Help with Aperture and Shutter Speed

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Permalink Reply by Matt Needham on September 8, 2009 at 8:50am

DOF is controlled by several aspects. The 3 you need to pay attention to are: aperture, focal length, and focusing distance. DOF gets shallower as: aperture size is increased (smaller f/#), focal length gets longer, and focusing distance gets closer. Shutter speed does not influence DOF.

Aperture controls DOF and exposure. Shutter controls time (how movement is rendered) and exposure. ISO is a third exposure control.

If you were doing your shots outdoors in the sun a low ISO or high shutter speed would be necessary, but in dim, indoor lighting the required shutter speeds will be slower/ISO higher.

Study up on how aperture, shutter, and ISO work together to control exposure. It's in your camera manual, any book about photography, and on a million websites...

http://photo.net/learn/basic-photo-tips/aperture-shutterspeed-iso/

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Permalink Reply by Jas Mandla on September 8, 2009 at 10:00am

Hey Matt,

thanks for replying and posting the link - much appreciated, I will have look and experiment on aperture, shutter, and ISO work together to control exposure.

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Permalink Reply by Staale Sannerud on September 9, 2009 at 3:51am

A small F-stop limits the amount of light that is let through to the sensor. A fast shutter speed also limits the amount of light that is let through. Of course your images are black - you are not letting in any light at all!

If you use a smaller aperture, you have to slow down the shutter to let in light over more time to compensate or you will get an underexposed picture. And vice versa, if you open up the aperture you must use a faster shutter speed to compensate or you will get an overexposed picture. Aperture and shutter speed are linked; more of the one means less of the other.

ISO is the third variable that is linked... you can use a smaller aperture AND a faster shutter speed, but in that case you have to use a higher ISO to compensate for the minimal light that is let through to the sensor.

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Permalink Reply by Jas Mandla on September 9, 2009 at 4:21am

Hi Staale - many thanks for your reply, so what would be the best setting to use if I wanted to keep something in focus (e.g, building) and the rest of the background blurred out?

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Permalink Reply by Colin Whiteley on September 10, 2009 at 1:14am

So what you are wanting is a shallow Depth of Field (DOF). You are probably best switching the camera to Aperture Priority (Av on a Canon) and then setting the f value to as low a number as your lens will allow. The camera will then automatically set the shutter speed so that you get the correct exposure. If you want to change the exposure a little use the exposure compensation adjustment (read the manual). If the shutter speed is too slow you may need to adjust the ISO setting where the higher ISO will allow the shutter speed to be faster. Beware of using an ISO much above 400 as you will start to get noise in the images.

Good Luck

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Permalink Reply by Jas Mandla on September 10, 2009 at 4:08am

Thank Colin, that was very helpful, will give it a go.

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Permalink Reply by Linda Sacauskas on September 10, 2009 at 6:20am

Jas, I bought the same camera about 9 months ago, also my first and had the same questions. What I found out is GENERALLY f11 will start blurring your background pretty good. There is a DOF button on the front of your camera that will show you what area in the shot will be out of focus. And Generally f6 will keep things straight. shutter speed depends on available light, low light means you need more time to get the photons to the sensor, slower shutter speed. Too much light getting to the sensor will over expose your picts so you need to speed up your shutter.

There are no set in stone recipe for any shot, only what's worked for others.

Make your own :)

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Permalink Reply by Jas Mandla on September 12, 2009 at 5:10am

Hey Linda,

Thanks for the tip, I tried it and it works a treat, much appreciated.

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Permalink Reply by Staale Sannerud on September 10, 2009 at 7:30am

It greatly depends. Generally, for a given aperture, a wide-angle lens gives a great depth of field while a long tele lens gives a small depth of field. Similary, for a given focal length, a close subject gives a small depth of field and a distant subject gives a large depth of field.

Keeping a building in focus and throwing the background out of focus is, in my opinion, iffy. A building is a large object, so you pretty much have to shoot it from a distance which means that depth of field is inherently large. Or you can stand close with an ultrawide-angle, which again means large inherent depth of field! If will certainly be difficult to get the subject to 'pop' out of a diffuse background.

In general though, use a 50mm lens or longer and an aperture of f/8 or thereabouts, this should give you a sharp subject and a moderately unsharp background when shot at close range. The longer the lens, the closer the subject and the further away the background is, the more unsharp the background will be. Opening up the aperture gives you a more blurred background but focusing becomes more critical and you may find that you cannot get the entire subject sharp.

http://www.pbase.com/ssanneru/image/115004746
(50mm, f/8, on a film Leica with a lens made in 1956. Modern stuff will be sharper in this situation)

For the ultimate in unsharp backgrounds do an f/5.6-f/8 head-and-torso shot with a really long lens against a distant background, like this (350mm focal length, subject was perhaps 10 meters away from the camera):

http://www.pbase.com/ssanneru/image/99606836
http://www.pbase.com/ssanneru/image/99606837

Or get something really exotic like the 85mm f/1.2L and shoot it wide open across the table:
http://www.pbase.com/ssanneru/image/87569405

Of course, his ears are far out of focus!

(These photos were taken with 5D and 1Ds mk II cameras, full-frame ones, which gives about one and one third stops' worth smaller depth of field than a crop camera like yours does.)

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Permalink Reply by Ed Harp on September 12, 2009 at 9:07am

The greatest teacher: shoot, experiment & learn. Shoot alot and learn some more. Be your own best critic.

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