Depth of field question

[brandname]

Every picture I take looks like the background is out of focus. I believe this is due to the Fstop(depth of field) What if I want to focus on both the forgound and background at the same time. Do I have to set the aperture f5 or something like f18 and then lower the shutter speed? I alos heard that lenses higher than 50mm have no DOF.

Any help would be great. It looks like the camera is already preset to focus on the subject and nothing behind.

[akysiev]

Yes you would want to lower your aperture to increase depth of field. Either that or move away from the subject or decrease your focal length. All focal lengths have depth of field except that it is just not as pronounced with longer focal lengths due to its direct relationship to depth of field. So you can compensate for longer focal lengths by stopping down or moving away, but there's no point to moving away due to compositional reasons. Thus, effectively, aperture is the only way you can control depth of field in an already-composed shot.

I wrote a quite lengthy post about depth of field and hyperfocal points that you might want to check out. Here's the link: http://www.dcresource.com/forums/showthread.php?t=11403

[jazzboybenny]

I have only recently started messing around with the DOF field settings on my camera to achieve the blurring background effect. I manage to achieve this most of the time, so thought about using the same technique in the garden, photgraphing insects such as snails and caterpillars...only to discover that in most cases the background is in focus and the insect is blurred.
Is this because I am too close to the subject? Is using Macro mode recommended?
any help most appreciated.

[val123]

I have only recently started messing around with the DOF field settings on my camera to achieve the blurring background effect. I manage to achieve this most of the time, so thought about using the same technique in the garden, photgraphing insects such as snails and caterpillars...only to discover that in most cases the background is in focus and the insect is blurred.
Is this because I am too close to the subject? Is using Macro mode recommended?
any help most appreciated.

I would definately use macro mode if trying to get close up pictures of insects etc.

[brandname]

for insects I get great shots even with 70-300 lense using manual focus. Autofocus gets confused so I trust my self more on small subjects.

[akysiev]

jazzboy, if you believe that you are focusing properly, it is most likely related to your near focus limit. I forget the actual formula for it but to solve this problem, you simply have to move away. However, zooming in afterwards negates the moving backwards I believe, or at least it does to some extent.

[Dave Dilks]

akysiev, that Depth of Field calculator you provided in your link was really enlightening. For my ultra-zoom (400mm) camera at f2.8 and objects 50-100 feet away, the depth of field is only a few inches. :eek: I often use similar settings for concert photography, and had assumed the subjects were far enough away to provide plenty of depth of field. Now understand why they are sometime only partially in focus. Thanks.

[Warin]

akysiev, that Depth of Field calculator you provided in your link was really enlightening. For my ultra-zoom (400mm) camera at f2.8 and objects 50-100 feet away, the depth of field is only a few inches. :eek: I often use similar settings for concert photography, and had assumed the subjects were far enough away to provide plenty of depth of field. Now understand why they are sometime only partially in focus. Thanks.

Make certain you enter all the corect variables. ie: Focal length on a large zoom camera (like say an F20) is quite different than 35mm.

For example:


At full zoom (35mm equivalent of ~420mm), the FZ20 has a focal length of 72mm. The depth of field will give clear focus at that zoom from 70.6 to 80.0 feet at 75 feet. Everything within 9.4 feet will be withing focus, at f/2.8. So I am not sure how you came up with a rating of several inches.

[Dave Dilks]

Make certain you enter all the corect variables. ie: Focal length on a large zoom camera (like say an F20) is quite different than 35mm.

For example:


At full zoom (35mm equivalent of ~420mm), the FZ20 has a focal length of 72mm. The depth of field will give clear focus at that zoom from 70.6 to 80.0 feet at 75 feet. Everything within 9.4 feet will be withing focus, at f/2.8. So I am not sure how you came up with a rating of several inches.

You're right, I was using the wrong focal length in those calculations. That leaves the only explanation of my partially in focus pictures as ..... User Error?

[Warin]

You're right, I was using the wrong focal length in those calculations. That leaves the only explanation of my partially in focus pictures as ..... User Error?

I am going to vote a little user error and a little circumstance. It is quite possible that you are right on the edge of the focus area. I would recommend kicking it over into manual focus. What camera are you using? at that zoom with a 2.8 aperature, it almost has to be the FZ20 from Panasonic. If so, turn focus assist on and use that trick focus ring.

[akysiev]

I would lean more towards focus error here. In general concerts have dimmer light and at such extreme distances (unless you're front row trying to take a photograph of a button on a performer's shirt with that 400mm :D), that might fool your autofocus. As Warin said, kick it into manual to fine tune and be sure.