System and method for capturing time-lapse photographs

1. A method for generating a sequence of time-lapse photographs, the method comprising the steps of:

a. entering into a software program installed on an electronic device a camera aperture value, a camera sensitivity value and a camera shutter speed value to establish an initial image luminance near the desired image luminance value;

b. executing the software program to control a camera to capture a plurality of images having a time-lapse interval between said images;

c. gradually increasing the camera shutter speed value to maintain said desired image luminance;

d. incrementally increasing the camera sensitivity value when the camera shutter speed value increases beyond the camera sensitivity shift time;

e. causing a corresponding reciprocal change in the camera shutter speed value whenever the camera sensitivity value changes incrementally;

f. automatically and gradually increasing the camera shutter speed value by the software program to maintain the desired image luminance when the camera sensitivity value has not attained a maximum value; and

g. incrementally increasing the camera sensitivity value whenever the camera shutter speed value increases beyond the camera sensitivity shift time and making a corresponding reciprocal change by the software program in the camera shutter speed value whenever the camera sensitivity value is incrementally changed.

2. The method of claim 1 further comprising:

a. entering an aperture minimum lens f-number value, an aperture maximum lens f-number value and an aperture value shift time into the software program;

b. incrementally decreasing the camera aperture value when the camera shutter speed value increases beyond the aperture value shift time; and

c. causing a corresponding reciprocal change in the camera shutter speed value by whenever the camera aperture value or the camera sensitivity value changes incrementally.

3. The method of claim 1 wherein the desired image luminance value is a measure of the apparent brightness of an image.

4. The method of claim 1 further comprising entering latitude and longitude coordinates into the software program.

5. The method of claim 4 wherein a minimum bulb time of the camera is greater than 0.1 seconds and less than 30 seconds.

6. The method of claim 4 wherein the calculation of the TEV is accomplished by:

a. performing a check to verify whether the camera is capturing a first image;

b. calculating a current brightness (BRIGHT now ) based on a latitude and a longitude coordinate and a time-of-day value if the camera is not capturing the first image;

c. calculating a predicted change in brightness (BRIGHT delta ) by subtracting a previous brightness (BRIGHT prev ) from the BRIGHT now ;

d. calculating a predicted absolute luminance (ALUM pred ) utilizing a previous absolute luminance (ALUM prev ) and the BRIGHT delta ;

e. calculating a TEV next to use for the next image exposure utilizing a relative luminance desired by the camera operator (RLUM desired ) and the ALUM pred ;

f determining a new value for the camera aperture value by following a predefined curve of a aperture versus time and determining new values for the camera's shutter speed value and sensitivity value by utilizing the TEV next ;

g. setting the new values in the camera;

h. capturing an image utilizing the ALUM prev and the BRIGHT prev ;

i. waiting until the time to capture a next image; and

j. repeating steps (a) through (i) a plurality of times.

7. The method of claim 6 wherein the BRIGHT now is a relative brightness of the sky on a logarithmic base 2 scale.

8. The method of claim 6 wherein the RLUM desired is a relative luminance value desired by the camera operator.

9. The method of claim 4 wherein the software program utilizes the latitude and longitude coordinates to automatically adjust a rate of change of exposure in a period of twilight.

10. The method of claim 1 wherein the electronic device is selected from a group consisting of a camera, a computer, or a mobile phone.

11. The method of claim 1 wherein the software program calculates a total exposure value (TEV) for setting new values for the camera shutter speed value, the camera sensitivity value and the camera aperture value for capturing a new image.

12. The method of claim 11 wherein the TEV denotes a combined exposure value of the aperture, the shutter speed, and the sensitivity.

13. The method of claim 1 wherein the software program automatically calculates a period of twilight brightness and adjusts the correct rate of brightness change.

14. A method for generating a sequence of time-lapse photographs, the method comprising the steps of:

a. entering a camera sensitivity minimum value, a camera sensitivity maximum value, aperture information, an aperture minimum lens f-number value, an aperture maximum lens f-number value, an aperture shift time and a camera sensitivity shift time into a software program installed on an electronic device, wherein the aperture shift time is the camera shutter speed value above which the software program decreases the aperture f-number;

b. entering a minimum shutter speed value and a maximum shutter speed value, the minimum shutter speed value being longer than a minimum bulb time of a camera and the maximum shutter speed value being short enough to allow for a practical time-lapse interval;

c. entering a desired image luminance value, the desired image luminance value being a measure of the apparent brightness of the image;

d. entering a camera aperture value, a camera sensitivity value and a camera shutter speed value to establish an initial image luminance value near the desired image luminance value;

e. executing the software program to control the camera to capture a plurality of images having a time-lapse interval between said images;

f. gradually increasing the camera shutter speed value to maintain the desired image luminance value during a sunset;

g. incrementally increasing the camera sensitivity value when the camera shutter speed value increases beyond the camera sensitivity shift time;

h. causing a corresponding reciprocal change in the camera shutter speed value whenever the camera sensitivity value changes;

i. automatically and gradually increasing the camera shutter speed value when the camera sensitivity value has not attained a maximum value;

j. incrementally increasing the camera sensitivity value whenever the camera shutter speed value increases beyond the camera sensitivity shift time and making a corresponding reciprocal change in the camera shutter speed value whenever the camera sensitivity value is incrementally changed;

k. repeating steps (i) through (j) a plurality of times;

l. automatically and gradually increasing the camera shutter speed value up to a maximum value specified by the camera operator;

m. incrementally decreasing the camera aperture value when the camera shutter speed value increases beyond the aperture shift time; and

n. causing a corresponding reciprocal change in the camera shutter speed value whenever the camera aperture value or the camera sensitivity value changes.

