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View Full Version : What effects depth of field THE MOST?



jcanon701
12-26-2007, 06:07 PM
So i've been studying/reading about photography. These are the three main variables that effect depth of field:

- Aperture
- Changing distance between camera and subject
- Changing the lens

My question is = Which of those 3 variables effects depth of field THE MOST?

I was struggling with this because I was stuck between using NO ZOOM + BEING CLOSER vs ZOOM + BEING FARTHER to get a LARGE DOF.

I'm asking this because it seems like one variable cancels out the other.

For example:
- Using a short lens gives more DOF, but being closer gives less DOF - so they cancel each other out.
- On ther other hand, using a long lens (zoom) gives less DOF, but being farther gives more DOF - so they cancel each other out also.

It seems to me that distance from the subject alters DOF the most, but can someone clarify this for me? thanks!! (i hope i didn't confuse anyone)

The Mangler
12-26-2007, 07:36 PM
So i've been studying/reading about photography. These are the three main variables that effect depth of field:

- Aperture
- Changing distance between camera and subject
- Changing the lens

My question is = Which of those 3 variables effects depth of field THE MOST?
I would say aperture, and a lot of the time it's the only one you actually have control over.


I'm asking this because it seems like one variable cancels out the other.

For example:
- Using a short lens gives more DOF, but being closer gives less DOF - so they cancel each other out.
- On ther other hand, using a long lens (zoom) gives less DOF, but being farther gives more DOF - so they cancel each other out also.
Not quite... The distance you need to think about is the distance from your subject to the background/other objects - Not the distance from subject to you.

If your subject is close and the background is far, the background will be blurred. If your subject and background are both the same distance (near or far), or close to it, they will both be in focus. How much separation your subject & background need will depend on what aperture you're using.

Put your camera into aperture priority mode (Av on Canon) and set it to the max aperture (smallest number). Focus on something and hold down the DOF preview button while you roll the wheel & stop down the aperture. You'll see pretty quick how much aperture affects DOF.

jcanon701
12-28-2007, 10:53 PM
after some experimenting and reviewing of the pictures i took it seems like DOF is effected almost equally by both the length of the lens + the distance from camera to subject.

Aperture effects it A LOT also, BUT a change in aperture using a short lens changes the DOF much more vs changing the aperture using a long lens/being close to the subject

Summary:

- DOF is almost equally effected by: distance from subject to camera + length of lens
- The deciding factor is the use of aperture because the effect of aperture on DOF is greater when using a wider lens vs using a long lens/being close to the subject (which is almost the same thing)

After this experimenting I also understand why people use long lenses for portrait work now because it throws the background out of focus AND it makes the background simpler which gives more attention to the subject.

So I guess when using a lens like my Sigma 18-50mm f/2.8 lens, I would use the wider end when I want to complement the subject with objects in the fore/background VS. using the longer end when I want to really hone in on a subject, effectively throw the background out of focus (not that i can't with the wider end, but it's just easier right?), and make the background simpler to emphasize the subject.

Am I getting everything right here? i've read tons of articles online about photography but i don't think i've ever stumbled onto something as specific as i described it (well.. it's rare since most articles are rather general).

Or did I just totally get everything wrong? please correct me if i did.