Aperture HELP

[pamelabw]

I am a beginner who needs some help. I've been learning the basics the past few days (iso, shutter speed, aperture, etc). For the LIFE of me, I cannot seem to make any difference in DOF in my photos when I adjust my fstop. I've been trying this is manual and AV mode.
I have a Canon G10.
WHAT is going on?

[Rentham]

Aperture is just one part of DOF. You also have to consider distance to subject, focal length, and sensor size. Shorter distance to subject, longer focal length, and larger sensor will all contribute to small depth of field.

[pamelabw]

any advice on how to get better with this?

[ang1995]

This might help you Depth of field using aperture on a camera.

It kinda helped me with a couple of questions that I had.

[inkista]

Originally Posted by pamelabw

I am a beginner who needs some help. I've been learning the basics the past few days (iso, shutter speed, aperture, etc). For the LIFE of me, I cannot seem to make any difference in DOF in my photos when I adjust my fstop. I've been trying this is manual and AV mode.
I have a Canon G10.
WHAT is going on?

You have a tiny sensor with a tiny lens. That's what's going on.

Most of the articles you read are based on the assumption you're using a 135-format-ish light-sensitive medium (film, sensor). 35mm film, a full-frame sensor, or an APS-C sized sensor when they give you f-numbers and show you DoF examples.

But a P&S camera, like the G10, has a much much smaller sensor. Cue the Wikipedia graphic:



The navy blue line labelled "1/1.7"--that's the relative size of the sensor in your G10. The 35mm "full frame" is probably what's being used in what you're reading.

DoF is affected by three things, one of which is directly related to your sensor size.

Aperture setting is only one of the three factors, and may actually be the least effective in some ways, but it's the most easily controlled, so that's why it's always mentioned. But your P&S camera already limits you in that the largest aperture setting you can use is f/2.8 at the wide angle end of the zoom range, and f/4.5 at the telephoto end of the zoom range.

The second big factor is the relative subject-to-camera distance. The larger this gets, the bigger your DoF becomes. The closer you get, the thinner the DoF becomes. With P&S cameras, a macro shot may be the only reliable way to blur the background with a thin DoF.

The third big factor is the focal length of the lens you're using. The longer the lens is, the thinner the DoF becomes. The shorter the lens is, the thicker it becomes.

When you have a small sensored camera, the lens is proportionately as small. While the G10 is speced out as having an 28mm-104mm lens--that's only its full-frame equivalency for the field of view (i.e., the framing you get is the same as if you had a 28-104 on a full-frame camera). But the actual focal length of the lens is printed on the front of it: 6.1-30.5mm. At 6mm, it's going to be REALLY hard to get anything out of focus if it's more than a few cm away from the front of the lens. Buck up, though, this is why your P&S also has macro capability--something a dSLR needs a specialized lens to achieve.

You could zoom in, but then your problem will be that your minimum focus distance got longer and you'll have to step back from your subject (increasing your DoF), and your maximum aperture got smaller and went down to f/4.5 (increasing your DoF). So, it's going to be a wash.

Your sensor and lens is roughly one fifth the size of a dSLR's. So, the relative DoF you're going to have at the same exposure settings is going to be five times bigger.

It's just really really tough to get a thin DoF on a small-sensored camera. And this is a feature of P&S cameras, not a fault: nobody wants their point-and-shoot photo to be out of focus. Having a very deep DoF at all times pretty much prevents this from happening.

[ErikUngerPhotography]

Inkista gave you a pretty much perfect answer. The smaller the sensor, the bigger the DOF. The wider the lens, the bigger DOF. Also the closer you focus on your subject the bigger the DOF.

[Fasene]

I have used a Canon G10 for three years now and it will not produce the shallow depth of field you are seeking. Not only that, the nearer you get to producing the background blurring by zooming to telelphoto the more the quality of your image file will suffer. I could regret buying the camera but what's the point in that? Better to use and appreciate its strengths. For the reasons Inkista has detailed plus a couple of others, I can say that what I have in this camera is a high quality, compact landscape/street photography tool with a permanently deep DOF. For optimum quality images I keep the aperture wide open (f/2.8) at all times, use the zoom only at its wide end (28mm) and ensure that there is sufficient contrast (a mixture of bright and dark) in the scene. Any other aperture or zoom settings, or low-contrast conditons inevitably lead to an immediate and noticeable decrease in image file quality from the G10.