Aperture question

[butcher]

Hi, I'm trying to learn how to play with aperture.

From what I understand, if I take 2 identical shots, but one of them with at f/11.6 and the other one at f/3.2, they should look very different. One of them should have the background out of focus... Do I understand the concept correctly?

To test this out, I took 2 shots from the same place with those 2 aperture values.

shot 1
aperture:f/3.2
shutter: 1/2000s
iso: 80
focal length:3.9mm

shot 2
aperture:f/11.6
shutter: 1/180
iso: 80
focal length:3.9mm

I don't see a lot of differences between the 2 shots. I was expected the 2nd and 3rd buoys to be out of focus on one of them.

Can someone explain to me what I'm doing wrong?

Eric

[zona5101]

it is also a function of the focal length of the lens and the subject to lens distance. the longer the focal legth the shallower the depth of field...and as you experienced, the shorted the focal length the greater the DOF. So despite the different fstops the dof on the f3.2 was already very large.

you can put some numbers to the concept by playing with an on-line DOF calculator:
http://www.dofmaster.com/dofjs.html

[butcher]

Originally Posted by zona5101

it is also a function of the focal length of the lens and the subject to lens distance. the longer the focal legth the shallower the depth of field...and as you experienced, the shorted the focal length the greater the DOF. So despite the different fstops the dof on the f3.2 was already very large.

you can put some numbers to the concept by playing with an on-line DOF calculator:
Online Depth of Field Calculator

So if I understand correctly, the focal length is controlled with my zoom... correct?

Thanks for the info. It is very useful.
Eric

[zona5101]

Originally Posted by butcher

So if I understand correctly, the focal length is controlled with my zoom... correct?

Thanks for the info. It is very useful.
Eric

yes, the zoom function changes the focal length.

[i speak in math]

due to the size of the sensor in a P&S camera, you aren't going to get a narrow depth of field. The sensor is simply too small to allow it. Some camera have slightly bigger sensors, or the apertures can open up even greater, and they will be able to achieve that look you are thinking of. DSLR can do it easily. FF camera even easier and MF needs to try really hard to get the whole frame sharp. Oh, and this has nothing to do with lighting.

[butcher]

Originally Posted by i speak in math

due to the size of the sensor in a P&S camera, you aren't going to get a narrow depth of field. The sensor is simply too small to allow it. Some camera have slightly bigger sensors, or the apertures can open up even greater, and they will be able to achieve that look you are thinking of. DSLR can do it easily. FF camera even easier and MF needs to try really hard to get the whole frame sharp. Oh, and this has nothing to do with lighting.

ok. I just did a test with the zoom, and it is close to the effect I was looking for. I will go back to the beach and try again with the buoys.

Thank you very much for your help.

Also, I thought the the aperture/shutter speed/iso was part of this disucssion group about lighting. Which group should I use to ask these questions?

thanks again.
Eric

[sk66]

To maximize the effect, get closer to your subject...You were probably very close to the hyperfocal distance for that setup...

[Statto]

Originally Posted by zona5101

it is also a function of the focal length of the lens and the subject to lens distance. the longer the focal legth the shallower the depth of field...and as you experienced, the shorted the focal length the greater the DOF. So despite the different fstops the dof on the f3.2 was already very large.

you can put some numbers to the concept by playing with an on-line DOF calculator:
Online Depth of Field Calculator

Hey Zona

Nice little calculation programme

T4S

[bhursey]

With a P&S you may have to be only a few feet away from that buoy with it zoomed in. But zooming on a P&S normal pumps the aperture up because it is not a flat lens.