 Sarah Cordes |
creating lighting balence hi, my name is Sarah and I'm fairly new to photography and very eager to learn! I have recently had problems with creating a balenced lighting in my photos(faces bleached from flash or backgrounds too dark). I know one way to solve this is by changing the shutter and aperture by stops. If anyone explain this to me in better detail that would be great! Thanks.
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Diane Dupuis |
Use the BP search tool in Q&A or google - lighting for portraits - natural, with flash, etc. You'll get lots of expertise!
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robert G. Fately |
Sarah, in case you didn't yet find anything - there are two fundamental things to understand; the f-stop/shutter speed relationship and the concept of dynamic range. Basically, there are 3 components that make for a proper exposure - the sensitivity of the film or ship (ISO 'speed'), the size of the aperture in the lens (lens 'speed') and the amount of time the imager is exposed to light coming through that lens (shutter speed). ISO is a base sensitivity - it is what it is. Shutter speeds and f-stops both effectively work in "doubles and halves". That is, 1/60th second is 1/2 as long as 1/30th second. And f2.8 lets twice as much light through as f4.0. So, the total amount of light that will hit the imager at 1/60th sec at f2.8 is identical to 1/30th sec at f4. Make sense? You'll notice the shutter speeds on your camera are all about half/double the next, within some mathematical roundings (1/60th, 1/125th, 1/250th, etc). F-stops are a little weirder - has to do with logarithms - but just remember that the progression is f1.4, f2, f2.8, f4, f5.6, f8, f11, f16 and on. You can see a pattern - that every other number is twice the value. Of course, these two things cause different effects in a photo. Shutter speed freezes motion (or not, as the case may be). You can imagine that a kid on a bike will be a blur at 1/2 second but caught sharply at 1/2000th second. On the other hand, f-stop relates to depth of field - that is, the "thickness" of the focused area. Set your lens to focus to 5 feet - you'll see that in actuality things that are a few inches in front of and a few inches behind the exact 5 foot distance are still in focus - that's depth of field. How far in front and behind is variable - depending on f-stop. The smaller the aperture (the higher the f-number) the greater the DOF. So that's about exposure. As for the "balancing" issue - that has to do with the dynamic range, or the ability of the imager to properly record bright and dark areas simultaneously. This is the harder thing to grok, since the human eye/brain combination is far far more capable than any film or chip to date. The difference between the darkest and brightest areas that an imager can record with detail is called the dynamic range. If the scene you're shooting (say, a dark interior room with an open window at noontime) has a range greater than what the imager can handle, you'll either lose the shadow detail or "blow out" the highlights. With that room example, either you can get the interior of the room properly exposed and leet the window turn into a big white square, or you could expose for the window and get the beautiful outdoor scenery but then los all the interior furnishings to the shadows. The only way to deal with this is to either add light inside (with flash, perhaps) or filter out some of the outdoor light (putting a big dark filter over the window - which in fact is what some pros and movie crews do). I hope that begins to help,
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- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery |
sounds like straight on flash with distant dark background. Flash tries to light the background and over exposes the front. Exposure compensation or changing the iso on the flash to a higher one, or changing the f/stop setting to a wider one on the flash is what you can do when you are leaving it up to the flashes auto setting to do it.
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