image captured through strobe illuminated photography, the device comprising:
 a first brightness acquisition unit for acquiring environment brightness achieved before firing of strobe light as prefiring brightness;   a second brightness acquisition unit for acquiring environment brightness achieved at the time of firing of strobe light as firing brightness;   an estimation unit for estimating, as the degree of third contribution, the degree of contribution of strobe light on the basis of a difference between the prefiring brightness and the firing brightness; and   a calculating unit for calculating a white balance gain on the basis of at least the degree of third contribution.   
   
   
       15 . The gain calculating device according to  claim 14 , wherein the first brightness acquisition unit acquires, as prefiring brightness, a mean brightness value of a preview image acquired before firing of strobe light.