数码相机审裁处

One of the key purchasing decisions when setting up a streaming production studio is the choice of camera. Since most streaming today is done at a resolution of 320x240 pixels, 即使是高端的, some people are questioning whether or not it is worth the extra $1,000 or so to purchase a "prosumer" camera whose better video quality will ultimately be "dumbed down" for delivery.

To get to the bottom of the issue, we compared two prosumer DV cameras with a much lower-cost consumer camera. 索尼的DCR-VX2000, 标价为2美元,999, 以及佳能的GL1, 售价2499美元, are both three-CCD units. Canon’s Elura 2mc is a single-CCD, very compact camera with a much lower list price of $1599.

Note: Because LCD size, 电池寿命, and other "cool" features don’t generally affect the actual quality of audio and video produced by a DV camera, we decided to keep them outside the scope of this review. While these features can be important for overall ease of use, our intention with this comparison is to focus on the quality of the images and sound as they apply to streaming.

展品A:视频

To test video quality, each camera was used to create a 20-second video with eight separate scenes. Each scene was set up with specific lighting intensities and distances, and different scenes were created to measure motion versus non-motion, 颜色的准确性, 图像分辨率.

All three cameras record in NTSC DV format, which has a frame size of 720x480 pixels. The video was reduced to 640x480 and 320x240 resolutions for the purposes of our tests. Raw still frames taken from the DV file prior to streaming compression were used to arrive at the quantitative results in Figure 1.

	分辨线	视频噪声	视频噪声RR*	图像对比	图像对比度RR*
索尼VX2000	430 (280)	4.3 (3.5)	6	64%	8
佳能GL1	425 (280)	2.7 (2.3)	8	66%	7
佳能Elura 2mc	400 (280)	6.2 (3.9)	4	74%	5

Resolution shown in Figure 1 is "limiting resolution," where adjacent vertical lines merge together. 在我们的测试中, the 索尼VX2000 beat the others by a hair on high resolution (see Figure 3 for a test sample image), but the three cameras produced nearly identical resolutions at 320x240 (resolution values in parentheses).

Video noise is found from a histogram of the pixel values in a small area of the plain white card image (one of the eight scenes). Video noise level shown is the intensity variation as a percentage of the full range. Since pixels are averaged together when reducing resolution, the smaller frame size (represented in parentheses) shows less noise. 在这里, the 佳能GL1 produced the least video noise — by a long shot.

	带宽	噪音底限(dBfs)	(THD + N (dB)	音频质量RR*
索尼VX2000	30Hz - 21kHz	-67(手动-62)	-55(手动-59)	6
佳能GL1	44Hz - 18kHz	-66(-73英尺. on)	-42(-42英寸. on)	4
佳能Elura 2mc	26Hz - 16kHz	-66	-42	4
爱华AM-C80	10Hz - 20kHz	-74	-63
斐济海龟海滩 (PC sound card, line-in)	10Hz - 22kHz	-93	-81

The image contrast test reflects the percentage of the full black-white range, separating the brightest from the darkest square on the color test chart available on the site. A lower contrast number means a more realistic image. A camera with higher contrast will saturate more quickly on bright areas of a scene, reducing the image quality. 在这里, the 索尼VX2000 pulls ahead slightly, with the GL1 on its tail, but leaving the low-cost Elura in the dust.