What good is aperture on a G11?

[kezug]

What good is the aperture on a camera like the G11?

While the amount of light can be controlled with Av...It seems that the focal length or dof is pretty much the same regardless of the aperture setting. Especially if shooting a subject from 10 feet or more away. So at that distance, on a camera like this...Aperture is really only good for controlling light, right?

Am I missing something here?

[kezug]

bump :oops:

[NOsquid]

That's mostly correct.

[denncald]

There is also the diffraction issue. I try to shoot around f/4.0 on my G9 to keep it in the sweet spot for image sharpness. It may be about the same f stop for the G11.

http://www.bobatkins.com/photography/digital/canon_powershot_g11_review4.html

Dennis

[athrasher]

I generally stay between f/2.8 and f/8.0.

[JeffreyG]

If you are using f/2.8 on a sensor the size of the G11's, you are getting the same DOF that you would get on a 135 format (35mm film) at f/14 (4 and 2/3 stops more).

So if you think about this in 35mm terms, supposing you had a 28-120 f/14 zoom lens, how often would you really ever stop down the lens? Probably close to never.

So the OP's supposition is right - for anything other than macro the G11 is likely to have plenty of DOF wide open for most uses. There are probably few good reasons to stop down in most circumstances.

[Tom Reichner]

I don't understand - why wouldn't the aperture setting have the same effect on DOF that it does on an SLR?

[JeffreyG]

I don't understand - why wouldn't the aperture setting have the same effect on DOF that it does on an SLR?

It does have the same effect, but wide open the G11 is already at a point where the DOF is quite large and the lens is on the verge of diffraction softening.

Most dSLR lenses wide open have very thin DOF. As you stop down you pass through a large range where DOF grows from thin to medium to large and eventually you get to where diffraction starts to affect the image.

On the G11, you start all the way up where DOF is huge (it's like f/14 on a 5D). There are precious few situations where I use apertures smaller than f/14 on my 5D, so I would almost never stop down a G11 lens.

[John Baker]

As pointed out the aperture works the same on all cameras; it is basically used to balance the light to achieve an exposure, the other two elements which control are the shutter speed and the ISO. While one of the main roles of the aperture as pointed out is to work with, and give some control to the Depth of Field, I would agree it is not so much of an issue when using the camera for normal photography. But it can be very useful to be able to adjust the aperture to bring down your shutter speed to get various effects, so for example if you want to get aircraft propellers with a bit of movement, or helicopters you need a shutter speed of around 1/125” go much faster and you will freeze the action, which does not look good. Opening up the aperture will also extend the range of your flash, as each extra stop adds about 1.4x to the range – the camera has settings from f2.8 through to f8 or 4 stops of light (f2.8 – f4 – f5.6 and f8 ).

If you do close up work the aperture becomes really important to make the most of the limited Depth of Field – a couple of examples of a Crane Fly from today.

1 - Standard shot, taken at the wide setting and using the close focus, fairly good Depth of Field, you can make out what is in the background - not a major problem.
http://www.jfbclick.com/images/10-03KillBugs/AIMG_1710.jpg

Put a +2 dioptre close up lens on the camera and the DoF starts to shrink, this is taken at f8 - background is out of focus
http://www.jfbclick.com/images/10-03KillBugs/AIMG_1707.jpg

Change to a +4 dioptre and the DoF now does not extend from wing tip to wing tip - still at f8 - opening up the lens would reduce the DoF even further...
http://www.jfbclick.com/images/10-03KillBugs/AIMG_1719.jpg

Putting both the +4 and the +2 together gives a +6 dioptre effect - again at f8 the DoF has shrunk again, while this is not perfect, but it shows how restricted the DoF can become and how important it is to control the effects it can give.
http://www.jfbclick.com/images/10-03KillBugs/AIMG_1748.jpg