Trouble Controling DoF

[Donal]

HI I'm a very newbee (only got a camera for my birthday at the start of August) and I'm having a problem using Depth of Field on my camera. I got a Canon powershot SX20 IS, based on reviews at dpreview.com.
Now I find that when I want to take a photo everything stays in focus. I've tried to take some shots using the Av setting but they still come out in focus instead. I've attached one of the photos that I just took (excuse the composition) and I thought, given the setting that I had, it would just show the foreground in focus and everything else "blured". It didn't....

So after that long ramble, my question is:
How do I get my Av to work to achieve a low/narrow dept of field and does focal length affect the results?

Settings for attached photo
f/2.8
1/500 sec
ISO-80

[CharlieJ]

Donal,
It looks to me like your SX20 focused on the background, actually "mid ground" and not the potted plant, as you preferred. It just happens to be in focus due to it proximity to the actual focal point. Try setting the focal point to ONE point and then use Av to set your aperture to f2.8 or something under f5.6. BTW, if your camera can be set to Av and a "Scene" mode, turn off the Scene mode and go to Program... or even Manual.

If that doesn't work, I'll take a look at the Canon User Guide and offer more suggestions. I hope this helps!

[Jim Poor]

You're not going to get a narrow DoF with a Powershot - at least not easily.

Yes, focal length affects DoF as does aperture and sensor size. The sensor size bit is why it's very difficult to get narrow DoF with a P&S camera.

Originally Posted by Donal

HI I'm a very newbee (only got a camera for my birthday at the start of August) and I'm having a problem using Depth of Field on my camera. I got a Canon powershot SX20 IS, based on reviews at dpreview.com.
Now I find that when I want to take a photo everything stays in focus. I've tried to take some shots using the Av setting but they still come out in focus instead. I've attached one of the photos that I just took (excuse the composition) and I thought, given the setting that I had, it would just show the foreground in focus and everything else "blured". It didn't....

So after that long ramble, my question is:
How do I get my Av to work to achieve a low/narrow dept of field and does focal length affect the results?

Settings for attached photo
f/2.8
1/500 sec
ISO-80

[Donal]

Thanks guys.
I'm not going to let myself get frustrated by this as I made the chice between DSLR and the bridge camera that I bought, but I would be thankful to anyone who can give me settings that will give me a narrow DoF. (high speed/low "F" No. ????)

Regards
Donal

[Jim Poor]

Shutter speed has nothing to do with DoF. Low f/# is how to get the most narrow DoF that a given camera can deliver. More distance between subject and background will cause the background to be farther out of the area in sharpest focus.

All that being said, you're just not going to get that nice, creamy soft background with that camera's sensor/lens combination without some manipulation in post processing, which is pretty difficult to do well.

Originally Posted by Donal

Thanks guys.
I'm not going to let myself get frustrated by this as I made the chice between DSLR and the bridge camera that I bought, but I would be thankful to anyone who can give me settings that will give me a narrow DoF. (high speed/low "F" No. ????)

Regards
Donal

[Tito87]

Yes, the larger the aperture, the narrower the depth of field. The longer the focal length, the narrower the DoF. The closer you are to your point of focus, the narrower the DoF. That being said, don't expect the same results with a DSLR, as you would get with a SLR.

[Jim Poor]

Actually, one should expect nearly exactly the same results from an SLR or DSLR. This is especially true of the full frame cameras. I think your confusing DSLR and P&S or "Bridge" cameras.

Originally Posted by Tito87

Yes, the larger the aperture, the narrower the depth of field. The longer the focal length, the narrower the DoF. The closer you are to your point of focus, the narrower the DoF. That being said, don't expect the same results with a DSLR, as you would get with a SLR.

[Sterling]

And you'll almost certainly never see blurred backgrounds using the wide angle end of your zoom range like you've shown here. Stand back 20 feet and zoom in on those pots and you should start to see the background blur.

[inkista]

Originally Posted by Donal

Thanks guys.
I'm not going to let myself get frustrated by this as I made the chice between DSLR and the bridge camera that I bought, but I would be thankful to anyone who can give me settings that will give me a narrow DoF. (high speed/low "F" No. ????)...

Reliably, on a bridge/P&S digicam, the only setting that's going to get you a narrow DoF is "Macro", and only if you're shooting something up close. You're hampered by several factors.

The small size of your sensor dictates equally small focal lengths. While the SX20 boasts an equivalence of "28-560mm", what's actually printed on the front of the lens is 5mm-100mm. That's your true focal length. The shorter the lens, the deeper your DoF, at 5mm, everything is going to be in focus, regardless of your aperture setting. A dSLR uses a sensor that's six times bigger, and lenses that are six times longer which is why they can get a thin DoF, but need special lenses to do macro. It's all tradeoffs.

Secondly, your max. aperture is only f/2.8 (and only at the wide end. At the tele end, it's even smaller: 5.7). That really doesn't help.

That said, things that can maximize your background blurring

• Using a longer focal length (zooming in) (this will probably increase your subject distance and your max. aperture, btw., so is probably the least useful thing to try).
• Getting closer to your subject (macro) (most effective; but may depend on being at the wide end of your zoom range).
• Separating your subject from your background as much as possible (i.e., you can't expect to blur out a background that's only two or three inches behind your subject).
• Using your widest aperture (f/2.8) (again, may depend on being at the wide end of your zoom).

[Tito87]

Originally Posted by Jim Poor

Actually, one should expect nearly exactly the same results from an SLR or DSLR. This is especially true of the full frame cameras. I think your confusing DSLR and P&S or "Bridge" cameras.

I'm sorry, but there really is a difference. If you use the same f/stop and focus from the same distance and with the same focal length ( as close as you can get, given the difference between DSLR and SLR) you'll see that it's easier to blur with the SLR.