How to achieve a shallow depth of field with a point and shoot?

[fletch]

I stand corrected!

[seekbeauty]

As a beginner, I really don't know what field of view, dynamic range and diffraction effect are...

Originally Posted by inkista

Well... technically that's not true. Focal length doesn't actually change the DoF. But in the image it looks like it does, so it's generally taught that way. You'll notice I was weasely and wrote "to increase out of focus blur," not "to decrease DoF".

You'll note, however, that 6x is also the crop factor for a 1/2.5" sensor.

The best explanation I've seen of sensor size and its effects on noise, field of view, dynamic range, DoF, and diffraction effect is the one on Cambridge in Colour.

[fletch]

Originally Posted by seekbeauty

As a beginner, I really don't know what field of view, dynamic range and diffraction effect are...

It doesn't really matter that much so I wouldn't worry about it. If you want to get the nice blury background then just follow the simple advice above. Namely...

Get close to your subject
Zoom in
Make sure the subject is as far away from the background as possible
Use a large aperture (small f/numbers) if your camera can control this.

[inkista]

Originally Posted by seekbeauty

As a beginner, I really don't know what field of view, dynamic range and diffraction effect are...

Well, that's why I linked to the article. But here are a few quick definitions:

Field of view: how much of the scene in front of you gets to the sensor. Your focal length (zooming) affects this, but your sensor size does, too (also called "crop factor").

Dynamic range: the total range of values between black and white. A typical camera/film/monitor can capture about 5 stops (EV), while the human eye can distinguish about 10 EV (i.e., sky looks blue to you, but white to the sensor)--the human eye has a higher dynamic range than the camera. Again, sensor size can affect the dynamic range the camera can capture.

The diffraction effect, or diffraction limit means that due to the way light spreads, there's a point at which stopping down (using a smaller aperture) will make a photo blurrier. And the smaller your sensor, the wider the limit becomes (e.g., a 1/2.5" sensor can be diffraction-limited at f/4).

[Mr Guy]

Originally Posted by inkista

Well... technically that's not true. Focal length doesn't actually change the DoF. But in the image it looks like it does, so it's generally taught that way. You'll notice I was weasely and wrote "to increase out of focus blur," not "to decrease DoF".

You'll note, however, that 6x is also the crop factor for a 1/2.5" sensor.

The best explanation I've seen of sensor size and its effects on noise, field of view, dynamic range, DoF, and diffraction effect is the one on Cambridge in Colour.

The article you linked makes me stabby. The premise is almost completely worthless because the author demonstrates an entirely different physical property of light in order to make his premise.

Your statement, "Focal length doesn't actually change the DoF" is 100% false without the weasel words the author includes: "if the subject remains the same size".

That's because the depth of field is entirely the result of three variables, for any given sensor size:

A: Distance to Subject
B: Focal length of lens
C: Aperture size

The author is pretending focal length doesn't matter by changing the distance to subject. That's a perfectly fine thing to do, but only if you KNOW that's what he's doing. I repeat again: He's holding his depth of field constant when changing one variable ONLY by a change in another.

For the question that was asked, it's a VERY important bit of information because with a point and shoot you ABSOLUTELY WILL change your depth of field by zooming in and out. That's why with a point and shoot you absolutely want to use the maximum zoom that will contain your subject from the distance you're at if you want to minimize your depth of field.

All the article you link says is that if you zoom in, and then back up, or zoom out and then move forward, you'll cancel out the change, which is true and good to know.

[fletch]

To me the statements he makes seem OK ish. He is trying to say that for a given size of subject (i.e. the picture you want to take) it doesn't matter what the focal lenght is the DoF will always be the same. I.e. as DoF is a funtion of focal lenght and distance from subject they must be inversley proportional. You can increase one and decrease the other and still get the same answer out of the equation.

In your expample when you zoom in the P&S the DoF gets narrower but the subject also gets larger in frame so although you are altering the DoF you are also altering the picture you are taking which could be looked at as another variable.

Both have limitations in the real world though. You can't always zoom in if the scene you want to capture is wide. For his example; the subject size in frame is not what makes a picture, it is the subject size and the field of view and this changes at different focal lenghts. All of this doesn't really change anything. If you want to get a blured background you still do the same things...

Get close to your subject
Zoom in
Make sure the subject is as far away from the background as possible
Use a large aperture (small f/numbers) if your camera can control this.

[iluvrobots]

Thanks so much for this! I have the Canon Powershot SX10 IS as well and have been messing with my camera all night trying to get a shallow DOF for subjects that were not up close. I got everything right except I didn't think to zoom in. This will completely change the way my photos will look. I am so excited! I just need to charge my batteries so I can keep experimenting!

Here's a photo of my success:

Originally Posted by Samanax

I've seen quite a few P&S shots that had shallow DOF.

Try putting the camera in M (Manual) mode or Av (Aperture Priority) mode and then set the camera to it's smallest aperture setting (largest aperture opening). You can even try using the Portrait mode. Zoom the lens out and then get fairly close to your subject. Make sure that the subject/object isn't close to the background. Use a tripod if necessary.

Also, see this tutorial for more info.

[Mr Guy]

Awesome, glad we could all help!

[Samanax]

Originally Posted by iluvrobots

Thanks so much for this! I have the Canon Powershot SX10 IS as well and have been messing with my camera all night trying to get a shallow DOF for subjects that were not up close. I got everything right except I didn't think to zoom in. This will completely change the way my photos will look. I am so excited! I just need to charge my batteries so I can keep experimenting!

Here's a photo of my success:

Nice test shot...DOF is pretty shallow and you got a nice blur going on in the background. Nice job.

I used to think that you couldn't do shallow DOF with a P&S but after viewing a few amazing pictures on Flickr (taken by teenagers...oh to be young and carefree again) I knew I was so wrong.

[Iguanasan]

I have a Canon PowerShot SX110 IS and have played with it enough to discover the same capabilities. The limitation, however, comes in when you want a shallow depth of field on an object that is far away.

I tried to take a shot of a sailboat and put it in focus and everything behind it out of focus but it will not work unless you are practically on top of the boat. So, for portraits or macros it works great but trying to achieve DOF in landscapes is near to impossible with a P&S.

Regards, Iguanasan