How to do Depth of Field with a digital camera?

Question

I'm a beginner at photography. I really love those pictures where an object is clear, but the background is out of focus. How do I do this on a digital camera? I have a Canon A640. I know you have to set something on the Aperture Priority to a low number, but when I do that it doesn't work. Does anyone have any suggestions? Thanks!

Answer 1

The major factors in creating shallow depth of field are the aperture (f-stop), focal length, image size, subject distance, and foreground/background differential. That's why sports photos look so great: The photographers are using 300mm lenses (at least) at f/2.8 and there are hundreds of feet of empty space behind the athlete.

You're never going to get that look with an A640 or any small digital camera. The reason is the lens isn't that long (I think it's 3x optical, which is the equivalent of about 150mm in a pro camera), and the CCD is very small, 7x5mm or so. But, to get the most out of what you have, put it in aperture priority, open the lens up to 2.8 and zoom in as far as you can (this will probably actually make the aperture less than 2.8 but that's ok). Then try to separate your subject from the background as much as possible, and also get as close to the subject as possible -- fill the frame with the subject. If there is a telephoto accesory for your camera, get that too as it will help a great deal.

Answer 2

Depth of field - the distance within a photo that is in sharp focus - is affected by the focal length of the lens, the point on which it is focused and the aperture used. Compact digitals in 'auto' mode give little control over depth of field but there are still things you can do. The main reason you would want the background to be out of focus is when taking a picture of a strong foreground subject, such as when taking a portrait. Many digital cameras have a 'portrait' mode which will choose settings that help to blur the background. If your camera allows you to change the priority when calculating an exposure, choose 'aperture priority' (often a capital 'A' on the selector dial), then choose a wide aperture (which means a LOW 'f' number). The wider the aperture, the shallower the depth of field. If you have a zoom lens, move away from your subject and then zoom-in to bring the subject up to the required size. By increasing the focal length of your lens in this way, you decrease the depth of field, helping to blur the background. Another possibility is to change the ISO setting on your camera to something like ISO 100 or even less if available. The lower the ISO number, the less sensitive to light your sensor becomes so the camera HAS to choose a wide aperture (a low 'f' number) to get the right exposure. Wide aperture = shallow depth of field = blurred blurred background. In order to get the right effect, your camera must be focused on the intended subject so you need to be aware of how your camera selects its focus and, if necessary, change your settings to avoid the camera focusing on the background. A strong foreground subject occupying the centre of the frame should do the trick though may not always be the most inspiring composition. Few compact digital cameras enable you to manually control the focus so other techniques - such as focusing IN-FRONT of your subject and relying on depth of field to keep it in focus while throwing the background out of focus - are probably not available to you. Good luck.

Answer 3

This is the best photography course online:

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You can be like the masses of humanity and buy a camera you can afford that has auto this and that for worry free picture taking. And learn through trial and error how to use something like aperture or shutter priority auto modes or even attempt to use the thing on full manual mode.
You seem to know already there is some thinking to using a camera and to take pictures. A good place to start is by reading the owners manual that comes with a camera. Read the information and look at the illustrations with part names and look at the real camera. Handle the camera and take pictures. Let me rephrase that. Take pictures to learn how to use the camera and maybe even to keep some. Don't start with important stuff you cannot photograph over again such as birthdays, a toddlers first steps. That puts picture taking out of the learning phase and puts the pressure and emphasis to taking pictures for real and to keep.
These first pictures are for you to learn how to use your camera. And you have learned how to use your camera when you can take pictures with it and can teach others how to use it. Honest. You can also go to a college in your area and take a beginning photography course. There you will be taught the basics even a pro must learn and do in their work. Camera handling and use, taking exposures with film and/or digital cameras, and maybe even some photo assignments to get some real time learning. In this learning do not take serious pictures you must keep as that detracts from the learning aspect of the class. Do so only if you have mastered the use of your camera before class is over.
It's like growing up in a way. And I am happy you know there is a way to learn how to use a camera and take pictures. It's like learning how to drive I suppose. Someone can teach you or you can get taught at a driving school. Both will get you a drivers liscense. One though will really teach you the fundamentals you can use for the rest of your driving career.

Answer 4

" I know you have to set something on the Aperture Priority to a low number"


You are confusing two terms.

First, you must select aperture priority. That is a mode setting on the camera. Not all cameras, especially point-and-shoot cameras, have aperture priority.

Second, set the aperture (f/stop) to a small number, which is the same as a large lens opening. Some lenses come with marks that show what range will be in focus for a give aperture, but often it's best to shoot with a few different settings and take the one you like the best (especially true for digital since you don't have to worry about film cost).

Answer 5

In simple terms, the depth of field is controlled by the aperture. The aperture is measured in values called f-stops, with the smaller f-stops=wider aperture, and larger f-stops=narrower apertures.

The effect you are talking about is called shallow depth of field. While images such as a landscape of a mountain and surrounding country would need deep depth of field. The blurred background is refereed to as "Bokeh."

For shallow DOF, you need an aperture of f4 and wider. However, to get truly amazing shallow DOF and Bokeh, you need an maximum aperture of f1.8, f1.4, f1.2, or f1.0. Also, a great way to get even better bokeh is to use a wide aperture, telephoto lens. For deep DOF, an aperture of f5.6 to f16 is needed, anything over f16, such as f22 will cause defraction.

