help with shutter speeds and f-stops numbers
I am having a hard time getting f-stop and shutter speeds down. I understand how they work. However I am having a hard time with the numbers. Putting them together with one another. Is something else I can try. Matching the numbers is the hard part I think. I can use AV to help but I want to use manaul also so I would think that I would need to know that stuff....
Joe, You didn't say what camera you use; however, if you have a manual mode, then there is a way to determine when you have correct exposure.
If you are going to shoot in manual, you'll need to understand the effects of various aperture settings as well as what shutter speed settings will will allow. (I recommend you read one of the many excellent books on just how to achieve correct exposure.)
For instance, on my Nikon D200 and D70, I determine the aperture I want to achieve the desired DOF. I then look thru the viewfinder and dial in the shutter speed that will give the correct exposure. I'll check the histogram and adjust the speed up or down until I get the desired result.
You may want to learn exposure by using the Av mode and make note of the effects on exposure as you vary the aperture. Also note what shutter speed your camera selects under various lighting conditions for selected apertures.
You don't need to go on a "photo shoot" to learn; just go out in your backyard and practice.
|Alan N. Marcus||
First let's tackle f/numbers:
The job of the lens is to project an image of the outside world onto the film or digital chip. Thus the camera system acts like a slide projector backwards, the film/chip being the screen. Now how bright the image on the screen will be is a function of several factors. For this discussion we are only interested in the lenss working diameter which is defined as the lenss aperture. We need the ability to change the working diameter to make the screen image brighter or dimmer. Years ago it was determined that the best way to do this was to use an increment that either doubles or halves the screen brightness.
How big must the revised pit be to double the amount of collected rain water? Answer: You multiply the pit diameter (8 feet) by 1.4142. This value is the square root of 2. The answer is 11.3 (rounded its 11 feet). You order the pit expanded to 11 feet diameter. Surprise, this new value causes the pit to accumulate twice as much water as before. Why? The surface area (catch basin) now has double the surface area; thus it can capture twice the amount of rain.
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