In general, storage capacity depends on which image size and quality you have selected.
For your information, here is the number of images recordable in a 128MB SD Memory Card in the respective image size and quality. Since the image size may vary depending on scenes and subjects, these are approximate values only.
Economy: 252/489/712/1958
Standard:128/252/391/1305
Fine: 65/130/200/712
Super Fine: 11/22/34/132
(Pixel Size: 2272x1704/1600x1200/1280x960/640x480)
Movie: 5 min. 56 sec.
Audio Recording: 4hr. 21 min. 3 sec.