IS it Purely a trial and error process?

[MoKs]

mixing ambient light with your flash in a low light (not that dark). without the light meter, how do you do it? like making ur subject pop but still save your ambient back round..

 

[Joves]

Yes or that is how I have done it. I like trial and error, especially now in the digital age.

 

[Bifurcator]

Without a light meter? Not even the one on your camera?

You flash guide tables can improve your intuition in that case. With the addition of you cameras light meter there's not too much experimentation needed - you can get very close to what you want the 1st time.

Remember the critical factors are flash <--> subject distance and your f-number. Well ISO too but...

 

[Garbz]

Only at first. Do it often enough it'll become intuition.

 

[Big Mike]

The camera's meter (or what ever you use for your usual ambient measurement) can help you out with the ambient part of the exposure. Then you only have to worry about the flash exposure. I usually use my flash in E-TTL mode, so that usually takes care of the flash exposure, although sometimes I need to adjust the FEC.

If you don't have or don't want to use TTL metering, some flash units have their own auto metering and failing that, you can calculate the flash exposure by using the Guide Number and the distance to the subject.

 

[JerryPH]

Until you have experience, it is all pretty much trial and error without a light meter. You can hedge your bets by using TTL and dropping it down to a -1/2 or -3/4 over ambient for a more natural look. Learning/knowing the "Zone System" will help your exposures a LOT along with understanding how to use your histograms.

My Sekonic L-358 came in yesterday and I see that it is going to make my shots a LOT faster to setup and a LOT less trial and error. I will also be a lot closer to my visions as I know how much of a ratio I want side to side and previously I would be "eyeing" things to get it close... whereas now I will know EXACTLY what it takes to accomplish very specific goals.

 

[andrew99]

This is covered in great detail at Strobist.com

I first shoot the background without flash in P mode on the camera and take note of the aperture and shutter speed chosen by the camera. I then switch to manual and put in the same values, but make the shutter speed slightly faster to darken the background a bit (if it is a bright sky, for example). Then adjust your aperture and flash to properly expose the subject.

Generally, the shutter speed controls how much ambient/background you'll get and the aperture controls how strong the flash is.

 

[MoKs]

Thanks a lot people. I really appreciate all your inputs.

 

[ksmattfish]

With my hand held light meter I'd figure out what shutter and aperture settings get me the background exposure I wanted, and then I'd meter the flash, and adjust flash power or flash distance to control that exposure. With a simple flash it may be necessary to control flash power with aperture, but most modern flashes offer variable power settings. I'm trying to retain aperture choice to control DOF.

Without a meter I would use the sunny 16 rule (or Fred Parker's Ultimate Exposure Computer http://www.fredparker.com/ultexp1.htm ) to figure ambient exposure, and flash guide number divided by distance to subject for flash exposure.

The above methods take a minute or so to figure. I used both when I shot film. Once figured it should remain the same unless the lighting changes, or the flash to subject distance changes.

Now that I shoot digital I quickly guestimate the exposure, take a test shot, check the histogram, and adjust. Repeat as necessary, although I can usually dial in the exposure I want in a matter of seconds. I like trial and error. It works for me. My math skills are deteriorating, but I'm using that brain power to interact with my subject and consider the scene, and I've found it results in better photos.

 

[Mike_E]

KS beat me to it. Follow his link.