I used the windy day as an excuse to go outside and play with my new Zeiss 50mm 1.4 lens on my 600D/T3i. I set out to test out the Magic Lantern v2.3 bit rate control. As shown in the settings below, I set the ISO to 100 and a 1/78 shutter. I would normally have it at ISO 160 and 1/48 shutter, but I was trying to get the aperature around f7 to f9, so I used the ISO and shutter speed to reduce the exposure. The only two CBR rates I tested and show in this video are 2.4x and 1.0x. Actually, I tried higher than 2.4x, but the the camera would stop recording almost immediately. In previous experimenting, I had found 2.4x to be fairly reliable when audio is off.

The video shows a 100% zoom and then a 500% zoom of the two shots. Since these were trees blowing in the wind, I had no real control over getting the exact same conditions. But, I think they are similar enough to be able to see the effect of the 2.4x CBR on the quality, especially on the zoomed images.

I encoded this ~2 minute video at a reasonable bit rate (VBR Two-Pass, average 25 Mb/s) to try to preserve as closely as possible what is there. But, it still might be too low to see the differences (since it is far lower than highest raw bit rate). The only thing I did in post is add the captions, zoom, and adjust brightness to video levels. I have allowed downloading, which I recommend, as don't think the true differences survive Vimeo's scaling and encoding. I think the 500% zoom shows the differences in the downloaded file, but possibly not on the Vimeo version.

You might also want to download a much shorter 10 second clip (5 seconds at each bit rate) that I encoded at 115 Mb/s average. You can find that video file here: vimeo.com/48694502

I used VLC player to observe the max data rate during playback of each raw clip.

CBR 1.0x
Avg data rate: 46 Mb/s
Max data rate: 49 Mb/s

CBR 2.4x
Avg data rate: 105 Mb/s
Max data rate: 115 Mb/s

600D/T3i settings via Magic Lantern:
Audio: Off
Video: 1920x1080 24p
Shutter Speed: 1/78
ISO: 100
Picture Style: Marvel 3.4 (0,-4,-2,0)
SD Card: 32 GB Sandisk Extreme 45 MB/s

As always, comments are welcome.

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