Aperture Help

[icu222much]

I'm confused about aperture. I know that the aperture is an opening in your camera that opens and closes a certain distance, allowing for a certain amount of light into your lenses. I do not understand how this would effect the depth of field.

I also tried to do an experiment to try to figure this out myself. On a table I placed my cell phone. I placed my camera on the other end of the table (about 3 feet away). The backdrop is a window overlooking the street. I took two pictures in aperture priority mode. One was at f/5, and the other at f/22. I didn't see a difference in the picture other then the fact that one was slightly brighter then the other. Am I missing something?

Thanks,
-Jon

 

[Big Mike]

Welcome to the forum.

There is a rather technical explanation that will explain the physics of this. Maybe look up Aperture, Depth of field and Circle of Confusion.

In your example, the shot at F5 should have a background that is blurrier than the one at F22.

However, one of the factors is the size of the medium (digital sensor). I'm guessing that you have a 'digi-cam' with a small sensor...which make it hard to get a shallow DOF.

Also, F5 really isn't a large aperture. On your camera, F5 may still give you a very large DOF.

A DSLR camera with a lens that has an aperture of F2.8 (or better yet, F1.8 or F1.4) you could get a much, much more shallow DOF.

 

[R0TT3NBURIT0]

For different lighting your suposed to change your ISO (more light is lower ISO) if your pictures are not the way you would like them play with ISO.

 

[Sontizzle]

Think of Aperture as the hole in your camera that lets in light. A bigger aperture means a bigger "hole" and thus, lets in more light. Conversely, a smaller aperture will let in less light. Aperture is probably the most confusing of the 3 settings because the number (f/stop) used to describe it may seem "backwards" to most people. The lower the number, the larger the aperture, and vise versa.

For example, an aperture of f/2.8 is twice as large as an aperture of f/4.0 and will let in twice as much light. I've illustrated this below to help you visualize what I've just described:

Aperture is usually controlled in 1/3 stops, so 3 clicks of the wheel is 1 full f/stop. For example, f/2.8 to f/4.0 is one full stop. f/3.3 and f/3.5 would be one third stops in between f/2.8 and f/4.0. The minimum and maximum aperture settings are dependent on the lens you're using. More expensive lenses will usually have bigger apertures. For example, a lens with a maximum aperture of f/2.8 will usually cost hundreds of dollars more than the same lens with a maximum aperture of f/4.0.

Aperture doesn't just control the light entering the camera, it also controls what is known as Depth of Field (DoF). This is the primary reason for adjusting the aperture value on the camera and is extremely important to understand. Depth of field is simply a way of describing how much of your picture is in focus. A narrow depth of field will have very little in focus (blurry background) while a wide depth of field will have almost the entire frame in focus (detailed background).

In the example below, the picture on the left has a wide depth of field where as the picture on the right has a narrow depth of field:

Depth of field is controlled by the aperture setting. A larger aperture (smaller number) will have a very narrow depth of field. A smaller aperture (larger number) will have a wide depth of field. For example, in the images above, the left picture was taken at f/10 where as the picture on the right was taken at f/2. A good way to remember this relationship is to think of the aperture f/stops (numbers) as a measurement of depth of field. The smaller the number, the smaller the depth of field, and vise versa.

So then, why would we ever want to use a large aperture (small number)? Wouldn't we always want the most detail possible? The short answer is no, because your aperture setting will vary greatly depending on your situation. If you're looking to isolate your subject or remove a distracting background, a narrow depth of field is the best way to do so. Your subject will be in focus and the background will be blurry. Depending on how far away the background is and how large your aperture is, the background can become so blurry that it almost looks milky. This magnitude of background blur is usually referred to as "bokeh" and is a desired effect for some pictures, especially portraits.

An example of the exact opposite situation where you'd want maximum detail and a wide depth of field would be shooting a landscape or something very large. In that case, the background actually is your subject, so a blurry background would not be desirable.

To recap:

A large aperture is a small f/stop number (f/1.4, f/2, f/2.8 ).
A small aperture is a large f/stop number (f/12, f/18, f/32).

A large aperture will let in more light, but will have a smaller (narrow) depth of field.
A small aperture will let in less light, but will have a larger (wide) depth of field.





hopes this helps. i didnt write this but i found it helpful for me.

 

[evo5gsr]

For different lighting your suposed to change your ISO (more light is lower ISO)

Err...

 

[akazoly]

Sontizzle thanks Please explain me this (in more details):

This magnitude of background blur is usually referred to as "bokeh" and is a desired effect for some pictures, especially portraits.

 

[Helen B]

Think of Aperture as the hole in your camera that lets in light...
i didnt write this but i found it helpful for me.

For anyone interested, here is a link to what might be the full original article by Ben Fried. It's quite well written.

Best,
Helen

 

[adolan20]

Aperture is hard to understand because we think a bigger number must mean a bigger opening. Get rid of that logic and substitute this one: F stands for focal length, the / is divided by, so now it makes sense. For example, when you divide by a bigger number you get a smaller result ( smaller opening) and when you divide by a smaller number you get a bigger result (larger opening). That's how I remember it at least, hope that helped.

 

[akazoly]

I use the Nikon 50mm f/1.8D lens. The maximum aperture is 1.8 and minimum aperture is 22.

1.8 2 2.2 2.5 2.8 3.2 3.5 4 4.5 5 5.6 6.3 7.1 8 9 10 11 12 13 14
15 16 17 18 19 20 21 22

What this mean, f/1.8 to f/2.5 is one F-stop for me ?
Thanks!

 

[Sontizzle]

Sontizzle thanks Please explain me this (in more details):

This magnitude of background blur is usually referred to as "bokeh" and is a desired effect for some pictures, especially portraits.

in english it means the bigger aperture (smaller number) will give u a more blurred background and a smaller aperture (bigger number) will give u a less blurred background ( a more clear picture).

 

[Sontizzle]

I use the Nikon 50mm f/1.8D lens. The maximum aperture is 1.8 and minimum aperture is 22.

1.8 2 2.2 2.5 2.8 3.2 3.5 4 4.5 5 5.6 6.3 7.1 8 9 10 11 12 13 14
15 16 17 18 19 20 21 22

What this mean, f/1.8 to f/2.5 is one F-stop for me ?
Thanks!

hmm i think 1.8 to 2.8 would be one full f stop (1/3)

 

[Helen B]

Yes, f/1.8 to f/2.5 is one stop.

You multiply or divide the f-number by 1.4 (or 1.414, the square root of 2) for each stop. Starting at the minimum possible f-number, f/0.5, the sequence of full stops is as follows:

0.5
0.7
1
1.4
2
2.8
4
5.6
8
11
16
22
32
45
64
90
etc.

Best,
Helen

 

[akazoly]

Thanks, Helen.

 

[bango707]

Sontizzle thanks Please explain me this (in more details):

This magnitude of background blur is usually referred to as "bokeh" and is a desired effect for some pictures, especially portraits.

In some pictures, especially in most portraits, you want the viewer to be able to concentrate on the subject, not distracting objects in the foreground/background. Bokeh is basically the detail in the 'out of focus' objects in the picture. With poor Bokeh you can see detail (sharper, harder edges) in the out of focus objects. With good Bokeh the out of focus will be very soft, blurry, and more dream like. At least thats my perception of Bokeh.

 

[lifeafter2am]

http://www.the-digital-picture.com/Reviews/Canon-EF-100mm-f-2.8-USM-Macro-Lens-Review.aspx

Scroll down about half-way and check out the different bokeh all taken at f/16. This isn't a change of aperture or such to change DOF, just an example of the difference in the way it can look.