Calculating noise from multiple digital images having a common noise source

1. A method for estimating a noise characteristic value for a plurality of digital images that are affected by a common noise source, comprising the steps of:

a) receiving a plurality of source digital images that are affected by a common noise source, each source digital image including a plurality of pixels;

b) calculating a total number of pixels included in the source digital images;

c) receiving a predetermined target number of noise estimates to be calculated for the source digital images;

d) using the total number of pixels and the predetermined target number of noise estimates to calculate one or more pixel sampling parameters for the source digital images;

e) using the source digital images and the one or more pixel sampling parameters to calculate a predetermined number of noise estimates; and

f) using the noise estimates to calculate a noise characteristic value for the source digital images.

2. The method of claim 1 further including the steps of:

i) receiving the plurality of predetermined target number of noise estimates wherein each predetermined target number of noise estimates relates to a different average number of pixels per image;

ii) calculating an average number of pixels per image for the source digital images; and

iii) selecting one of the plurality of predetermined target number of noise estimates using the calculated average number of pixels per image for the source digital images.

3. The method of claim 1 wherein the one or more pixel sampling parameter is used to select pixels of interest for calculating the noise estimates uniformly throughout the source digital images.

4. The method of claim 1 wherein two pixel sampling parameters are calculated for the source digital images, the two pixel sampling parameters relating to different spatial orientations.

5. The method of claim 4 wherein the two pixel sampling parameters have different values.

6. The method of claim 1 wherein step d) includes calculating the noise characteristic values as a function of the numerical pixel values.

7. The method of claim 6 wherein step d) further includes the steps of:

i) assigning each noise estimate to one of a plurality of numerical sub-range intervals relating to different numerical ranges of pixel values;

ii) receiving a predetermined sub-interval target number of noise estimates; and

iii) after having calculated the predetermined target number of noise estimates using all of the source digital images calculating additional noise estimates corresponding to numerical sub-intervals which collected fewer than the target sub-interval number of noise estimates.

8. The method of claim 1 wherein the source digital images have pixels corresponding to different colors and step c) includes calculating the noise characteristic values as a function of the color of the source digital image pixels.

9. The method of claim 1 wherein the source digital images have pixels corresponding to different colors and step c) includes calculating the noise characteristic values as a function of the color and the numerical values of the source digital image pixels.

10. The method of claim 1 wherein the noise characteristic value is a function of the standard deviation of the noise present in the source digital images.

11. The method of claim 1 wherein step d) includes:

i) using a residual spatial filter to calculate pixel values for a residual digital image for each source digital image;

ii) using the pixel values of the residual digital images to generate a residual histogram; and

iii) using the residual histogram to calculate the noise characteristic value.

12. The method of claim 11 wherein the source digital images have pixels corresponding to different colors and step d) includes the step of generating the residual histograms as a function of the color and the numerical values of the received source digital image pixels and calculating the corresponding noise characteristic values as a function of the color and the numerical values of the source digital image pixels.

13. The method of claim 1 wherein the source digital images are received from a single image capture device including a digital camera, a photographic film scanner or a print scanner.

14. The method of claim 13 wherein all of the source digital images are derived from the same photographic film type.

15. The method of claim 1 wherein all of the source digital images are derived from the same consumer.

16. The method of claim 1 further including the step of using the noise characteristic value to enhance the appearance one or more of the source digital images.

17. The method of claim 1 further including the step of using the noise characteristic value to control the behavior of a spatial filter to enhance the appearance one or more of the source digital images.

18. A computer storage medium having instructions stored therein for causing a computer to perform the method of claim 1 .