How settings affect shooting times

egproductions

egproductions

Veteran
So one thing a noticed a while ago was how, dependent on your ISO selection, you are able to shoot for longer or take more still photos. When you change your ISO settings from 100 to 6400 it's clear that the amount of photos left on you CF card goes down. I did a test and was able to get about an extra minute of recording time. On a scene that would normally take 12:15 at ISO 160 I was able to record for 13:17 on H1.

I know some people have checked bitrate data on these files and have noticed that you actually get a higher bitrate per frame shooting in 24P than you do with 30P. I wanted to confirm this by doing shooting tests and also see what effect having audio disabled might have on the shooting duration. I did some tests shooting with the camera facing a solid wall with constant light. I let it record until the 4GB fat32 limitation was reached. Each test was shot twice to confirm the duration lengths. Here were my results:

24P, ISO 160, Audio yes, AGC:
14:40

24p, ISO 160, No Audio
15:13

30p, ISO 160, No Audio
12:14

Granted this isn't a sure way of concluding anything, what the results lead me to believe is that when audio is disabled, the extra data is not added to the video bitrate. If the record time was the same or closer between the test with and without audio I would say that you can achieve a lower compression shooting with audio disabled.

The more suprising results are in regards to shooting 30p. I would have thought the recording duration would have been the same between 30P and 24P, this would have meant that more data is dedicated to a single frame but these results lead me to believe that a higher datarate is used for 30P to compensate for the additional frames recorded.

Has anyone else been able to confirm these results?
 
That difference in time is almost exactly consistent with framerate changes, where each frame has the same amount of data (24p is 80% the frames of 30p, and 12:14 is 80% of 15:13).
 
Good point!

If your CF card is having trouble handling the constant datarate of your video, you might get better results by shooting 24P and having audio disabled since 30p and audio seem to just increase the overal datarate, not increase the compression of the file.
 
Very interesting post and food for thought, given a few claims of decreased compression artifacts with the new framerates. Thanks for doing this and sitting there for 45 minutes shooting a blank wall!
 
We don't have our 5DM2 yet, but do I understand correctly that you can keep shooting indefinitely and the camera will just create 4GB files that you can join together for a continuous stream?
 
MitchLewis said:
We don't have our 5DM2 yet, but do I understand correctly that you can keep shooting indefinitely and the camera will just create 4GB files that you can join together for a continuous stream?
Click to expand...

If only....unfortunately, you have to re-initiate the recording.
 
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