I can't get a blurred background

[Destin]

I had it on portrait. I also tried on aperture priority and it didn't work.

He meant turn the camera to portrait orientation, aka vertical, to fit her in the frame as you zoom in more....

 

[Robin Usagani]

I had it on portrait. I also tried on aperture priority and it didn't work.

He meant turn the camera to portrait orientation, aka vertical, to fit her in the frame as you zoom in more....

No, I did mean the portrait setting and get realll close.

 

[Gaerek]

bazooka, use DOF calculator. As you can see, the mm affects the DOF.

Online Depth of Field Calculator

There was a lengthy thread several months ago regarding this. If subject distance doesn't change, then focal length affects the DoF. However, if you increase the subject distance in order to increase the focal length and keep approximately the same field of few, the DoF doesn't change. In your DoF calculator, put these values in:

First:
Focal length: 50mm
Subject distance: 20ft

Next:
Focal length: 100mm
Subject distance: 40 ft

This effectively gives you the same field of view for the increased focal length. Compare the DoF in both of those. You'll notice they're very close to the same. There are a couple of affects that make it appear blurrier at longer focal length, given the same field of view, but the DoF should be about the same.

Now, if you're talking about going from a full body shot, to say a head shot, keeping subject distance the same, then you are correct. But assuming you want to keep that full body shot, increasing the focal length simply won't work.

 

[bazooka]

bazooka, use DOF calculator. As you can see, the mm affects the DOF.

Online Depth of Field Calculator

I am recognizing a teachable moment! So help me to understand why zooming in on a blurred background doesn't cause the bokeh to have a larger radius around the specular highlight? According to the calculator, the background should be getting further out of focus (assuming everything else stays the same), thereby making the bokeh physically larger, and/or blur to become more blurry. In practice, I've never seen this happen. The aforementioned statement came from a book I read, but I'm not home so I can't quote it at the moment.

Or are DoF (distance front to back of the in-focus 'area') and amount of blur (area outside of the DoF) determined by different rules?

Gah, I'm stuck at work with nothing to do... I knew I should have brought my camera to do some experimentation!

 

[Robin Usagani]

I think it is just to determine how deep the field that are in focus. OUtside of that will be blurred. How much it is blurred.. im not really sure. I am still learning . I think it is mostly depend on how far the background is and what lens you are using.

 

[itf]

photoshop? :O

 

[bazooka]

Reading through Understanding Depth of Field in Photography ...

I think I understand, but not really. Like Gaerek said, if you keep the subject composed the same and change your FL (moving the camera closer or further away) will not change the DoF, as long as the subject is composed in the frame the same way. The calculator supports this.

But if I zoom into a ruler where I focus on a certain mark, the neighboring marks which were once in focus, will become more blurry because they are being magnified. I guess this does equate to a change in depth of field. I'll have to re-read that part of the book I guess... because it looks like I got it wrong.

I did learn something new from that article.... as you get past 50mm... the depth of field front/back relationship approaches 1:1. 2:3 relationship only exists at shorter FL's. So at 200mm, you will have almost just as much in focus in front of the subject as behind.

 

[Taylor510ce]

stand back further and zoom in. You probably still won't see a lot of blur using a P&S. Basically you need the subject to be as far from the background as possible yet closest to your camera as possible ( or zoom in on the subject from further back with the background still far behind. )

If thinking of upgrading to a dSLR, you won't have as much trouble getting background blur as with a P&S.

 

[djacobox372]

I don't understand one thing though. I f I get closer or zoom in, I wouldn't be able to get all of her (head to toe) in the shot. Would I?

Narrow depth of field is a product of longer focal lengths and larger (smaller number) apertures.

Your cameras sensor is too small to achieve the blurred background look.

Most point and shoot cameras have this problem with this because they have very small sensors, which means the image is cropped really tightly--making the usable focal lengths very short (they need wide-angle lenses because they're cropping so much).

Here's an online dof calculator: Online Depth of Field Calculator

A 5mm lens at f2.7 shooting at a subject 10 feet away gives a near infinite focal range (1.3 feet to infinity).

If you increase the focal length (zoom in) you'll also need to increase the distance to the subject (back up) which will negate the benefits of zooming in.

 

[djacobox372]

stand back further and zoom in. You probably still won't see a lot of blur using a P&S. Basically you need the subject to be as far from the background as possible yet closest to your camera as possible ( or zoom in on the subject from further back with the background still far behind. )

If thinking of upgrading to a dSLR, you won't have as much trouble getting background blur as with a P&S.

Backup up won't help as you are just trading one problem (short focal length) with another (long subject distance).

He can't achieve this look with his camera. But on the bright side, he never has to worry about missing focus. <-- something that many new DSLR owners struggle with