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aperture +shutter + ios

littleblaksheep
Contributor
Hi, I apologize in advance if this has been discussed.
I can't get my settings right, I'm attempting to take photos with that perfect blur in the back round.
I noticed my aperture doesn't go under 4?
Any advice? My subjects are typically my kids.
Rebel t51
1 ACCEPTED SOLUTION


@littleblaksheep wrote:
Well I have a ef-s 75-300mm lens as well...
I just didn't know of there was like maybe a guide or a general "rule "when using aperture, how much shutter and ios... Does that make sense?

Well, if your goal is to get the most bokeh (blurry background) then the general rule is to always go as wide (lowest aperture number) as you can.   If you're shooting with faster lenses (really wide apertures) then you may not go all the way open for a couple reasons, but with your lenses, open them up.

 

As to the other variables:

  • ISO is an easy one.  Use the lowest ISO you can.  If the photo is too underexposed at your aperture and shutter speed, then you need to raise the ISO.  In general you can be at ISO 100 for outdoors in the sun.  Indoors you're going to have to go higher most the time 400 - 1600 (with a fast lens and decent light - most likely you'll need to go much higher).  Higher ISO = more noise.
  • Shutter speed would be the last variable.  If you know what aperture you want (wide open), you're at ISO 100, then there's only one shutter speed that will give "proper exposure".  If you're unsure, just use Av shooting mode.  Set your Aperture wide open, ISO 100, and see if the camera chooses a shutter speed that freezes the action.  If not, boost the ISO.

Your 75-300 will actually give more bokeh than your kit lens.  You'll have to shoot outside, because you want some space.  Go to a park or something where you can have some nice trees or bushes a good 50 feet in the background.  Use the longest focal length that allows you to still shoot at f/4 - probably only 80 or 90 mm.  And get your subject as close as you can with proper framing.  It's not going to be as blurry as some of the pictures you've probably seen, but at that distance you can get nice results.

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11 REPLIES 11

littleblaksheep
Contributor
Awesome, thank you so much!


@littleblaksheep wrote:
Awesome, thank you so much!

What you have to remember about aperture settings is that the "f/" number is the ratio of the lens's focal length to the diameter of its aperture. So for any given focal length, the larger that number is, the smaller the aperture.

Bob
Philadelphia, Pennsylvania USA
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