Tripod head

Regardless of the tripod I am using, the camera points a little lower after several minutes from initial setup. This is not a problem when I shoot regular video. It becomes a problem on long exposures, HDR etc. One might say that the camera is too heavy for the tripod, but I don't want to carry heavier tripod. Another option is to wait a few minutes for stabilization, but I don't have the time.

Any idea how to eliminate the drop of the tripod head?

On my tripod(a Millar) there are locks for tilt and pan which I engage when i am filming anything for any length of time to avoid this problem . . . does your tripod head not have a tilt lock or tightener?

Yes it does have tighteners. They do not resolve the problem.

Are you using very cheap, plastic tripods because a professional tripod should be able to lock tight. The Millar and my Manfrotto does. Or is your camera just way too big and heavy for the tripod. . .. which case you may just need to get a bigger tripod.

I do use a pretty cheap tripod because it's lightweight. I think the tripod you mentioned is heavier and I cannot carry any more weight. I tested one Manfrotto in the past and it was worst because it had 4 segments in each "pod" instead of the usual 3.

You might take a look at a gitzo with carbon fiber legs. It is expensive but well worth the money for those of us who want (or need) a relatively light weight tripod.

@wideweb

I'm using a Benro C-2580F Carbon Fiber with 3 leg sections and quick release locks. It weighs 3lbs and has max height 61 inches with a maximum load of 26.4lbs. Cost is 339.00 USD. The fluid head I'm using is Manfrotto 501HDV. Total weight of the tripod with head is 6lbs and the folded height with the head is 24.9 inches.

For long time-lapse shooting use the 3-way tripod head. I have few Manfrotto 3-way heads which are very solid and never had any problems with "tripod head drop" as you described. For some time-lapse of growing plants test shootings I used these heads for few days and heavy 5DMarkII camera stayed as a rock.
Zygis

Zygis, the problem that worries me occurs in the first 10-30 seconds since I set-up the camera. My tripod stabilizes without intervention after that time. This is a problem when I take long exposure stills to different angles, and every time I have to wait for the system to stabilize.

Eden, do you have the same 'tripod head drop' effect when using small lense? Is the center weight of the camera located exactly at the center of tripod head fixing point?