I've been testing and using the Logitech C920 for a week now. This is really a nice little camera! It takes good, sharp video, and the Logitech Webcam Software (LWS), works fine, though a bit limited in settings.
For those wanting some tech specs, I ran a bunch of tests and analyzed the files with MediaInfo.
LWS provides 4 modes: 360p (640x360 WMV), 480p (864x480 WMV), 720p (1280x720 MP4/AVC), and 1080p (1920x1080 MP4/AVC).
In "Preferences," under the "Quick Capture" tab, it provides 3 audio and 3 video quality settings:
Audio:
Good (16) -- 16kHz at 20kbps (mushy)
Better (32) -- 32kHz at 48kbps (fine for voice)
Best (48) -- 48kHz at 191kbps (DVD quality)
-- These only matter at 360p and 480p.
-- In the higher modes, the audio (AAC) is always 48kHz at 99kbps (vbr), no matter where you set the audio quality setting (bug?).
kbps and frame rates : ( 360p WMV / 480p WMV / 720p MP4-AVC / 1080p MP4-AVC )
Standard (small file): 549 at 15 / 1155 at 15 / 2000 at 30 / 3000 at 30
High Q (medium file): 943 at 15 / 2848 at 15 / 3000 at 30 / 4000 at 30
Lossless (large file): 1723 at 15 / 3848 at 15 / 4000 at 30 / 6000 at 30
-- In 360 and 480, the video bit rate will vary quite a bit depending on the amount of motion in the video. Frame rate is constant at 15.
-- In 720 and 1080, the bit rate is constant, and the frame rate is constant at 30, tho MediaInfo sometimes shows it as variable.
So you can see the highest quality mode is 1080p at 6000kbps at 30fps, which is probably what you wanna use if you're gonna pull it into an editor, and then spit out the results at say, 2000, which makes a good quality video at a reasonable file size for uploading to YT, etc.
I don't know what they mean by "lossless," because what the software calls "lossless" is a mere 4-6 Mbps, highly compressed by the camera. But it's more than good enough.
For the two AVC modes, the camera is putting out profile Baseline @ L4.0, no CABAC, 1 Reference Frame, CBR, and CFR. The color model is YUV 4:2:0, 8-bits, Progressive, as expected. This profile is widely compatible with many consumer HD video devices and software players.
If you're gonna simply downsample the bitrate with Handbrake, you should make a profile that matches what the hardware in the camera puts out. Make your Handbrake (v0.9.6+) profile like this: -f mp4 -O --crop 0:0:0:0 --strict-anamorphic -e x264 -b 1500 --vfr -a 1 -E copy:aac -B 0 -6 auto -R Auto -D 0 --gain=0 --audio-copy-mask none -x bframes=0:8x8dct=0:cabac=0:weightp=0:ref=4:psy-rd=1.00,0.15 --verbose=1 (where -b = bitrate and -E copy:aac = audio pass-through). Note that I set RefFrames to 4, as it falls back to L3.1 if the ref is left at 1.
What about other video resolutions and modes? Running other capture software, like BB Flashback or AVS Video Recorder, you can pick all resolutions from 160x90 to 2304x1536 (at 2 fps) and the C920 will switch to any of them -- so, yes, it will do all the 4:3 modes like 640x480, but not with LWS. There's no reason they couldn't put some common 4:3 modes in it, because the camera will do'em all, and wide-screen isn't always desirable.
Does the camera put out raw video in the non-AVC modes, like a regular webcam? In LWS my processor (dual 3.06GHz) runs about 25% capturing 1080p, but about 45% capturing 480p. In other capture software, capturing 1080p in mjpeg or mpeg2/xvid maxes out the processor and stutters badly. So it would appear that the camera's hardware compression only kicks in with 720p and 1080p AVC, and a good thing it does! My computer (and its USB2) won't handle raw 1080p/30 video.
Snapshots, using LWS (all JPG, Q unknown and not settable):
Low: 1920x1080 (2MP, 472kB), a bit blurry in the details
Med: 2304x1536 (3MP, 649kB), the native resolution of the image sensor
Lrg: 3280x1845 (6MP, 1047kB), interpolated
Max: 5168x2907 (15MP, 1984kB), interpolated
-- I can see no detail difference in medium, large, and max, so interpolation is useless (as expected).
-- I took the sharpest snapshot at 2304x1536 (its native res.) in another capture program that will save a BMP (uncompressed). Indeed, I took that and up-scaled it to 15MP in IrfanView, then saved it as 80% jpeg, and it's half the file size and better quality than what LWSs "Max" setting provided. IrfanView took the 45 meg BMP down to a 1 meg JPG (at 80% Q) and I can't see any difference in details.
Now for the little complaints: None for the camera, but the LWS software could use some 4:3 resolutions and finer-grained controls, like setting the bit-rate of the audio and tweaking some AVC profile settings, more video containers like AVI and MOV, and an uncompressed (BMP) option for snapshots.
RightLight: Doesn't seem to do anything. Either the Exposure and Gain are in Auto or not, and you have to uncheck RightLight to uncheck Auto. In auto, the exposure slider usually stays at 9 (of 14) clicks, and the gain varies. Fast motion is nice and smooth, though blurry. With ample lighting, you can improve the video a little by going to manual and putting the exposure at about 5 clicks and then up the gain for a normal picture, and there will be much less motion blur, just like setting a faster exposure on any camera.
I found one little bug in LWS: When you put the Gain in manual, it will slowly creep down, about 1% per second. It's annoying.
Auto White Balance: Makes you look cold and dead. Set your lights, hold a white card about a foot in front of it, then turn off AWB, and you'll look about right. Also, reducing the Color Intensity a bit makes faces look more natural. YMMV, so don't be afraid to put it all in manual and set it just right for your lighting. And remember, no "auto" stuff will completely fix every lighting situation. I'm using a 45-watt, 5500K, CRI-91 full-spectrum Alzo CFL, and still need manual tweaking.
RightSound: A simple auto-volume that cuts the volume to about half if you get too loud. Seems to take about 1-2 seconds to respond. LWS has no VU bars or mic test, so you have to run something else to see what it's doing. There is a mic level slider in Preferences and I found it to be too loud at the default mid-point; putting it at about 35% made the audio better. There are no audio equalization settings, and it's just a bit "boomy" for my ears. A simple bass and treble filter would be nice.
Stereo: If you're right in front of the camera, it sounds mono, but if you move around, you sure can hear the difference! But the software should have a mono setting, for those times when it's pointed at something besides your face (like, your hobby on the table), and you're talking beside the camera.
Autofocus: The range is from about 1.4 to 14 inches, and everything beyond that is infinity. To get it to macro-focus, you have to move in slowly, and the object needs some detail, or it just loses it and goes back to infinity. Better turning it off and setting manually for the task at hand. But if you're talking within the 14 inches, the AF tracks pretty well and is reasonably fast.
Face following: Because it's just moving the image around on the sensor, you have to be zoomed in some for it to work, and it only works in 360 and 480 modes. At most, it only "follows" for a few degrees of angle.
Didn't try any of the "Effects" -- not my cup of tea. You cannot use them at 720 and 1080, only 360 and 480. Didn't try video phone or chat, so can't comment on that.
Overall, I'm very impressed with the C920, and happy I made the purchase. And glad I didn't get the C910, because my computer won't handle raw 1080p.
--kv5r
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