Aperture help please

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Aperture help please

Postby Packnutsmom+1 » Fri Apr 23, 2010 12:13 pm

I am slowly learning my manual setting and then come to find out there is soo much more than just shutter speed :oops: Anyways, for the aperture ( on my camera it's F) the smaller it is (say 5.3) does this cause the background to be more blurry while the thing closest to the lens is in focus/clear and the larger you go causes the closest things to be out of focus and the things far away clear?

Also, I noticed when I changed my aperture, my shutter speed had to be re adjusted is this correct?
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Re: Aperture help please

Postby blue-eden » Fri Apr 23, 2010 12:23 pm

Packnutsmom+1 wrote:I am slowly learning my manual setting and then come to find out there is soo much more than just shutter speed :oops: Anyways, for the aperture ( on my camera it's F) the smaller it is (say 5.3) does this cause the background to be more blurry while the thing closest to the lens is in focus/clear and the larger you go causes the closest things to be out of focus and the things far away clear?

Also, I noticed when I changed my aperture, my shutter speed had to be re adjusted is this correct?


The bigger the aperture (the smaller the number), the smaller the plane that will be in focus. It depends on WHERE you focus. You can determine this using a Depth of Field calculator.

http://www.dofmaster.com/dofjs.html

So if you focus on something, whatever is in that plane, within the range and depending on how far away from your subject, will be in focus. The further you are away from your subject, the more that will be in focus, generally. The closer you are to your subject, the less will be in focus (and also the greater the chance to miss focus, too, because the plane is so narrow) This is why macro lenses, when used wide open, have a VERY very narrow DOF and it's very hard to get what you want in focus if you are close up as well.

The smaller your aperature, the greater the plane that is in focus, so most of the picture would be in focus, including the background.

Because you are widening or narrowing how wide it's open (letting in more or less light) to keep the exposure where you want it, you'll have to change your shutter speed (how long it's kept open) to accommodate the amount of light coming in.

ETA - just using your example of an Fstop of 5.3, this is actually not very wide open. I would consider anything from about F1.2-3.5 to be wide open (VERY blurry backgrounds if focusing on something in the foreground). From about 4-8 (and 8 is pushing it) is middle, and you'll have blur if you shoot very close up, but not if you shoot from a distance. From F8-32 is narrow, and most of the picture would be in focus.
My preferred ap is F2.

Here is a snapshot example of one taken at F2 (if I can recall correctly, I had to change quite often in this light), from a slight distance.
See how the background is still pretty much in focus?

Please excuse the poor quality shot, this was shot for the purpose of using it as a template for a small mentoring group to do plays with, and it's straight out of the camera, no editing or sharpening at all.

Image

Because she's pretty far from me (I used a 50 mm lens) the b/g has good focus.

Here is another one, also at F2.

Image

The background is more blurred, and there is bokeh because of the light in the back.

And another using the macro lens, very wide open.

Image

Background completely blurred, because the background is VERY far away, on top of me being very close to the flower.

I hope this helps!
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