Understanding the relationship of aperture and shutter speed.

[Miracle]

Alrighty... pretty basic stuff here... but I figured someone would learn something here. If you understand both shutter speeds and apertures, in and of themselves... I'll now show you how they relate to one another. On most cameras, even the cheaper point and shoot cameras, you should have what is called a Manual Exposure setting. It could be represented by the letter M or something similar... check your owners manual. In that manual mode, the camera will give you the opprotunity to set the aperture and also the shutter speeds, to acheive the desired effect in an image. Now when you study the relation of a shutter speed, as it relates to the aperture, you have to understand the importance of, "Change one, adjust the other." Say you want to compose an image with a shallow depth of field, where everything beyond the subject of the picture, is out of focus (blurry). This is what I am talking about: See how I, as a photographer, basically "tell" you what I want you to look at? Which in this case would be the pony in the grille. I want you to focus your attention to that, and only that, and I do that by setting a wider (lower F/stop number) to achieve that desired effect. Choosing a narrower (higher f/stop number) aperture would render more of the image into clearer focus. BUT... BUT... here is where the relation of aperture to shutter speed comes into play. When I open up the aperture (to in turn blur alot of the picture), it lets in ALOT of light. Now, for the camera to get a perfect exposure, I will need to adjust the shutter speed accordingly, to "inhibit" more light than nessecary to expose the image correctly. In that above example, I used a full manual exposure setting on the camera, and set the aperture to f3.5, and the shutter speed to 1/500th of a second. Now, you will not ALWAYS need a 3.5 aperture when you use a 1/500th of a shutter speed. The amount of light available, which direction the light is coming from, and even the TYPE of light will affect the aperture/shutter speed combo. Now... here is another example. Say I want to get a perfectly "frozen" image. One that looks like everything is stopped in motion, and I want it to look like this: Notice how the car itself, the wheels, and even the lines in the road, and the buildings in the background are frozen in their motion in relation to the camera? I do that with a fast shutter... a 1/400th of a second shutter. But since I had such a fast shutter, I needed to OPEN the aperture (f4.0 in this instance) to increase the amount of light coming in to expose the image correctly. A smaller aperture value would have further inhibited light hitting the sensor on the camera, thus UNDEREXPOSING the image. Now I am not so sure about some of the cheaper point and shoots, but I know almost ALL Digital SLR cameras have what is called an Aperture Priority mode, as well as a Shutter Priority mode. Simply, all these modes accomplish when you use them, is you set what you want to set (you set the aperture in Aperture Priority mode, and the shutter speed in Shutter Priority mode), and then the camera adjusts the OTHER to make a good exposure. EXAMPLE: I want to do a stop motion shot... where say a racecar is frozen in the image, as it goes around a race track corner. I would set the camera to Shutter Priority mode, and set a shutter speed of approx. 1/200 or 1/250 of a second. The camera would automatically adjust the aperture to accomodate for the fast shutter speed. The opposite applies to Aperture Priority mode. You set the aperture, according to your desired effect, and the camera sets the shutter speed. If you need me to explain it any further... don't hesitate to ask me.

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[just Touge]

Nice writeup. Its always good to throw in something about softness and defraction too when talking about aperture.

[RedStarGsr]

i just experienced this today when shooting my brothers car...wish i had a longer exposure to get the spinning wheels effect :/

[Miracle]

Originally Posted by RedStarGsr

i just experienced this today when shooting my brothers car...wish i had a longer exposure to get the spinning wheels effect :/

Like this?

[StorminMatt]

Here's a little something else I should throw in about shutter speed and aperture. Basically, shutter speed has no effect on your picture (apart from exposure, of course). It is the APERTURE that has all the effect. Shutter speed is simply set to some appropriate value in order to ensure the proper exposure for a given aperture. This is why aperture priority is generally a MUCH more useful setting than shutter speed priority. With aperture priority, you set your aperture to get a given depth of field, and let the camera choose the shutter speed for the proper exposure.

[DevilsSi1481]

wow i love reading this stuff cause im kinda a beginner to DSLR's so this helps me out alot. i hope more people post up more stuff on this topic.

[StorminMatt]

Originally Posted by StorminMatt

Here's a little something else I should throw in about shutter speed and aperture. Basically, shutter speed has no effect on your picture (apart from exposure, of course). It is the APERTURE that has all the effect. Shutter speed is simply set to some appropriate value in order to ensure the proper exposure for a given aperture. This is why aperture priority is generally a MUCH more useful setting than shutter speed priority. With aperture priority, you set your aperture to get a given depth of field, and let the camera choose the shutter speed for the proper exposure.

I should correct myself about one thing when it comes to shutter speed not affecting the picture. It can in one important way: motion blur. If shutter speed is too long (1/60 second OR 1/lens focal length, whichever is faster in the situation) AND the camera is handheld, then the camera will move enough during the exposure to blur the picture. A tripod is needed in such situations. Also, image stabilized lenses can reduce motion blur at longer shutter speeds, but then generally cost ALOT more than comarable lenses without it.

[JakeB.]

Thanks for the contribution guys... I placed a link to this thread in the FAQ/Tutorials thread

[00ekcoupe]

Originally Posted by DevilsSi1481

wow i love reading this stuff cause im kinda a beginner to DSLR's so this helps me out alot. i hope more people post up more stuff on this topic.

[Genuine Rolla]

Nice contribution

[thaiphob]

Very clear and easy to understand. Great job man

[JDM_EJ8]

great info

[RedStarr]

Should be stickied!

[KOREAN]

Originally Posted by RedStarr

Should be stickied!

It's in the sticky with all the links.