How to use Aperture and DOF effectively

[michael_antoi]

I just picked up my lens (24-85 USM) and a cheap dslr (Canon D30)

I'm trying to figure out how to creat blurred backgrounds.


Been playing around a fair bit and this is the best I could come up with

Unfortunately I have no idea how i did it..

Any help would be great

thanks guys

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[MattC]

Hi,

There are three main things that affect DOF. Aperture, Distance and Focal length.

1. Aperture. The larger the aperture (smaller f) for a given distance and focal length, then the smaller the DOF.

2. Focal Length. The longer the focal length for a given distance and aperture, then the smaller DOF.

3. Distance. The closer to the subject with all else equal, then the smaller the DOF. There is also the effect of distance of the subject to the background and its ratio with lens to subject distance. The higher the ratio (subject to background / lens to subject) then the more OOF the background will be.

Large aperture lenses like the 85/1.4 lens (or the much more affordable 50/1.8 ) can produce those sought after blurred backgrounds fairly easily. With slower lenses it can be neccesary to work at it by closing up the distance to subject, picking an angle with a far background and using a longer focal length. This may not leave a lot of room for framing a person, but it is good for other smaller things.

There are plenty of online DOF calculators around that will give you an idea of the relationships and what to expect with different combinations of distance, aperture and focal length.... or you can use this one http://www.pixspot.com/albums/userpics/ ... ulator.xls

Then go out and play

Cheers

[macka]

I found the tutorials on http://www.luminous-landscape.com invaluable when I was first trying to understand these aspects of photography.

[michael_antoi]

i was wondering if anyone had pictures comparing the bokeh between say a 50mm f1.8 to a 24-85mm f3.5

[ozonejunkie]

I don't know of anyone that has the 24-85 on this forum. I have the 28-105 3.5-4.5, and have taken a couple test shots for you.

28-105, 50mm@f4



50/1.8@1.8



I hope this helps.

Tristan

[Sheila Smart]

Here's one taken with my 50mm f/1.8 at f/4.5. I sold this lens with my 20D as I rarely used it, although its a super sharp cheapie.

http://www.pbase.com/sheila/image/37816813

Cheers
Sheila