Aperture Settings Help

[stripe]

Hello Everyone,

When shooting with my DSLR (D5000), I am usually in aperture priority mode, and I find that I usually shooting wide open (lowest f-stop) if I want to blur background or with it as closed as possible for a lot of depth. I have trouble identifying when I should be getting into the intermediate areas of the aperture range.

I realize that shutter speed is obviously a consideration, so if I am going for a lot of DoF, I am aware of what my shutter speed is (especially when hand holding my camera).

The reason I bring this up is after reading some C&C of some portraits elsewhere on these forums, I am seeing comments like "f/5 may be a bit open for this shot". Is this just a matter of a slightly too shallow DoF, or are there other side-effects that people with keener eyes than mine are spotting?

Thanks!

[Geoff F]

It sounds like you have, more or less, fully understood the aperture/ shutter speed/ISO balancing act.

But selecting the best aperture for those middle range shots requires a lot of expertise; which separates those top grade photographers from the rest of us.

Portraits are particularly tricky. Do you include part of an interesting background or try to totally blur a confusing/contrasting background? Not really a problem in a studio but often a real dilemma for outdoor shots.

The other potential problem with portraits, as you said, is that too shallow a depth of field can, for instance, give one ear in sharp focus and the other a bit blurred.

One other point about aperture is that some lenses are a bit soft when fully open, or too narrow.

But let's see what comments the other members suggest.

[Dave Humphries]

Hi Matt,

If you haven't read it yet, I recommend starting with Sean's tutorial on Depth of Field.

Personally I try to shoot everything at f8 to f11 to get best image quality, as Geoff mentioned, by avoiding the extremes.

However, as you rightly say, if the subject demands a narrow DoF, I'll open up as far as I can (which depending on the lens and the focal length, may only be f5.6) and conversely, if I need more subject in focus, I'll stop down to f16 or f22. I will then adjust the ISO if the shutter speed this gives will risk either camera shake or blur subject movement.

As the DoF tutorial will show, the ratio of camera to subject and subject to background will have a much larger effect on DoF if it can be changed - moving camera closer to subject and using a shorter focal length will vastly improved DoF, but beware of going too close for portraits as it will exagerate perspective and if too close anything closer to the camera than the eyes will take on undue significance, This can result in a large nose, hands or knees and thighs/feet depending upon the pose being adopted by the subject.

Cheers,

[stripe]

Thanks for the help guys. The softness at the aperture extremes is something that I have not really encountered (probably more correct to say something that I do not yet have the eye or experience to notice). I will probably now try and avoid the most extreme aperture settings for my lens, unless they are required.

Thanks again.

[Hans]

Best thing you could do, stripe, is have a look for yourself.

Very crude way I have studied my own lenses is to shoot some news print at various apertures and have a look. Make sure you are on a tripod and in good light so your shutter speed doesn't get too slow for your telephoto length just to make sure, and use the timer or a cable release. You might even want to set the focus to manual and fine tune it before you begin.

Then snap away, moving through in full, half or third stops as you go. Bring them all up in a window and compare. You may not notice too much of a difference by looking at individual photos at 0%, but bring them all up at 100% and look at them together and you will definitely see what you lens is doing at different apertures

Compare the centres of the frames as well as the corners.

Have fun