Off camera lighting.. and ambient light

so i recently watched a couple of videos on youtube pertaining to off camera flash.

http://www.youtube.com​/watch?v=BQXpb9Wfo_w

http://www.youtube.com​/watch?v=17UeF-hxz4E

what confused me was how the photographers shot in daylight and made the final photos to seem like it was relatively dark outside. is this something down in post production? or was it more of the cross lighting that both photographers seemed to incorporate.

Part of it is the post but mostly it is underexposing for the background. Meter for the background to be the 'moodiness' that you want, maybe underexposing it by a stop. Once you have that manual exposure, set your flashes appropriately so that they overpower the background and are correctly exposing the subject.

Such images employ 3 rules in photography:
-Basic Daylight Exposure(BDE aka Sunny 16 rule) = 1/125 @ f/11 2/3 ISO100
-Flash exposure is controlled by aperture
-Ambient exposure is controlled by aperture and shutter speed

In full sun, expose a subject with a setting of 1/125 @ f/11 2/3 with no flash - correct exposure of subject, correct exposure of environment.

In full sun, expose a subject with a setting of 1/250 @ f/11 2/3 with flash output of f/11 2/3 - correct exposure of subject, -1 stop exposure of environment.

TheHoff wrote in post #6758167
Part of it is the post but mostly it is underexposing for the background. Meter for the background to be the 'moodiness' that you want, maybe underexposing it by a stop. Once you have that manual exposure, set your flashes appropriately so that they overpower the background and are correctly exposing the subject.

Exactly. Except in my experience, I find one stop is not enough difference. My personal preference is about 1 1/2 to 2 stops which produces a significant, visual (background) difference. As Hoff correctly points out, the biggest problem you are going to have is overpowering that very large light source in the sky with your puny little strobe... but it can be done. (Watch your sync speeds when cranking down that exposure!)

And see if you can use this: Strobe sync @ 1/400: Pushing the limits.

This type of capture is what i do most of the time for outdoor portraiture. And it roots out the reason we beg for faster sync speeds for flash. To get a shallow DOF, underexposed background in daylight outdoors and subject properly lit/exposed by flash is quite a tough order to fill, especially in the Arizona sun which is harsh and bright most of the time. (not today though ) To push this desired effect the best I can do is set my shutter to max synce of 1/200 on the 5D (I sometimes 'cheat' using the Pushing the limits technique PhotosGuy mentions ^ ). Then I dial the ISO down to 100 or "L" (50). Then I check what my aperture wants to be at 1 to 2 stops underexposing the brightest background. Often times it's in the f/8 range. Too small, too much focus for shallow DOF for what i want most of the time. So I tend to shoot my 70-200 lens at 200 and get in as close as I can and still compse my subjects properly. The 200 in close will give me a shallower DOF than my 24-70 at something like 50 at f/8.

Then you have to consider that ISO 50 at f/8 is really going to work your flashes. Since I shoot with my 580EX's off camera I usually get them in as close as I can and crank them up pretty high. The main cranked to 1/2 usually and the fill around 1/8 or 1/16.

It's a fine line to walk, and sometimes you have to compromise/trade-off some of your wants. Often times I shoot from a different angle just to get a more 'cooperative' background for the light. But when everything is dialed in and it's working you really nail some nice light/shots... and then the sun/light changes on you and you go back to tweaking settings to get it all lined up again. But the look you can acheive with this technique is something my clients rave about. It gets me plenty of referals and repeat customers. Clients recognize the look as 'professional' and since it is so hard to pull off it sets you above all the 'uncle bob' shooters who just aren't going to be able to compete with this.

Dermit wrote in post #6763343
To push this desired effect the best I can do is set my shutter to max synce of 1/200 on the 5D

I shoot with a 5D also and sometimes long for that extra 50th (1/250th) that other cameras have - I'm sure you know what I mean. If you're shooting mostly portraits, I'm curious why you didn't build or buy one of the off-camera cord extensions.