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Old Sep 21, 2006, 6:19 AM   #1
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Sorry for starting two threads in a row. :-) (I need to release those disturbing questionsconcerning background blurring issues as well)

Is a F/2.8 and F/3.5 zoom lens on a APS-C size image sensorcapable of blurring background without using "cheating" macro mode? (Means; I want to blur a portrait's background in reality)

Is a wider angle lens set at F/2.8 aperture having less ability to blur a background than a telephoto lensset atthe same F/2.8 aperture?(All on a APS-C imager)

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Old Sep 21, 2006, 8:22 AM   #2
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Go to this link to see it illustrated.


Firstly select one of the 1.5 crop sensor cameras, any of the Nikon DSLRs will do.

Then look at the chart for a focal length of say 25mm. Then change that to 250mm and compare.

The actual relationship is moderately complicated, the website above has the equations so you can get a more detailed idea. It's quite difficult to put precisely into words, you really need to look at the equation to understand it.

But if you just want to develop some good photographic rules-of-thumb then those charts are a very good place to start.

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Old Sep 21, 2006, 9:24 AM   #3
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Three things to do if you want to get background out of focus:

1) Use a large aperture
2) Focus close
3) Use a longer lens

DOF talbes and calculators will show that numerically.
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Old Sep 21, 2006, 9:48 AM   #4
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Alright, thanks for clarifying.

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Old Sep 21, 2006, 7:51 PM   #5
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The "modes" of a DSLR do not "create" the effects that you are after, such as out of focus backgrounds. The modes will not make the camera do things beyond what the camera is capable of. These modes only select the "best" settings for the mode you have chosen, which may or may not give you the effect you want, or even be the best settings for the situation. The camera uses settings based on an estimation of what usually works best. For example, for macro, typically smaller aperatures are used to create more DOF to insure your whole subject is in focus as DOF is razor thin at close distances. This may or may not give you the blurred background to the degree you desire. In other words, the camera will not create a blurred background when the camera settings will not allow it. These so called "idiot proof" modes are no substitute for learning the ins and outs of exposure and how aperature, iso, and shutter speed affect it, as well as how the image will appear.
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