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Old July 17th, 2004, 01:34 AM   #1
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Camcorders & Lens Power Comparisons

During the discussions following the introduction of the Canon XL2, I and many others learned new things about the true meanings of terms such as "zoom range", "lens magnification", "focal length"
and "angle of view". Despite common belief by non-experts, "zoom range", as expressed by "10X", "16X" or "20X", for examples, is not a measure of lens magnification, but rather of the increase in focal length from the zero zoom position, to full zoom. The lens focal length at full zoom, calculated with the size of the camera's CCD, gives
the amount of magnification, technically called "angle of view". The smaller the angle of view of the lens and the smaller the camera's CCD, the greater the magnification effect will be.

Although camcorder/lens combinations that have higher zoom range "X" numbers, tend to have greater magnification effects, these are different factors and are not synonomous.

I earlier proposed to develop some "MX" numbers, a term I coined, to provide a simple numerical figure, to compare the overall magnification or angle of view that various camcorder/lens combinations produced. The MX numbers give only a relative value, to compare different models. Since the Original Canon A-1 was the first in the line of models that evolved over a 13-year period, to now feature the new XL2, I chose it and its specifications as the standard and gave it an
MX number of 10. All the other models listed below had the A-1 specifications and its MX number used as the baseline for calculating their MX numbers.

To state it more simply, the MX numbers show how much each camcorder/lens magnifies the image, compared to the base number of 10. Since some camcorders have smaller effective image-sensing areas on their CCDs, than the full size of their CDDs, this factor is also part of the calculations. The lens focal lengths given are at full zoom.

Canon A-1: zoom range, 10X; lens focal length, 80mm; CCD size, .5-inch. Result, MX10.

Canon L-1: zoom range, 15X; lens focal length,
120mm; CCD size, .5-inch. Result, MX15.

Sony TR700: zoom range, 10X; lens focal length,
61mm; CCD size, .333-inch. Result, MX11.5.

Sony TRV730: zoom range, 18X, lens focal length,
73.8mm; CCD size, .203-inch. Result, MX19.8.

Sony VX2100: zoom range, 12X; lens focal length,
72mm; CCD size, .333-inch. Result, MX14.1.

Sony EDP10F w/Fujinon Eagle II 77mm lens: zoom range, 16X; lens focal length, 152mm; CCD size,
.666-inch. Result, MX15.

Canon GL1/GL2: zoom range, 20X; lens focal length,
84mm; CCD size, .25-inch. Result, MX21.

Canon XL1/XL1s: zoom range, 16X; lens focal length,
80mm, CCD size, .333-inch. Result, MX16.5.

Canon XL2: zoom range, 20X; lens focal length,
108mm, CCD size, .236-inch. Result, MX28.6.

Note that the TRV730 and the XL2 have smaller effective CCD sensing areas for the 4:3 mode, than the overall CCD size, which increases their MX numbers. The XL1/XL1s are rated with the standard 16X zoom lenses and the XL2 is rated with the new 20X zoom lens. The magnification power of the XL2
with its new lens stands out from that of the XL1/XL1s. If you put the 20X zoom lens on an XL1/XL1s, it would have an MX22.25 rating. I'll repeat the MX numbers below, with only the model numbers, so an easy comparison of their relative magnification powers can be made. The MX for the Sony VX2100 is the same for the VX2000 and the PD150/170.

You can see how varied the MX numbers are for some models, from their zoom range numbers, while these two figures are very close for other models. Anyone could make these same calculations for any other camcorder/lens. If you don't like my system, the basic concept could be implemented in many other ways using different baseline values.

Canon A-1: MX10
Canon L-1: MX15
Sony TR700: MX11.5
Sony TRV730: MX19.8
Sony VX2100: MX14.1
Sony EDP10F: MX15
Canon GL1/GL2: MX21
Canon XL1/XL1s: MX16.5
Canon XL2: MX28.6

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Old July 17th, 2004, 08:19 AM   #2
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Panasonic DVX100A MX Rating

I've calculated one more camcorder to give it a lens magnification (angle of view) rating, according to my MX scale. The Panasonic DVX100A, despite its relatively large, fixed lens, with a 72mm filter diameter, has only a 45mm focal length, at full zoom. With a .333-inch CCD size, this gives it an MX9.38 rating.
Compare this to the MX numbers of other models shown in the previous message. My older Sony TR700 has the same 10X zoom range and CCD size as the DVX100A and has only a 52mm filter diameter, but it has an MX11.5 rating. The smaller lens on the TR700 provides approximately 22% more magnification of the image. This further shows that the zoom ranges and the outer sizes of lenses often don't reveal the amount of magnification they provide to a camera.

