Live updates for synthetic long exposures

1. A method comprising:

storing, in memory of an image capture device, a buffer of images and an aggregate image, wherein the aggregate image represents a first summation of pixel values in images stored in the buffer;

displaying, on a viewfinder of the image capture device, a representation of the aggregate image;

capturing, by an image sensor of the image capture device, a new image;

in response to capturing the new image, the image capture device: (i) removing, from the buffer, an oldest image, (ii) storing, in the buffer, the new image, and (iii) updating the aggregate image to represent a second summation of pixel values in the images stored in the buffer; and

displaying, on the viewfinder, a representation of the aggregate image as updated.

2. The method of claim 1 , wherein updating the aggregate image comprises:

subtracting the oldest image from the aggregate image; and

adding the new image to the aggregate image.

3. The method of claim 1 , wherein capturing the new image occurs while the viewfinder displays the representation of the aggregate image.

4. The method of claim 1 , wherein the viewfinder has a refresh rate defined by a refresh time interval, wherein the representation of the aggregate image has a synthetic exposure length defined by a synthetic exposure time interval, wherein the synthetic exposure time interval is greater than the refresh time interval.

5. The method of claim 4 , wherein synthetic exposure time interval is at least 1000 milliseconds and the refresh time interval is less than 150 milliseconds.

6. The method of claim 4 , wherein the synthetic exposure time interval is an integer multiple of the refresh time interval.

7. The method of claim 6 , further comprising:

providing, by the image capture device, one or more user interface components configured to receive a selection of the synthetic exposure time interval from a plurality of possible synthetic exposure time intervals that are different integer multiples of the refresh time interval; and

setting the synthetic exposure time interval as selected.

8. The method of claim 4 , wherein the synthetic exposure time interval is a real-number multiple of the refresh time interval.

9. The method of claim 8 , further comprising:

providing, by the image capture device, one or more user interface components configured to receive a selection of the synthetic exposure time interval from a plurality of possible synthetic exposure time intervals that are different real-number multiples of the refresh time interval; and

setting the synthetic exposure time interval as selected.

10. The method of claim 8 , wherein n represents the synthetic exposure time interval, wherein f represents a total length of all whole refresh time intervals in the synthetic exposure time interval, and wherein capturing the new image comprises:

applying a gain of approximately 1+(n−f)/f to the new image.

11. The method of claim 1 , wherein the buffer stores at least 15 captured images in time order of capture.

12. The method claim 1 , wherein the representation of the aggregate image is a low-resolution image, and wherein previously-captured images stored in the buffer and the aggregate image are high-resolution images that have higher resolutions than the low-resolution image, the method further comprising:

receiving, by the image capture device, an indication that a shutter function has been triggered; and

storing, in the memory of the image capture device, the aggregate image, such that the aggregate image is available to one or more image manipulation applications.

13. The method of claim 1 , wherein the image capture device includes an image processing pipeline that applies tone mapping to captured images, and wherein the new image is stored in the buffer without image processing from the image processing pipeline.

14. The method of claim 1 , wherein the image capture device includes an image processing pipeline that applies tone mapping to captured images before storing the captured images in the buffer, the method further comprising:

after tone mapping is applied and before storing the new image in the buffer, applying reverse tone mapping to the new image, wherein the reverse tone mapping removes the tone mapping from the new image.

15. The method of claim 1 , wherein updating the aggregate image comprises applying image stabilization to the aggregate image.

16. An article of manufacture including a non-transitory computer-readable medium, having stored thereon program instructions that, upon execution by an image capture device, cause the image capture device to perform operations comprising:

storing, in memory of the image capture device, a buffer of images and an aggregate image, wherein the aggregate image represents a first summation of pixel values in images stored in the buffer;

displaying, on a viewfinder of the image capture device, a representation of the aggregate image;

capturing, by an image sensor of the image capture device, a new image;

in response to capturing the new image, (i) removing, from the buffer, an oldest image, (ii) storing, in the buffer, the new image, and (iii) updating the aggregate image to represent a second summation of pixel values in the images stored in the buffer; and

displaying, on the viewfinder, a representation of the aggregate image as updated.

17. The article of manufacture of claim 16 , wherein the viewfinder has a refresh rate defined by a refresh time interval, wherein the representation of the aggregate image has a synthetic exposure length defined by a synthetic exposure time interval, wherein the synthetic exposure time interval is greater than the refresh time interval.

18. The article of manufacture of claim 17 , wherein the synthetic exposure time interval is an integer multiple of the refresh time interval, the operations further comprising:

providing one or more user interface components configured to receive a selection of the synthetic exposure time interval from a plurality of possible synthetic exposure time intervals that are different integer multiples of the refresh time interval; and

setting the synthetic exposure time interval as selected.

19. The article of manufacture of claim 17 , wherein the synthetic exposure time interval is a real-number multiple of the refresh time interval, the operations further comprising:

providing one or more user interface components configured to receive a selection of the synthetic exposure time interval from a plurality of possible synthetic exposure time intervals that are different real-number multiples of the refresh time interval; and

setting the synthetic exposure time interval as selected.

20. An image capture device comprising:

an image sensor;

a viewfinder;

a processor;

a memory; and

program instructions, stored in the memory, that upon execution by the processor cause the image capture device to perform operations comprising:

storing, in the memory, a buffer of images and an aggregate image, wherein the aggregate image represents a first summation of pixel values in images stored in the buffer;

displaying, on the viewfinder, a representation of the aggregate image;

capturing, by the image sensor, a new image;

in response to capturing the new image, (i) removing, from the buffer, an oldest image, (ii) storing, in the buffer, the new image, and (iii) updating the aggregate image to represent a second summation of pixel values in the images stored in the buffer; and

displaying, on the viewfinder, a representation of the aggregate image as updated.