<p>I am not new to photography, but new to digital equipment. I am confused about flash guide numbers. My last flash had a GN 110. I think that meant that I had to use F11 at 10 ft with ISO 100 film.<br> I now have a Olympus E510. The built in flash Guide number appears to 12m. Does that equal to a GN in Feet of 36 or F3.6 at 10 Feet? I hope not, because that means I can't shoot over 10 ft based on the largest aperture opening on my lens, unless I select a higher ISO.<br> I am looking at the FL36 flash. Based on what I understand, it has a GN of 85 at 10 ft. Is that correct?<br> Thanks from an old guy.</p>