This is where it gets more complicated. Along with shallow and deep DOF, this also goes along with the sharpness of an image. Shallow DOF will produce very soft, fluffy images, while deep DOF will produce excellent clarity and sharpness.

With your camera, the Canon A640, this has a manual mode. I too owned this same exact camera. It is nice and quality, but I had too many issues with image noise, and slowness.

With manual mode, switch to the widest aperture, and get as close as you can to the subject. When you do this, you'll also have to adjust the shutter speed to compinsate for all the light let in by the wide aperture.

Hope this helped.

Answer 6

I hope I have not shown these photos too many times already.

http://i30.photobucket.com/albums/c317/wtin/2fdf10ea.jpg

Antoni answered your question very thoroughly, but I'd like to show you some samples.

Same subject (nephew), virtually same distant (a few feet away behind him), same camera and same lens (Canon 50 mm f 1.8).

First one at f 1.8 (as wide as it will open), and the second one aperture was 'closed down' to f 5.6.

I should have tired to set it to even smaller (f 16 or f 22)--but I just didn't do it.

So what you need to do is to set your camera in manual (or leave it on automatic but set the aperture to higher number, thus making the entrance (to the lens) smaller.

It might not be that easy to do with your camera though.

Answer 7

Go here http://www.dpreview.com/reviews/canona640/ where you can either read the whole review or just go to http://www.dpreview.com/reviews/canona640/page17.asp to see samples with your camera. (Thanks for telling us the model of your camera. This makes it easier to give you a meaningful answer.)

You have to click through the gallery from picture number 1 to the end. Image 8 shows a bit of background Bokeh at 52mm equiv @f/3.2. Image 14 is just a little bit "defocused" in the background. Most of the images are quite sharp from near to far distances and there is a reason for that which I will explain.

It's going to be darn hard to "de-focus" too much using a digital camera while keeping the main subject in sharp focus. The smaller the sensor, the greater depth of field you will have. Generally speaking, the smaller the camera, the smaller the sensor. (Your A640 at least does not have the smallest sensor out there.) Most of the pictures you take with a digital camera are quite sharp from near to far distances and there is a reason for that which I will explain.

While we speak in terms of the 35 mm equivalency of digital lenses, don't forget that the digital sensors are usually smaller than a full-format 35 mm frame. Your A640 sensor is only about 7 mm wide and 5 mm high. The 3X lens required to cover that angle of view is an ACTUAL 7-21 mm zoom lens. At these focal lengths, the background is going to almost always be in pretty sharp focus.

In other words, if you WANT to defocus the background, you are going to have to work pretty hard at it. You would have to zoom to the longer end of the lens and set the aperture open as wide as it will go, if your camera even allows you to control the aperture, and get pretty close to your main subject while having the background a fair distance away.

Put your subjects quite a distance in front of any background that will be visible in your photo. You could use a garden of flowers and stand your subjects 20 yards or so in front of them. Try the portrait mode to shift things towards a larger aperture, zoom the lens out all the way, and move YOURSELF backwards or forwards in order to frame the picture as you would like it. In summary, you want to use a longer telephoto length, position yourself as close as you can to the main subject to compose properly, and place the main subject as far from the background that you wish to have out of focus as you possibly can.

The bigger the sensor, the easier it will be to achieve pleasing bokeh. This means moving to a dSLR, which all have sensors about 10 times bigger than your A640. If you want to really go for brokeh (very bad pun intended), you can get a Canon 5D and you will get exactly the same effect you are accustomed to in a 35 mm camera, since the sensor is the same size as 35 mm film.

Here is an example with a point and shoot camera, although it does have the larger sensor (1/1.8" - same as yours) that makes it easier to blur the background. Even though this is macro mode and f/2.8, where the background should blur the most, it's not terribly blurry because it's relatively close to the subject.

http://www.flickr.com/photos/samfeinstein/872732755/

Here is an example with a point and shoot camera, so it CAN be done. The background is much farther away, though, and this is the larger sensor size.

http://www.flickr.com/photos/samfeinstein/843563558/

Compare that to this image, though, which has a similar subject-to-background distance. The SLR has the obvious advantage.

http://www.flickr.com/photos/samfeinstein/408446616/

Wikipedia does pretty well on the subject of depth of field. See: http://en.wikipedia.org/wiki/Depth_of_field

See also: http://www.photo.net/learn/optics/dofdigital/

See also: http://www.flickr.com/groups/dof/

Answer 8

Using Aperture at f/8 to f/16,these were the best Depth of Field which could give sharper images.If you used Aperture f/1.8 or f/2.8,I don't think you will be able to get sharper image, and also without steady hands will blur the images because of less Depth of Field.Very easy do you thing so.

Answer 9

On most consumer digital cameras you can have the option to change the type of picture you are taking (auto, close-up, landscape, night, portrait, etc). Set it to close-up, it's usually a small icon of a flower, and the camera will focus on close objects with an aperture of maybe f/5.6 or f/8 (less depth of field, so your subject is clear and foreground / background is out of focus).

Answer 10

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