Of course, there is more to a good lens system than just reducing the angle of view at full zoom, to give more magnification. For closeup to medium-distance subjects, the lens of the DVX100A could deliver a very good, if not better image than those with longer focal lengths.

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Old July 17th, 2004, 09:06 AM   #3
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Corrections

I made a mistake in copying the focal length for the XL1/XL1S lens, in my earlier message. The focal length of the standard 16X lens used with these models is 88mm at full zoom, not the "80mm" figure I showed on the specifications.
However, I did copy the MX16.5 number correctly for them, so at least I gave the correct result.

Also, I copyed the wrong MX number for the VX2100, which is correctly, MX13.5, not the "MX14.1" I previously showed.

Two more glitches, the TRV730 correctly has an MX22.6, rather than the "MX19.8" I listed previously and the TR700 correctly has an MX11.36, instead of the "MX11.5" I showed. I'll be tighter in my attention to details, next time.

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Old July 17th, 2004, 10:09 AM   #4
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If you really want to know what your magnifications are the following numbers should help. The magnification shown are actual increases in image size.

1/4 inch chip

Focal Length in mm

4mm=1X

8mm=2X

16mm=4x

32mm=8X

64mm=16X

128mm=32X


1/3 inch chip

Focal Length in mm

6mm=1X

12mm=2X

24mm=4X

48mm=8X

96mm=16X

For those with different size chips the normal or 1X magnification is about the diagonal of the chip in millimeters. You can find that information here.

These figures are approximations. Many 35mm photographers will know that a 50mm lens is considered "normal" or 1X magnification. Yet the diagonal of 35mm film is about 42mm.
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Old July 17th, 2004, 11:33 AM   #5
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I'd like to see all camcorder lenses measured in 35mm equivalents.
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Old July 17th, 2004, 06:38 PM   #6
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Jeff, perhaps you could explain further
the meaning of all the figures you give for each size of CCD, on the chart to which you referred, that you first posted last December.

For the 1/4-inch CCD, for example, you show a metric equivalent of 6.35mm, which is correct. This should be a diagonal measurement for a CCD, that is nominally labeled as 1/4-inch. But, next to that, there is a "4.0mm-diagonal" figure and then, "3.2 X 2.4mm, L&W".

I don't understand why the 4.0mm-diagonal and 3.2 X 2.4mm, L&W figures are so much smaller, in this context.

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Old July 17th, 2004, 07:05 PM   #7
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Well, that's another one you just have to know. The vast majority of consumers think a 1/4 inch chip is really 1/4 inch (6.35mm) diagonal. So, it should come as no surprise that a 1/4 inch CCD is actually smaller than 1/4 inch. It's almost 40% smaller. The so-called 1/4 inch chip is actually 1/8 x 3/32 x 5/32 (diag.). The so-called 1/3 inch chip is 3/16 x 9/64 x 15/64 (diag.) The 1/3 inch chip is not even a 1/4 inch (16/64) diagonal.
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Old July 18th, 2004, 12:07 AM   #8
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Jeff, I measured the CCDs on two of my camcorders that have removable lenses.
On my Canon L-1, that has a nominal 1/2-inch (.50-inch) CCD, what appeared to be the active area measured exactly .44-inch, diagonally. On my Sony EDP10F, with two CCDs of nominal 2/3-inch (.666-inch) size, it wasn't so easy to measure them, but I could see the #1 CCD well enough and the active area appeared to be .59-inch, diagonally. In both cases, the active areas measured smaller than the CCDs' nominal size, but not as much smaller as your list indicated. But, perhaps there's an overscanning zone around their margins, that would account for a bit more area that doesn't contribute to the image normally seen on a video screen.

Obviously, to whatever degree the active areas of CCDs are smaller, this would increase the magnification effect on the image.

In any case, determining precise lens and CCD specifications is a complex task, made more difficult by imprecise nominal size references they give to CCDs. I'd bet that there's also been some variations in active size to nominal size ratios, between different manufacturers.

This is one reason I worked up my MX ratings to represent only relative magnification comparisons, between different models and not to be based on any one manufacturer's standards of measurement. If I attribute an MX20 to a camcorder, that just means that in actual use, it magnifies the image twice as much as one with an MX10 rating. The fact that I used the specs of the Canon A-1 as a baseline for comparison, was just an arbitrary selection.

Ideally, MX ratings would be based on field tests and measuring actual image sizes that were reproduced on a screen, rather than using lens and CCD specification numbers, that have dubious precision and uniformity. As soon as I can put a number of different models through an identical field test routine, to determine their magnification power, the MX ratings will be more precise for their intended purpose: model to model comparisons. No amount of calculations or projections, on paper or in a computer, can equal well-conducted field tests, to determine true performance. After doing a uniform field test on them all, CCD sizes and focal length specs can be disregarded, as only measurable results on a screen will count.

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