Effects of Aperture, Shutter Speed and ISO On Images

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Phil Marsh
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Effects of Aperture, Shutter Speed and ISO On Images

Post by Phil Marsh » Thu Apr 09, 2015 10:12 am

A Picture To Show You Clearly The Effects of Aperture, Shutter Speed and ISO On Images

Paul Burrows of Leica Geosystems tweeted a link to this useful post this week so I thought I'd repost here. All great info if you still learning about photography.

http://www.lifehack.org/articles/lifest ... html?dgs=1

Image
Want to capture excellent photos? Then you need to understand three things — the aperture, the shutter speed, and the ISO.

The aperture controls light that passes through your camera lens. If you shoot with the aperture adjusted to the smallest opening, the smallest amount of light is allowed to enter. Let’s say, you need to take a picture in an environment that’s too bright — how do you fix that? Simple — just choose a smaller aperture. The aperture’s sizes are measured by f-stops. A higher f-stop means a smaller aperture hole while a lower f-stop means a bigger aperture opening.

Now, the shutter speed. It’s the duration of time a camera shutter is open to allow light into the camera sensor. Shutter speeds are usually measured in fractions of a second. Fast shutter speeds allow less light into the camera sensor and are used for high-light and daytime photography while slow shutter speeds allow more light into the camera sensor. Obviously, slow shutter speeds are ideal for nighttime photography.

Finally, the ISO. ISO is all about the sensitivity level of your camera to available light. Usually, it’s measured by numbers. A lower number represents lower sensitivity to light while higher numbers mean heightened sensitivity. The drawback in using increased sensitivity is that it produces noisier images. Simply put, you end up with grainy pictures if you use high ISO.

How do you take properly exposed photos, then? Those that are not too dark or too bright. The three – Shutter Speed, Aperture, and ISO – need to play together well. Let’s say it’s high noon. Of course, you have plenty of sunlight. If your camera aperture is very small you block most of the light. It means the camera sensor needs a longer time to gather light. Now, for the sensor to collect enough light, the shutter has to stay open longer. In other words, you need a slower shutter speed.

Look at the diagram featured here. From the top, the first level represents aperture sizes, the second level represents shutter speeds, and the third level represents levels of ISO.

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Re: Effects of Aperture, Shutter Speed and ISO On Images

Post by stefanskrobanski » Thu Apr 09, 2015 10:49 am

A very concise guide, thanks Phil.

I also find that a good understanding of white balance is useful.

Ken Rockwell's WB Guide
Examples

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Re: Effects of Aperture, Shutter Speed and ISO On Images

Post by SAttaya » Thu Apr 09, 2015 9:36 pm

One other thing about aperture - affects depth of field (DOF), i.e, the range of distances that things are in focus.

The smaller the aperture, the greater the DOF.

This is what makes a pin-hole camera work focus-wise.

So if you let in a lot of light with a big aperture (like f1.4) you will have a small DOF. You use this for portraits when you want a "soft" background.

When you set the focus length to infinity (an 8 on it's side) you are really setting a small aperture, like f22.0).
You use this for "landscape" shots of mountains.

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Re: Effects of Aperture, Shutter Speed and ISO On Images

Post by jcoco3 » Thu Apr 09, 2015 10:37 pm

Yep, Bokeh! :D The diagram shows that effect, although it is still not that easy to understand.

What took me forever to learn was that if there is nothing in the foreground then there is no effect even if your aperture is wide open. So if you took the little man out of the shot and set your aperture to 1,4 then mountain would be in focus. Please somebody correct me on that if I am wrong :ugeek:

Since we are throwing out recommendations for photography here is my favorite resource: http://www.cambridgeincolour.com/

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Re: Effects of Aperture, Shutter Speed and ISO On Images

Post by Sharas » Fri Apr 10, 2015 2:57 am

Jonathan,

that is a great website! Thanks for sharing

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Re: Effects of Aperture, Shutter Speed and ISO On Images

Post by SAttaya » Fri Apr 10, 2015 2:15 pm

jcoco3 wrote:What took me forever to learn was that if there is nothing in the foreground then there is no effect even if your aperture is wide open. So if you took the little man out of the shot and set your aperture to 1,4 then mountain would be in focus. Please somebody correct me on that if I am wrong :ugeek:
Not exactly.
Even if there is nothing in the foreground and you manually set the focus to a short distance, the mountain in the background will be out of focus. (if the camera is autofocus, it will focus on the mountain. If you have a really fast focusing camera and a bumble bee gets focused on 18" in front of the autofocus, you get an in focus bee and an out of focus mountain.)

If you look at one of the non-autofocus cameras you will see f-stop bracket numbers on either side of the smallest f-stop number (largest opening). That bracket will show you the range that is in focus with that lens, set at that f-stop, focused at that distance. see https://www.google.com/search?site=&tbm ... B400%3B451, found on google images with "camera lens markings explained")

Now back to our regularly scheduled programming...

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Re: Effects of Aperture, Shutter Speed and ISO On Images

Post by dtmcnamara » Fri Apr 10, 2015 3:16 pm

The ISO grain estimations are off depending on the camera you use. I have a Canon 5D MK3 and I can shoot at 6400 with little to no grain, with my Sony a7s I can crank video to 128000 and have little to no grain visible as well.

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