Blurring issues with my 40D DSLR

wheelie2 · Oct 30, 2011

Hello

I'm new to this forum and have come looking for help and answer that my husband can not help me with. We have a Canon 40D DSLR (I think that what you call it). My husband bought it about 3-4yr ago. When looking at cameras I said I wanted one where I could take a picture of an image where the background was blurred or take a picture of an background image and have the front images blurred hope this makes sence

but I can not get the camera to do it and although my husband says it does he can not work it out either. I'm starting to think it can not be done with this model. My dad has just bought a 60D I think and it is dead easy.

Can some-one help me please

Bec

jaomul · Oct 30, 2011

From your description I think you want a photo with a shallow depth of field, where for example a person is clear but the background is blurred out of focus, or vice versa. To do this you need to set your lens to its widest aperture (set camera to av mode and turn wheel until you get smallest number possible). Where you focus then should be clear but behind or in front will start to blur. This takes bit of experimenting and works better if you have a lens with longer focal length (from perspective as its not actually focal length but aperture that decides what is out of focus). Try also to have seperation between what you want in and out of focus, for example if you take a person and you are 5 feet from them when you focus, very nearby stuff behind them will not be very out of focus but if say trees or bushes are well behind them you get the nice blurred effect

Railphotog · Oct 30, 2011

What lens are you using? Its the lens that allows the background to be out of focus/blurry. A longer/telephoto lens will do this best, with the background being farther away. Focus on your subject and use a wide lens opening, the background should be out of focus.

cgipson1 · Oct 30, 2011

This might be useful for you... Online Depth of Field Calculator . It will allow you to calculate how much DOF (depth of field) your particular gear has at various apertures and distances.

As Rail and Jaomul mentioned, this is an issue of selective DOF and learning to use it can be fun.

wheelie2 · Oct 30, 2011

Thank-you

I'm using a efs17-85mm lens. Some-one said to set to AV and work the dial. I have found the dial that moves numbers from 5.6 to 32 but do not know what it means. I'm really not up with phtography talk :scratch: Might have to find where my husband has hidden the instruction booklet. Can any-one recommend a photograhy book or site for a dummy please

I have been playing around this morning and it seems to be working. I will wait until the kids are home from school and take some pics of them outside and if brave enough will post my photos for advice. If there is also a better lens I shoukld be using can I please be told which one so I can get one

Thanks Rebecca

Dao · Oct 31, 2011

To blur the background with your 40D, you can ...

- Increase the aperture size (lower the f#) Some lenses has wide max. aperture such as f/1.8, f/1.4 or f/1.2
- Decrease the subject to camera distance.
- Increase the subject to background distance.
- Increase the focal length.

So for kids shots, set the aperture to the max allowed, Have your kid stand closer to the camera and find the spot where the background is far far away. And take the shot with focal set to longest.

PJL · Oct 31, 2011

wheelie2 said:
Thank-you

I'm using a efs17-85mm lens. Some-one said to set to AV and work the dial. I have found the dial that moves numbers from 5.6 to 32 but do not know what it means.

Av mode is aperture priority mode. It means the user sets the amount of light that is going to be let into the camera through the lens; the camera then automatically sets the shutter speed, which the amount of time the camera allows light in.

Aperture is actually a fraction based on the relationship between the size of the opening and the focal length of the lens. Therefore, the lower the number of the aperture setting, the more light you're letting in. In your case, 5.6 for that lens when you're set on an 85mm focal length would be considered "wide open" -- the most amount of light the lens can let in. The setting of 32, on the other hand, would be an opening the size of a pinhole. Very small.

The reason this is important is that the wider the aperture, the less depth-of-field you have, which means a narrower part of the photo will appear in focus. Depth-of-field is also affected by how far you are from your subject -- depth-of-field would be narrower close to the lens rather than further away from it -- as well as how far the background is away from your subject.

To get the shallowest depth of field (the most amount of blur), you want to be close to your subject, use the longest focal length you can, use the widest aperture (lowest number), and have your background be a good distance from your subject.