Video Accessories Misc
- Written by John E. Johnson, Jr.
- Published on 16 November 2009
- JVC GZ-HM400U High Definition Video Camera
- Page 2: The Design of the JVC GZ-HM400U High Definition Video Camera
- Page 3: The JVC GZ-HM400U High Definition Video Camera In Use
- Page 4: The JVC GZ-HM400U High Definition Video Camera On the Bench
- Page 5: Conclusions About the JVC GZ-HM400U High Definition Video Camera
- All Pages
On the Bench
Cameras that I tested some time ago tended to have significant falloff, but the JVC is very good in this regard. In wide angle, the worst falloff was only 0.113 f-stops, and in telephoto, 0.311 f-stops. This is excellent lens performance.
Resolution (sharpness) results are shown below. The MTF-50 value was 0.494 cycles/pixel, or 1067 LW/PH. The theoretical limit is 0.5 cycles per pixel and 1080 LW/PH, so this is very close, and certainly the best I have seen in any video camera I have tested. These numbers can go higher than the theoretical limit if there is a large amount of sharpening added by the camera's video processing circuitry, and the "hump" in the black line near the top of the graph midway across the graph indicates some sharpening has been applied.
Keep in mind these data represent the visible lines at 50% contrast. The "perfect" camera would have an MTF-100 value of 1080 LW/PH, meaning 1080 lines going horizontally across the screen at 100% contrast (absolute black lines adjacent to absolute white lines). We may now need to raise the bar for the tests to MTF-75.
Chromatic aberration was 0.629 pixels, not the best I have seen, but certainly not the worst.
The gray scale test results (below) indicate that the camera subdues the whites at the upper end of the scale. This prevents highlight blowout. The video noise level was about average, and because it is nearly the same across the various brightness levels, but does rise slightly at the darkest zones, I would think that a low amount of noise reduction is being applied.
The Kodak Q-60 color target had the colors right, but was a bit underexposed.
The Gretag color test chart showed over-saturation, and also was a bit over-exposed.
A different chart analysis of the Gretag test pattern (a series of color chips) shows the over-saturation in some of the colors, as the circles (representing the way the camera reproduced a specific color) are more towards the outside of where the reference colors are located (squares). White is at the center of the chart. Maximum saturation for a specific color is at the periphery of the chart.