How can I plot a timeline of photo counts by capture date from a folder of images?

I had a script which did something else, but it's easily modifiable to do what you want (at least the initial part):

from PIL import Image
from PIL.ExifTags import TAGS
import sys
import os
import getopt

def get_exif_data(fname):
    """Get embedded EXIF data from image file."""
    ret = {}
    try:
        img = Image.open(fname)
        if hasattr( img, '_getexif' ):
            exifinfo = img._getexif()
            if exifinfo != None:
                for tag, value in exifinfo.items():
                    decoded = TAGS.get(tag, tag)
                    ret[decoded] = value
    except IOError:
        print 'IOERROR ' + fname
    return ret

def main(argv):
    path = ''
    outputfile = ''
    try:
        opts, args = getopt.getopt(argv,"hp:o:",["path=","ofile="])
    except getopt.GetoptError:
        print argv[0] + ' -p <path> -o <outputfile>'
        print 'where:'
        print '\t<path> is the root directory path for all the images'
        print '\t<outputfile> is the CSV file to write to'
        sys.exit(2)
    for opt, arg in opts:
        if opt == '-h':
            print argv[0] + ' -p <path> -o <outputfile>'
            sys.exit()
        elif opt in ("-p", "--path"):
            path = arg
        elif opt in ("-o", "--ofile"):
            outputfile = arg

    if path == "" or outputfile == '':
        print 'error: arguments missing'
        sys.exit()
    if not os.path.isdir(path):
        print 'error: path entered is not a directory'
        sys.exit()
    photoCount = {}
    for root, dir, files in os.walk(path):
        for item in files:
            if item.lower().endswith(".jpg"):
                exif = get_exif_data(root + "\\" + item)
                if 'DateTime' in exif.keys():
                    date = exif['DateTime'][:10].replace(":","-")
                    if date in photoCount.keys():
                        photoCount[date] = photoCount[date] + 1
                    else:
                        photoCount[date] = 1

    outcsv = open( outputfile, 'w' )
    for key in photoCount.keys():
        outcsv.write(key + ',' + str(photoCount[key]) + '\n')

if __name__ == "__main__":
    main(sys.argv[1:])

When I run this on my sample directory (with a few folders of images), I get:

2011:06:21,6
2011:03:12,12
2012:03:09,168
2012:03:24,302
2011:08:27,58
2012:01:30,11
2012:02:13,848
2012:01:29,41
2012:01:21,7
2011:11:20,6
2012:01:24,25
2012:01:22,33

Ofcourse this needs to be sorted and all, but, this can be opened in excel and manipulated from there on.