Depth of field

[Rob100]

Hi,

Does anyone have any tips to improve the depth of field?

I've tried my camcorders portrait mode but it doesn't do much. I do have adjustable f-stops on this camera (Panasonic MX-300B), but I found that this just let more light in so I had to speed the shutter up to compensate. I bought a ND2 neutral density filter and this helps (a little), but the background is still too much in focus. Is a ND4 darker than a ND2? By keeping a greater distance from the subject and zooming in (optical only of course!) helps, but this does start to limit me to tripod only.

Any advice would be appreciated.

Thanks,


Rob

[Flying dutchman]

!!!???? As far as I know, it should help to move in closer to your subject and zoom out (rather than to move away and zoom in) if you want to make the background less sharp.

Does your camera have a "sports" program (=highest shutter speed, a.k.a. large diaphragm) ?

[Rob100]

Hmm, that seems to contradict the manual for and my tests with my digi still camera (Canon G2).

The NV-MX300B has both a sports and portrait mode, but also has total manual control over the apature and shutter.

Rob.

[Luco]

Depth of field is related to the focal lenght of the lense in conjonction with the F-stop.. the fastest you can get will help your DOF so more light is needed , or film speed (when shooting with film), and also, most of it is done with a stand-alone lense and not with a zoom...

http://www.outsight.com/hyperfocal.html#ref

"OO"

[Dr Mordrid]

Exactly.

The ability to adjust DOF depends on having decent manual settings in your camera OR some advanced program options. As noted increased DOF field requires a small apature (f-stop) and/or long focal length.

Absent the small apature option using a telephoto setting with the camera at some distance from the subject will give an increase in DOF, but this isn't always an option....particularly in close quarters.

Increasing the lighting level can make the the cam close the apature and thereby increase the DOF, but this too can be tricky.

Now....more DOF isn't always a good thing. A decrease in DOF can be useful when doing keyed effects in that if you focus on the subject it'll blur the background. This makes lighting imperfections blend into the rest of the background and eliminates most imperfections in the background itself, all of which aids the key.

A decrease in DOF can also be useful when the background distracts from the subject. Causing the background to blur can be used to bring the viewers attention back to where it belongs.

Dr. Mordrid

[Flying dutchman]

Doc, if I'm not mistaken, Rob100 wanted to DEcrease the sharpness of the background. So IMHO he needs a larger aperture (which can, for instance, be obtained with a sports program, which selects a super fast shutter and compensates the loss of light with a large aperture).

His observation that zooming-in blurs the background is correct, but IMHO for a different reason: Most zoom lenses simply enlarge the center part of the wide-angle view. Because of this, less light hits the CCD. So a larger aperture is chosen by the camera. The same result can be reached with the aforementioned sports program.

Using a wide angle lens at a shorter distance has the logical side-effect that the background is _relatively_ further away and thus becomes somewhat out of focus.

[Rob100]

Hi,

Thanks for the replies. Just to clarify.... Sorry if I didn't make myself clear...

The effect that I'm trying to achieve is so that if for example I am filming a couple talking (lets say out in the park) that they stay focused, but other people in the background are blurred as not to distract you by drawing your attention to what's going on behind. Or another example would be filming a flower and everything else in the garden (or flowerbed depending on the angle) is blurred, thus making the flower you are looking at stand out.

When taking stills I have achieved this no problem with my digi stills camera by adjusting the apature manually or even using the inbuilt program mode for "portrait".

The NV-MX300B gives me the following manual control (according to manual - camera is downstairs ATM):

Apature/Iris: F16 - F1.7 (plus when fully open 0db - 18gb gain)
Shutter speed: 1/50s - 1/8000s

Thanks,


Rob.

[Dr Mordrid]

A neutral density filters value isn't linear to its numeric designation. ND exposure change in stops;

ND2 = 1 stop less exposure
ND4 = 2 stops less exposure
ND 8 = 3 stops less exposure
etc.
etc.

Dr. Mordrid

[Luco]

to achieve what you need , you should use a small focal lense... and a small f-stop... the main prob with zoom lenses are that they are "compressing" images..... or layers if you prefer....
use a black flag..... or underexpose the background....
or get behind the depth's limits.....
cheating the subject distance can be an option also...
the professionnal option could be also to use the "rack focus" on an hand-held cam technique but you'll need an assistant... (guessing that you are shooting a moving scene...)

http://www.kodak.com/cluster/global/en/consumer/pictureTaking/cameraCare/cameCar6.shtml

"OO"