15. The method of claim 14 wherein the software program calculates a total exposure value (TEV) for setting new values for the camera shutter speed value, the camera sensitivity value and the camera aperture value for capturing a new image.

16. The method of claim 15 wherein the calculation of the TEV is accomplished by:

a. performing a check to verify whether the camera is capturing a first image;

b. calculating a current brightness (BRIGHT now ) based on a latitude and a longitude coordinate and a time-of-day value if the camera is not capturing the first image;

c. calculating a predicted change in brightness (BRIGHT delta ) by subtracting a previous brightness (BRIGHT prev ) from the BRIGHT now ; d. calculating a predicted absolute luminance (ALUM prev ) utilizing a previous absolute luminance (ALUM prev ) and the BRIGHT delta ; e. calculating a TEV next to use for a next image exposure utilizing a relative luminance desired by the camera operator (RLUM desired ) and the ALUM pred ;

f. determining a new value for the camera aperture value by following a predefined curve of aperture versus time during twilight and determining new values for the camera'shutter speed value and sensitivity value by utilizing the TEV next ;

g. setting the new values in the camera;

h. capturing an image utilizing the ALUM prev and the BRIGHT prev ;

i. waiting a time to capture the next image; and

j. repeating steps (a) through i. a plurality of times.

17. The method of claim 16 wherein the RLUM desired is a relative luminance value desired by the camera operator.

18. The method of claim 14 wherein the software program automatically calculates a period of twilight brightness and adjusts for a correct rate of brightness change.

19. The method of claim 14 wherein the software program utilizes a latitude and longitude coordinates to automatically adjust a rate of change of exposure in a period of twilight.

20. The method of claim 14 wherein the minimum bulb time of the camera is preferably greater than 0.1 seconds and the time-lapse interval is less than 30 seconds.

21. A method for generating a series of time-lapse photographs utilizing a software program adaptable to minimize flickering of an image sequence, the method comprising the steps of:

a. entering a time-of-day value into a software program installed on an electronic device;

b. entering a total exposure value (TEV) script, said TEV script in the form of a curve, a table or a mathematical function, wherein the TEV script denotes a combined exposure value derived from an aperture value, a shutter speed value, and a sensitivity value, and wherein the TEV script specifies how a camera total exposure value (CTEV) changes as a function of time;

c. entering a camera sensitivity minimum value, a camera sensitivity maximum value and a camera sensitivity shift time;

d. entering a minimum shutter speed value and a maximum shutter speed value, the minimum shutter speed value being longer than a minimum bulb time of a camera and the maximum shutter speed value being short enough to allow for a practical time-lapse interval;

e. entering an initial camera aperture value, an initial camera sensitivity value and an initial camera shutter speed value;

f. executing the software program to control the camera to capture a plurality of images having a time-lapse interval between said images;

g. gradually increasing the camera shutter speed value to maintain the CTEV as specified by the TEV script;

h. incrementally increasing the camera sensitivity value when the camera shutter speed value increases beyond the camera sensitivity shift time;

i. causing a corresponding reciprocal change in the camera shutter speed value whenever the camera sensitivity value changes incrementally;

j. automatically and gradually increasing the camera shutter speed value to maintain the camera CTEV as specified by the TEV script when the camera sensitivity has not attained a maximum value;

k. incrementally increasing the camera sensitivity value whenever the camera shutter speed value increases beyond the camera sensitivity shift time and making a corresponding reciprocal change to the camera shutter speed value whenever the camera sensitivity value is incrementally changed;

l. repeating steps (l) through (m) a plurality of times; and

m. automatically and gradually increasing the shutter speed to maintain the CTEV value as specified by the TEV script up to a maximum value specified by the camera operator.

22. The method of claim 21 wherein the minimum bulb time of the camera is preferably greater than 0.1 seconds and the practical time-lapse interval is preferably less than 30 seconds.

23. The method of claim 21 further comprising:

a. entering aperture information into the software program;

b. entering an aperture minimum lens f-number value, an aperture maximum lens f-number value and an aperture shift time into the electronic device, the aperture shift time being a shutter speed value above which the software program decreases the aperture f-number;

c. incrementally decreasing the aperture value when the shutter speed increases beyond the aperture shift time; and

d. causing a corresponding reciprocal change in the shutter speed value whenever the aperture value or the camera sensitivity changes incrementally.