Aperture - A general explanation for a newb

[NikTyler]

So yeh.. I definitely new to the world of Photography. I've spent the last month watching hours upon hours of tutorials, reading countless books, spent over $4,000 in gear and practiced everything I've learned in field with camera.

The one thing I'm not even close to clear on is Aperture and what/where settings are appropriate. I've found a bunch of sites that explain it in very technical terms - but I'm looking for more of a general explanation.

If anybody could offer this, I would be forever grateful!

[candleman]

Aperture selection depends on the situaltion, and what you are trying to achieve.... as well as several other factors.

A better way to approach it is ask what you want to achieve, and then choose the aperture accordingly.
Learning exactly what the f/stops mean is probably explained best by posting an example image and we can explain why that particular aperture was chosen.

Generally..
Wide apertures (small numbers) let in tons of light and the "depth of field" or the area that is in focus is very narrow.
Often used for portraits... or in very dark situations.

Narrow Apertures (the big numbers) let in less light and the Depth of Field is broader, meaning more of the image is in focus... good for landscapes, or bright situations to cut down the amount of light.

[4Laura]

I found this the other day - hope it helps!
cameraDemo

[OceanHorizons]

I'm in the process of wrapping my head around all this, too. I've found these articles helpful:

Moving Toward Manual Settings: Understanding Aperture (a beginner’s guide)

Learning about Exposure – The Exposure Triangle

Back to Basics - Depth Of Field | DIYPhotography.net

[NikTyler]

Originally Posted by candleman

Aperture selection depends on the situaltion, and what you are trying to achieve.... as well as several other factors.

A better way to approach it is ask what you want to achieve, and then choose the aperture accordingly.
Learning exactly what the f/stops mean is probably explained best by posting an example image and we can explain why that particular aperture was chosen.

Generally..
Wide apertures (small numbers) let in tons of light and the "depth of field" or the area that is in focus is very narrow.
Often used for portraits... or in very dark situations.

Narrow Apertures (the big numbers) let in less light and the Depth of Field is broader, meaning more of the image is in focus... good for landscapes, or bright situations to cut down the amount of light.

Ok so I took this picture of the back of my Audi the other day -



Uploaded with ImageShack.us

The F-Stop is f8 and the Exposure time is 1/200

Basically if I dropped the F-Stop to a lower number like f/3.5 it would bring everything outside of the center a little more out of focus? But I would have had to lower my shutter speed to allow more light in?

Is that sound right?

[LeeR]

I think that the most confusing thing about aperture is that numbering is counter-intuitive. When the iris in your lens is wide open and letting in loads of light the f number is tiny. I mean, f1.4 is wide, wide open. But, when there is only a tiny hole and it is only letting in a fraction of the light available, the number is large, like f22. Then, as if that isn't confusing enough, you have to layer in what is going on with depth-of-field. Here the numbers begin to make a bit more sense: small numbers mean very little DOF, large numbers, greater DOF. If you can keep those diverse concepts in the right order, you've got it made, but it isn't easy.

[NikTyler]

Originally Posted by LeeR

I think that the most confusing thing about aperture is that numbering is counter-intuitive. When the iris in your lens is wide open and letting in loads of light the f number is tiny. I mean, f1.4 is wide, wide open. But, when there is only a tiny hole and it is only letting in a fraction of the light available, the number is large, like f22. Then, as if that isn't confusing enough, you have to layer in what is going on with depth-of-field. Here the numbers begin to make a bit more sense: small numbers mean very little DOF, large numbers, greater DOF. If you can keep those diverse concepts in the right order, you've got it made, but it isn't easy.

I think.. I'm starting to understand this.. You guys are amazing...

I wonder why every studio portrait photographer I read articles on says to keep my f/stop at 11? Is that the "safe" aperture?

Also - Architectural shots I am guessing should be a higher aperture like f/16 to keep most of the room in focus?

