gavin_hicks

<p>Thank you to both responders, this is very helpful as it makes me look more carefully at the Canon manual and I understand what you say.</p> <p>Exploring an old smaller flashgun I have (Guide Number 15, m/100asa) I see now that by putting the 6D on manual, choosing say 1/60 shutter speed and f11 with the 270 EX II means that I can cover up to GN 27/f11 = 2.45m with that flashgun.</p> <p>Moving up 4 stops to 1600asa with the 270 EX II gives me an effective Guide Number of 108, so GN 108/f11 gives me almost 10 metres usable range. As you say, the automatic/E-TTL function of the camera means that at any distance up to 10 meters the correct illumination is calculated and perfect exposure achieved.</p> <p>Thank you, it's just that it seemed obvious to use P mode, thinking that allowing the camera and flash to do everything automatically would, similarly automatically, give me the result I wanted, whereas a speed of 1/60 and full opening is the 'norm' in P mode. </p>

<p>I have owned a 270 EX II for a while and have used it with my 6D (I keep two of these to save changing lenses too often) and a 100D.</p> <p>On a recent shoot with a 6D and 24-70 2.8 (older mk I), on P mode (program auto) I find that although all my photos are perfectly exposed the camera/flash insists on using a large aperture and slowish shutter speed for every shot. This means, at f4, (and 1/60 sec) that in all my group shots (distance 2 to 3 meters, 1600ASA) only the faces I have used for focus are coming out really sharp.</p> <p>At this distance, with a flash of this power, and at 1600ASA, I could surely expect to see a smallish aperture and good depth of field.</p> <p>This is both mystifying and annoying. Flash photos are normally pin sharp under these circumstances.</p> <p>I've put the flash on all 3 of my camera bodies and have the same experience with all of them. The 270 EX II is of course almost entirely automatic, so I am thinking it is either an issue with this particular flash gun, or it is the algorithm/settings inherent in the gun which is making it do this. But if the latter is the case and other users had the same experience, I would expect to see this issue being discussed, but I can't find anything anywhere!</p> <p>I know I can put the camera on to Av mode, but if I insist on using a medium aperture, say f8, the camera just uses an incredibly slow speed such as 1/4 sec. Not surprisingly hand-held photos then have a blur.</p> <p>I have otherwise gone into the flash menu on my cameras and looked at the 4 modes which offer options, but nothing I do changes this exposure issue.</p>