Magnification-Factor with VX2100

[J. Stephen McDonald]

The subject of how much magnification the lens of a VX2100 and the other models in its series produces, was discussed last year on this forum. However, I don't believe the exact amount of magnification, based on the 35mm film-equivalent, was ever fully described. I've just gone through the specifications of this camcorder and realized that until today, I've been using some incorrect figures. So I'll list here what I believe are the correct ones. Disregard anything I might have previously stated about the magnification X-power of this model.

The focal length range of the VX2100 lens is 6mm to 72mm. This camcorder has .33-inch CCDs. With the conversion to the 35mm film-equivalent, which is the standard reference used for video cameras, its focal-length range is 43.2mm to 518.4mm. The multiplication factor for this model's conversion is 7.2X. This factor varies according to CCD size. So, the functional focal-length regarding magnification, comes from the combination of a camera's image-sensor and its lens. For cameras with larger CCDs, this conversion factor and the magnification-factor (MF) are both smaller, when fitted with lenses of equal size and power. For example, a camera with a lens that has the same focal-length of 6mm to 72mm, but has a .4-inch CCD, is converted to a 35mm-equivalent by a factor of 6X and this results in a 36mm to 432mm focal-length. You can find this specification for the VX2100 and the 35mm conversion factor on page 163 of its English-language manual.

The 43.2mm to 518.4mm focal-length gives it a 12X zoom range. However, the MF is not as high as 12X. This is because the 43.2mm or wide-angle end of the focal-length, is below the 1X or no-magnification level of 50mm. At 43.2mm, there is a minus-.14X MF. The image at that point is just 86% the size it will reach when the zoom moves up to 50mm. So, at full zoom, the MF of the VX2100 is 10.37X. This is calculated by dividing the top focal-length by 50. It takes 50mm of focal-length for each 1X of magnification power.

Here are the figures for the MF or X-power of magnification when the VX2100 is used with a couple of telextender lens models:

Without added lens-----MF is 10.37X
With Sony VCL-HG1758, a 1.7X Telextender-----MF is 17.63X
With Raynox DCR-2020PRO, a 2.2X Telextender-----MF is 22.8X

One advantage of smaller CCDs, is the greater MF you get from a lens. You also usually get a longer depth-of-focus, when the CCDs are smaller. Sony has done a good job of putting excellent image-quality and low-light capabilities in the VX2100's .33-inch CCDs, which are smaller than those of top-performing models of the past.