Quick Guide to Shutter Speed/Aperture/ISO
I've been using a DSLR for about four years...
For three and a half of them, I used it as a glorified P&S.
The reason? I never bothered to learn how to use the manual settings. Knowing what I know now, I was missing out on quite a bit. Manual mode is FUN. And honestly, you can be up and shooting in about 5 minutes once you grasp the concepts behind it.
There are three dependent settings, and one independent meter that all work together to give you a proper picture. They are:
Shutter speed
Aperture
ISO
Meter
To be honest, at its most basic level, there are really only two "knobs" to turn to really change the effect of the picture. They are the shutter speed and aperture.
Very simply stated, shutter speed will allow you to take those cool pics with motion blur (flowing water pics, car lights, etc...), and aperture will allow you to play with depth of field (really blurry backgrounds or really clear backgrounds).
ISO, on the other hand, doesn't really do anything "cool" to the picture (unless you're going for that old-school grainy filter look - but that's another story). ISO just allows you to play with the other knobs with more possibilities.
Finally, there is the meter. This is that number inside the viewfinder that tells you when the settings are correct for a given amount of light.
The best way to do this is with an example.
Let's say you're inside your house and you want to photograph that tacky centerpiece on the dining room table under the dimly lit chandelier. Since you want the background to be blurry, you're going to need to adjust the aperture knob. In this case, you'll need a high aperture (lower F number - counter intuitive, I know). So adjust your dial to a low number (the kit lens is F3.5 IIRC). Now, looking through the viewfinder at the light meter, you'll see that it is probably telling you that you either need to increase or decrease shutter speed depending on the given light. You'll probably need a relatively slow shutter speed to take this picture, so adjust it until the meter reads "0". Now take the picture. In all likelihood, you'll notice that it is slightly blurry. This is because the shutter speed is too slow to take a hand-held shot. You could always use a tripod, but what if there were a better option? Well there may be one - ISO. Since the camera was probably set to ISO200 when you took the shot, you were limited to the slower shutter speed. If you change the ISO to 400, you'll notice that the light meter in the viewfinder is now reading higher. To fix this, you'll need to increase the shutter speed to prevent an overexposure. Just for kicks, increase it to 800, and you'll have to speed up the shutter some more. You can keep going up as much as your DSLR allows, but keep in mind that noise will become more prevalent with each increase (This is why there are so many threads on high ISO performance on the new K5 and Kr). At any rate, by changing the ISO to 800, now you'll be able to take the picture without any blur this time.
This is a simple formula for manual mode:
At a given ISO setting, aperture and shutter speed are inversely proportional. So any time you increase one, you'll need to decrease the other.
This is a very quick and rough explanation. There are a TON of possible deviations from this info, but for the most part, the basics are covered.
Had I taken the time to learn this 4 years ago, my camera would never have left the "M" setting.
Hope this helps.
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