snodart
Veteran
I know that Barry has touched on this, but I saw the question pop up again. I have been working on the Snod35 DIY DVD/kit which covers this topic so I figured that I would go ahead and post this. A sales pitch? Maybe.
The reason that 1/3” CCD cameras are limited to a long DOF:
The target size is the size of the physical element that is capturing and recording the image in a given camera. In a motion-picture film camera, it relates to the size of the film. With a DV camera, the target size is the size of the CCD(s) that are recording the image and converting that information into a digital signal. In the case of most miniDV cameras, including the Panasonic dvx-100, the CCD is 1/3". 1/3” does not reflect the actual physical size of the sensor however. The actual width of a 1/3” CCD is somewhere around 5mm wide. Likewise, most 35mm film does not actually have a frame size of 35mm since some of the space is taken up by the perforations in the film and by soundtrack information. The actual frame width of 35mm is often closer to 22mm. So from this, we see that the target size of the 1/3” CCD camera is about 4 ½ times smaller than the actual frame size of 35mm film.
What does this mean exactly? Let’s say we are using a lens with a focal length of 50mm for a 35mm film camera and for a 1/3” CCD camera; both of which are at the same distance from the subject.. The images below show how much of the subject each would see.
So, in order for the 1/3" CCD to achieve the same subject size in relation to the frame, we would need to do one of two things… either move the camera way back until the subject size is the same in relation to the frame (as compared to the 35mm frame), or use a lens with a shorter focal length. Always shooting from a great distance is not a very practical solution (and technically it lengthens the DOF anyway), so the better option is to use a shorter focal length lens. This would increase our field of view and allow us to obtain the same subject size within the frame... from the same distance as the 35mm camera (or a comparable distance anyway)..
This is why prosumer DV cameras have considerably short focal lengths. The Panasonic DVX100B for example has a zoom lens that ranges in focal length from 4.5mm to 45mm. Having a shorter focal length essentially compensates for the very small target size. Since a short focal length inherently creates a long DOF, 1/3” DV cams are limited to a long DOF.
You can always back the camera up and zoom all the way in so that the focal length of the DVX is at 45mm. Though technically the DOF would be the same, visually it appears to be much shorter. The reason for this is an whole other can of worms...
The reason that 1/3” CCD cameras are limited to a long DOF:
The target size is the size of the physical element that is capturing and recording the image in a given camera. In a motion-picture film camera, it relates to the size of the film. With a DV camera, the target size is the size of the CCD(s) that are recording the image and converting that information into a digital signal. In the case of most miniDV cameras, including the Panasonic dvx-100, the CCD is 1/3". 1/3” does not reflect the actual physical size of the sensor however. The actual width of a 1/3” CCD is somewhere around 5mm wide. Likewise, most 35mm film does not actually have a frame size of 35mm since some of the space is taken up by the perforations in the film and by soundtrack information. The actual frame width of 35mm is often closer to 22mm. So from this, we see that the target size of the 1/3” CCD camera is about 4 ½ times smaller than the actual frame size of 35mm film.
What does this mean exactly? Let’s say we are using a lens with a focal length of 50mm for a 35mm film camera and for a 1/3” CCD camera; both of which are at the same distance from the subject.. The images below show how much of the subject each would see.
So, in order for the 1/3" CCD to achieve the same subject size in relation to the frame, we would need to do one of two things… either move the camera way back until the subject size is the same in relation to the frame (as compared to the 35mm frame), or use a lens with a shorter focal length. Always shooting from a great distance is not a very practical solution (and technically it lengthens the DOF anyway), so the better option is to use a shorter focal length lens. This would increase our field of view and allow us to obtain the same subject size within the frame... from the same distance as the 35mm camera (or a comparable distance anyway)..
This is why prosumer DV cameras have considerably short focal lengths. The Panasonic DVX100B for example has a zoom lens that ranges in focal length from 4.5mm to 45mm. Having a shorter focal length essentially compensates for the very small target size. Since a short focal length inherently creates a long DOF, 1/3” DV cams are limited to a long DOF.
You can always back the camera up and zoom all the way in so that the focal length of the DVX is at 45mm. Though technically the DOF would be the same, visually it appears to be much shorter. The reason for this is an whole other can of worms...
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