All the answers to date have been correct, despite apparent disparity. Yes, you can log the time if you are rated in the airplane and sole manipulator, however no, you shouldn't.
Under FAR 121.385, the certificate holder designates the pilot in command. The authority and designation of PIC does not change during the flight with transfer of the controls. While one need not be designated pilot in command to log PIC under FAR 61.51(e)(1)(i), virtually any employer will look upon the logging of this time as PIC as improper.
Once you are flying for a certificate holder, you are obligated by common consent in the industry to log PIC time only when designated as PIC, and SIC when designated as SIC.
This becomes significant when applying for a job at a later date. You will be asked to exclude all time from your PIC totals for which you were not designated the pilot in command or had "signed" for the airplane. In such cases, the totals you list will be different than your logbook totals, if you have been logging sole manipulator SIC as pilot in command.
There is a lot more leeway under FAR 91, but unless you're the captain (or co-captain on flights under 91 in which PIC authority and responsibility may be trasnferred back and forth), don't log the time as PIC.
Remember that you're not obligated to log any time except that required to meet recency of experience requirements, and to meet the requirements of certificates and ratings. Outside that, you are not obligated to log your time. As you have the choice, it's best to make the choice to log it in the most favorable way toward you, and this will include logging SIC strictly as SIC, until given PIC authority in the aircraft. Under 121, the certificate holder must designate the PIC.
FAR 135.109(b) is more explicit, stating specifically that the pilot-in-command designated by the certificate holder shall remain pilot-in-command at all times during the flight. FAR 121.385 doesn't make that precise a distinction, but it isn't necessary, and the implication is clear. There is only one PIC, and that individual is previously (and irrevocably) designated before the flight by the certificate holder.