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Video Performance* (8.0)*
The JVC GZ-HD7 features three 1/5" CCDs, each featuring a gross pixel count of 570,000 (an approximate effective pixel count of 530,000). The camcorder, like many three-chip models, uses pixel shifting to increase the effective resolution, off-setting one of the chips by a half a pixel’s X and Y axes. In this case, the recorded image resolution is approximately 2032 x 1116, or an effective resolution of 1952 x 1096. Each pixel on the CCDs measures 3.28 x 2.28 microns, approximately two times the sizes of JVC’s 2MP standard definition GZ-MG77.
And now what you’ve all been waiting for… let’s take a look at the GZ-HD7’s performance. Overall, we have come to one conclusion: this JVC MPEG-2 transport stream is not as good as the best HDV performances. But neither did it suffer the worst parts of the AVCHD camcorders, which is the trailing and noise issues. The JVC GZ-HD7 is the middle ground.
Video compression formats often show their merits in how they deal with motion. In good light, the GZ-HD7 has a decent picture. Retaining detail in motion, even a slower motion, is difficult. You have an immediate sense of where the I-frames are versus the frames that the camcorder is trying to interpret. To its credit, we did not see a stuttering effect, which was very noticeable in the Panasonic HDC-SD1. Both the GZ-HD7 and the AVCHD camcorders displayed ghostly trails from moving objects, but they were more noticeable in the AVCHD models. That said, in a side-by-side comparison, the Canon HV20 and Sony HDR-HC7 (both HDV) produced much smoother motion and retained more detail in pans and tilts. HDV compression wins this portion of the performance hands down.
The overall image quality was not aided by the fact that the GZ-HD7’s image looks noisy, cutting back on apparent sharpness. A combination of both noise and compression artifacts, the grain is extremely coarse, reminiscent of a 16mm film. No particular portion of the dynamic range appeared more affected than the another. This was not the case in competing camcorders. The Panasonic HDC-SD1 and HDC-DX1 showed most of their noise in the middle greys, and the Sony AVCHD camcorders showed more noise in the blacks.
At an even 3000 lux, the GZ-HD7’s image showed a relatively even, saturated color performance. Because this is aimed at a the consumer market, it’s hard to fault it too much for oversaturation. This is something the consumer want, and JVC is delivering. ¬The GZ-HD7 is certainly the most saturated of all the HD camcorders this year, however, something that even occasional use consumers should consider. We prefer the Canon HV20 for color performance, though many may prefer the Sony HD7, which has a bolder, darker color palette. During shooting, the JVC GZ-HD7’s colors look like they’re bleeding, often the price of oversaturation.
The GZ-HD7 offers one performance tweak that users might find helpful. The sharpness control works just as it says. With a +5 setting (the highest), the image appears as though it ran through a Photoshop sharpening a few hundred percent. With a -5 setting (the lowest), the image looks out of focus. These extremes go too far for good-looking video, so shooters will want to tread lightly with the control, limiting it to +/-2.
Overall, we have to place the cumulative video performance score in the same range as the AVCHD camcorders we’ve seen this year. While the motion artifacting is better, the fat-grain noise and bleeding colors take their toll. The first generation codec HD Everio needs some work.
Video Resolution* (13.125)*
We gauge video resolution by shooting a DSC Labs video resolution chart and viewing the image on an HD monitor. As we found in the video performance, the HD7 seems to be the middle ground between AVCHD and HDV. The horizontal resolution measured approximately 525 line widths per picture height (lw/ph) and vertical resolution measured 500 lw/ph.
The low light performance is truly a mixed bag. One problem is that the GZ-HD7 does not have much in the way of dynamic range. Its tendency to blow out whites and bottom out on shadows is obvious when you shoot indoors. If the scene is a fixed, even lighting, like our color chart at 60 lux, the HD7 can produce a good luminance (with auto gain control, AGC, on). Here, the oversaturation that we criticized in bright light becomes something of an asset. But other problems become apparent. The noise levels are very high, higher than the Panasonic HDC-SD1 and HDC-DX1. As we said before, the noise is not of a fine grain that could be ignored. This is big, fat noise. For all JVC’s hype about having great noise reduction, we’re just not seeing it here.
Fortunately, the camcorder has a great set of manual controls, including independent aperture and shutter control, as well as the ability to turn the auto gain on and off. At 60 lux, the aperture was already maxed out at f/1.9 (in telephoto). Lowering the shutter speed to 1/30th had an unexpected effect, however. Normally, this would brighten the image. In the case of the GZ-HD7, lowering the shutter speed from 1/60th to 1/30th seemed to prompt the camcorder into decreasing the gain – so much so that the 1/30th image is actually darker than the 1/60th image. Overall, it looks better; the colors appear richer without overexposing.
The JVC GZ-HD7 also offers a brightness control, a +/-6 increment EV scale. To show you how bright it gets, the image here is set to +6. As you can see, the image is far too overexposed.
You can, as mentioned, turn the AGC off, but you won’t like the image; it’s very dark.
At 15 lux with the AGC on, the noise becomes severe. A fair level of detail is retained, however, merely by the fact that this is HD. A standard definition camcorder with this much noise would prove unusable. The colors remain fairly good.
Adjusted to a 1/30th shutter speed, the image looks a good deal better, though even a manual white balance leaves the image too blue.
The brightness control did nothing at this light level. Whatever settings "bright" draws from – aperture, shutter speed, gain – have been exhausted.
At 15 lux with the AGC off, there is no image to speak of.
The GZ-HD7 was capable of producing 50 IRE at 17 lux, not quite as good as the Panasonic AVCHD camcorders. This sensitivity could not hold a candle to either the Canon HV20 or Sony HDR-HC7. According to Imatest, the picture had a color error of 8.93, 0.9025% noise, and a saturation of 94.04% (out of an accurate 100%).
The JVC GZ-HD7 is equipped with an optical image stabilization, or OIS system, to reduce the effects of camcorder shake on recorded video. OIS stabilizes the image by physically isolating the lens element from the camcorder body, sometimes using gyroscopes or motors. As a remedy for hand shake, OIS systems generally work well, without reducing video resolution when enabled. The other more common (and cheaper) stabilization system is EIS (electronic image stabilization). EIS reduces vibration by generating a digital buffer around the margins of the frame, and unlike OIS, reduces the resolution of recorded video. OIS systems tend to be found on higher-end camcorders like the HD7, and are the better of the two stabilizations methods. We tested the HD7's OIS system using our camcorder shake emulator, custom built for Camcorderinfo.com. The shake emulator can be adjusted to produce movements at differing intensities and frequencies. We tested the HD7 at Speed 1, equivalent to the shake produced while holding a camcorder and standing still; and Speed 2, equivalent to the more intense shake of a moving vehicle. The JVC HD7’s OIS system reduced recorded image shake by approximately 75% at Speed 1, and 50% at Speed 2. We derived these calculations by measuring the motion difference between footage shot with OIS off, and OIS on. While this score was good, the Panasonic HDC-SD1 still remains king of the shake correction this year.
Wide Angle* (10.4)*
We measure the field of view of camcorders in 16:9 mode. The zoom is set to its widest angle, image stabilization is turned off, and we view the full video frame on an external monitor derive a field of view measurement. The JVC GZ-HD7's maximum field of view was 52 degrees.
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