[dakwegmo]

Originally Posted by NikTyler

The F-Stop is f8 and the Exposure time is 1/200

Basically if I dropped the F-Stop to a lower number like f/3.5 it would bring everything outside of the center a little more out of focus? But I would have had to lower my shutter speed to allow more light in?

Is that sound right?

The first part is correct. Using a larger aperture would mean that there's a shallower depth of field, a smaller portion of the image will be in focus.

Going from f/8 to f/3.5 you're actually letting in more light (the smaller the number the larger the opening). In order to compensate for the increased light, you would need to speed up the shutter speed by two and a third stops, from 1/200 to 1/1000.

[NikTyler]

Originally Posted by dakwegmo

The first part is correct. Using a larger aperture would mean that there's a shallower depth of field, a smaller portion of the image will be in focus.

Going from f/8 to f/3.5 you're actually letting in more light (the smaller the number the larger the opening). In order to compensate for the increased light, you would need to speed up the shutter speed by two and a third stops, from 1/200 to 1/1000.

I got it!

WOOOOO!!!

<3 you guys.

[inkista]

Originally Posted by NikTyler

... The one thing I'm not even close to clear on is Aperture and what/where settings are appropriate.

Aperture is the size of the iris opening in the lens (specifically, its diameter). The bigger the opening, the more light you grab at once. The smaller the opening the less light you grab at a time. So, as an exposure setting, the faster the shutter speed you need, or the lower the light levels, the wider the aperture setting you want to use.

In addition, aperture also affects your depth of field (although it's not your only control for this). So the larger the depth of field you want, the smaller the aperture you use, and vice versa.

f/4 and f/5.6 can be seen as your middle-of-the-road, plain vanilla, no special flavor aperture settings. they give you an adequate amount of light, and an adequate amount of depth of field. General purpose outside shooting.

f/1 to f/2.8 are the "fast" apertures. They're the ones you use for shallow depth of field, or grabbing a lot of light quickly, so you can use faster shutter speeds. Typically for indoor without flash (available light) or portrait use.

f/8-f/22 are the "small" apertures. You mainly use these to get a large depth of field, and often where you can shoot supported on a tripod, and don't have to worry about getting a fast enough shutter speed to handhold. Landscape shooting or macro photography are the two main areas this occurs.

However, there are two other considerations which boil down to: only go to the extremes if you're ok with the drawbacks.

Why you don't want to shoot wide open: lens performance is not identical across the aperture range. Most lenses are at their sharpest one or two stops below wide open. Similarly, chromatic aberration and vignetting (darker corners) can also be reduced by stopping a lens down from wide open.

Why you don't want to shoot stopped all the way down: aside from the shutter speed/handholding issue, there's also the fact that diffraction effect is more visible with digital than it was with film. Using extremely small apertures, like f/22 and f/32 may actually reduce sharpness, and (with crop factors) may not increase your DoF much over f/16.

One of the main things to remember is that the aperture is given as an f/# ratio (or fraction). Just as 1/8 is smaller than 1/2, f/8 is smaller than f/2. And the f-number scale is NOT a linear one. It's a square-root-of-two scale. While you don't have to do the math, the practical upshot of this is that the smaller the f-numbers go, the larger the differences become: the difference between f/1 and f/1.4 is the SAME as the difference between f/22 and f/32: one stop.

The key in terms of exposure is understanding what a stop is, and it's simple: it's just a doubling/halving of the light. With aperture, it's the f-numbers on the full-stop scale:

1 -> 1.4 -> 2 -> 2.8 -> 4 -> 5.6 -> 8 -> 11 -> 16 -> 22

With iso or shutter speed, it's actually doubling/halving of the setting number. So, exposure-wise, bopping from f/2 -> f/2.8 is like going from iso 800 to iso 400, or from 1/200s to 1/100s. This is the key to messing about with the three exposure settings of iso, aperture, and shutter speed. Given what the image calls for, you can trade them off against each other.