Manual Photography

[Rockafeller]

Do you any of you fully understand the concept of f/stop and shutter speed and the effect they have on picture quality? More specifically, I cannot understand how f/stop decides the depth of field in a photo.

 

[Darkhunter139]

Get Understanding exposure by bryan peterson you will understand after reading that its a great book

 

[JSD]

Basically shutter speed and aperture work together to create a given exposeure. Think of it like filling up a glass with water. You can open the faucet all the way (large aperture) for a brief period of time (fast shutter speed), or you can open the faucet to get a drip drip drip (small aperture) and a longer period of time (slow shutter speed). Either way you will end up with a full glass of water, or a given exposure. This flexability is what allows you to control depth of field and motion, (either yours or the subjects), with a variety of combinations in x amount of light. If you change one setting you can change the other by an equal and opposite amount (half one and double the other for example) and have the exact same exposure, only depth of field and motion control will change. The reading the meter gives you is a starting point from which you can deviate with many combinations of aperture and shutter speed to reach the desired affect. Helpful?...JSD

 

[SushiWarrior]

Small F-stop number eg. F/1.8 = very shallow depth of field, but lots of light. The lens leaves a large opening which lets lots of light through and only gets a small portion in focus.

Large F-stop number eg. F/22 = super big depth of field, but very little light. The opening is very tiny and therefore little light gets in and almost everything will be in focus. It's similar to your eye, squint and stuff will be more in focus but darker. Also note that for sharp images this f-stop is bad because of diffraction.... basically the picture gets soft due to the tiny opening, just like when you squint.

 

[Natalie]

I understand it pretty well, but I still don't use the manual mode on my camera, simply because my photo subjects usually don't hold still so I can't sit there and fiddle with the settings for too long.

F-numbers are how wide the aperture is - how large the hole is that lets in light. An extremely wide aperture (f/2.8 for example) lets in a lot of light so you can use a faster shutter speed and lower ISO, but it also tends to cause a shallow depth of field (which can be good or bad, depending on what effect you're after). A small aperture (like f/8) creates a deeper depth of field, meaning the background will be less blurry, but also by definition lets in less light. This means you will have to use a slower shutter speed and/or higher ISO.

Here are some example photos... These were taken within seconds of each other, and are of the same animal with the same lens at the same distance. Here you can clearly see the difference a large or small aperture can make:

Aperture: f/2.8 (large)
Shutter speed: 1/250 second
ISO: 800

Aperture: f/8 (small)
Shutter speed: 1/30 second
ISO: 800

As you can see, the second photo has a much larger depth of field because of the smaller aperture. This has drawbacks, though... Just look how much I had to slow down the shutter speed! A larger aperture meant I could use a faster shutter speed, but the DOF was so shallow the photo didn't have much substance (IMO).

For things like landscape photography where you want the entire scene in focus, you often have to use a very small aperture, which in turn requires a slow shutter speed... This is where tripods will come in handy. For photographing mobile subjects, though, a tripod often isn't practical, so that generally means learning to hold your camera steadier, dealing with a shallow DOF, or getting a "faster" lens.

Hope this helps a bit and didn't make it even more confusing, hahaha...

 

[KmH]

It's explained in detail here: Digital SLR Basics