blurred backgrounds

[zephyr]

Hi. I often see photos that show a nearby object in sharp focus with everything else in the scene very blurry, which really draws a lot of attention to the main subject. I guess this is called shallow depth of field. (Great example: http://photography-on-the.net/forum/showthread.php?t=50124)
I've been trying to get this effect with my Powershot SD800 IS with limited succes... Shooting in macro, the background is still not quite blurry enough. Not shooting in macro, say someone's face at about a yard away, does not produce any blur in the background. Any ideas how I can create a better effect with this camera?

[lantern]

You're going to have to work with how much light you let in(aperture) and how fast your shutter speed is when shooting. It's often referred to as "bokeh" I believe.

Others on the board will be able to better tell you and give you some advice on their experience. I'm just a newb.:)

Here's a link that shows what you need to do. You can read the whole thing or just skip down to the part you need.

http://www.digisniper.com/photography/tutorials/

[tedr]

Hi. I often see photos that show a nearby object in sharp focus with everything else in the scene very blurry, which really draws a lot of attention to the main subject. I guess this is called shallow depth of field. (Great example: http://photography-on-the.net/forum/showthread.php?t=50124)
I've been trying to get this effect with my Powershot SD800 IS with limited succes... Shooting in macro, the background is still not quite blurry enough. Not shooting in macro, say someone's face at about a yard away, does not produce any blur in the background. Any ideas how I can create a better effect with this camera?

Yes it is called shallow depth of field. It is a quality that varies with the aperture setting of the lens, the focal length of the lens and the focusing distance. It is very effective and control over it is one of the goals of camera craft.

I think it may be difficult to control with your SD camera because it won't give you control of the aperture and shutter settings, which is what manual controls give you. You may have to work with indirect control. I'll say more about that in a minute.

It is the reason behind the semi-auto shooting mode called Aperture priority, you set the aperture and the camera meter decides the shutter speed. This is also called shooting "wide open" because the effect is maximum when the lens aperture is set to maximum (smaller f number).

These are the rules for depth of field:

shallower DOF is given by lens wide open, smaller f numbers, that is f2 rather than f8.

shallow DOF is stronger when the subject is closer to the camera and the focusing distance is smaller, that is, focused at 1 foot the background blur is more than focussed at 5 feet.

shallow DOF is greater with longer focal length lenses, that is 10mm rather than 6mm (approx 60mm rather than 36mm in 35mm equivalent terms)

Putting these factors together: shallow depth of field will be maximum with the lens at the longest zoom setting and with the subject located as close to the camera as the lens will focus and with a wide open aperture.

I think the last one is not directly available on the SD. You may be able to force the camera towards this setting by shooting in low light, use a tripod if necessary.
In bright light the camera will automatically select smaller apertures the opposite of what you want.

You can get more of this effect with a 35mm film or digital camera because the lenses are longer focal length and have wider maximum apertures. With roll film medium format film it is more pronounced still and by the time you get to large format 4x5 and 8x10 cameras it is so pronounced as to be a nuisance under some conditions, you just can't get everything sharp.

Hope this helps

Good Luck

Ted

PS I learned about this stuff with film but it is exactly the same with digital because it is a property of physical optics.

[tedr]

PS using the rules above there are other situations where extreme shallow DOF occur and can be used creatively. Very close up even with short focal length lenses the DOF can be very shallow. I was just looking at a close up I made using my A700 of two flies, they were about 1/2inch from the camera lens, the DOF doesn't even extend the size of a fly so the background is completely blurred.
T

[zephyr]

Sounds like achieving this effect with my SD800 would pretty much always require a tripod for zoom and low light. Thanks for the tips!