depth of field w/ canon a540?

Question

i'm trying to take depth of field pictures where the foreground is clear and the background is blurry, but for some reason my camera, a canon a540, is making it difficult. my smallest aperture size, a F 2.6, digital focuses all pictures to be clear, no matter how close or far the objects are two one another, or the camera to the objects. Has anyone had similar problems and can offer any advice? ANY help at all would be greatly appreciated. Thanks

Answer 1

It's going to be darn hard to "de-focus" too much using your A540 while keeping the main subject in sharp focus. The smaller the sensor, the greater depth of field you will have. Your camera has the smallest commonly used sensor. 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. Most of the more popular point and shoot cameras (including the A540) have the smaller sensors. It's only about 5 mm wide and 4 mm high. The lens on required to cover that angle of view is an ACTUAL 6-17 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.

The bigger the sensor, the easier it will be to achieve pleasing bokeh. This means moving to a dSLR, which all have sensors about 20 times bigger than the typical P&S digicam. 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. 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.

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/

Answer 2

You need to be shooting wide open at f2.8 to get the background out of focus. It may take some experimentation to lower the ISO to a point where your shutter speed is hand-holdable with the f-stop at 2.8. This is especially true on a bright sunny day.

Try using Aperture Priority Mode, use ISO 100 (if outdoors on a sunny day) set your aperture to f2.8 and see what shutter speed the camera sets. Try to keep your shutter speed at 1/125 at a minimum. 1/250 would be even better.

Good luck.

Answer 3

Your best bet for any good shallow DOF is to set the aperture to 2.6 and try using zoom. Step back as much as you need to so that you can do a 3x optical zoom (don't bother with digital zoom). The other thing to do is to get really close to the subject and get the background as far away as possible. I can get a decent shallow DOF on my A430 like this. Of course it's nothing compared to what I get off my D80 though.