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10-23-2010, 11:46 PM   #1
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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

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.

10-24-2010, 10:46 AM   #2
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Very good explination. I always advise beginners who want to really lean photography to set everything on manual for a few months to learn how the three basic elements relate to each other and how a camera handles light. It really makes photogaphy more fun and satisfying because you take control of the creative process and begin seeing all kinds of possibilities.
Auto exposures on modern cameras are very sophisiticaed and accurate, so once you lean some properties of light and how the basic elements handle it, you can use AV (AE lock) and TV to achieve most of the effects you desire.
However, I believe learning an effective manual focus techinque is most important, not only to insure the focus point is exactly where you want it (not where the camera thinks it should be based upon contrast), but to control the hyperfocal distance.
I applaud what you are doing and bet you can see a marked difference in the quality and look of your photos.
10-24-2010, 11:26 AM   #3
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Great post. This would make a great sticky.

10-24-2010, 12:06 PM   #4
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A good simple tutorial. There are a number of good books that explain this interplay well also and it would behoove the newbie interested in going beyond auto modes to invest in one, such as Brian Peterson's Understanding Exposure.

Thanks for sharing this.


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