25th of February 2009 (Wed), 21:06
hey guys, i just got my first flash, a vivitar 285HV. while waiting for the new cactus to come out i have been reading, reading, reading. just wondering if you guys had any tips before i take my first trip out? i really like how Bert Stephani seperates his backgrounds fromhis models by making them derastically darker or lighter. any tipe on how to do this kinda stuff?
26th of February 2009 (Thu), 09:59
When you fully understand how to use a flash in conjunction with the camera you open a new door of creativity. It's really not that hard if you break down what's going on into the smaller elements. To illustrate what happens let's consider the following situation.
You are going to do a portrait of a person. The shot is outdoors. It is day time, a sunny day. The person is in full solid shade. The background within the shot you have setup is in full sun and a significant distance behind the subject.
Here's the problem... you take the shot (with no flash) and you can get a good exposure for the background, or for the subject, but not both. If you expose for the subject the background is way over exposed. If you expose for the background the subject is in dark shadow and under exposed. The camera just can not resolve this dynamic range of light.
So, one solution is to use a flash. We use the flash to lighten the darker parts of the image, the subject in this case, which 'narrows' the dynamic range of the light the camera needs to resolve.
One important thing to realize, that you already know but must grasp with making an exposure, is that the flash has a limit as to what it can effectively light up and make a contribution to the exposure. We can easily light the subject up if the flash is close enough to the subject. But it's obvious that this same flash is not going to affect the lighting of a tree in the background 100 yards away. In fact it is not going to affect much of anything much past a significant distance past the subject. We could demonstrate this by taking a picture of a typical landscape where the closest object is 100 yards away, at noon on a cloudless day. Do you think it is going to make much difference if the flash is on or off? Likely not.
So from this we can conclude that the proper exposure for the background that is not going to 'see' any affect from the flash is 100% determined by the settings of the camera and not any settings from the flash. So we know how to make a proper exposure here for the background.
Now, throw the flash into the mix and the subject in the foreground in the shade. Keep your camera settings for the background exposure the same. Don't change them just because you have a dark/shaded subject in the foreground. The job of the flash is now to expose the subject properly. We can adjust the power of the flash up or down to get the subject exposed properly, or let ETTL figure it out and adjust FEC if needed.
So. Now that we know the 'standard' proper exposure for the scenario we can use our knowledge of how exposure was made for the two parts of the scene to be creative. Since we know that the camera alone was responsible for the background exposure we can now make adjustments to the camera settings to underexpose the background. Just speed the shuttuer up, drop the ISO down, or close down the aperture, etc. from where you were on the proper exposure.. or use exposure compensation to dial it down so it will be underexposed.
Depending on what you used to create the underexposure depends on how you now need to compensate (or not) with the flash to now maintain proper exposure on the subject. IF you are using ETTL it might do ok on it's own figuring out the new power needed for proper exposure.
Keep in mind that if you use the shutter as an exposure wildcard for the background then the flash can stay at the same power as before as shutter does not effect flash effectiveness. The only thing to watch for, and you will run into it with outdoor bright daylight, is the max sync speed. You will have an upper limit with shutter speed when using a flash. Once you bang into that limit you will have to resort to other means to change the exposure, like aperture, ISO, flash power setting (in manual flash mode) or even moving the flash to subject distance... or use high speed sync setting on the flash if it has it, but this also limits the power/range of the flash itself so may or may not help.
By doing this you can create those shots where the background is underexposed and the subject is properly exposed to make them pop. Or you can do the opposite and overexpose the background but keep the subject right. You can also use color balance settings and gels on the flash to control the white balance and have it be different in the two parts of the image.
Once you understand this relationship of flash/camera and how they can control exposures of different parts of your image you can really exploit it to do these creative things. Knowing that you can control two different parts of the image in the same shot is powerful.
26th of February 2009 (Thu), 20:00
thanks for that book of a responce. now its just a matter of getting out there and putting this stuff to use
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