Tuesday, December 22, 2009

Flicker test

The HD2000 is purely a NTSC/USA region camcorder since it records in 30fps and 60fps as opposed to those meant for the PAL/European market that records in 25fps or 50fps. But in this age of HD, the question of PAL vs NTSC doesn't really arise during playback on HDTV and I found that I can even playback my videos on my old PAL TV without any problem once I make the correct selection in the playback option.

However, there is some concern that there will be flickering when filming under fluorescent light at certain shutter speed since the mains frequency in PAL land is 50hz against 60hz in NTSC area. Actually I do not notice any flickering in my videos, maybe because most lighting now uses the energy saving bulb or the shutter speeds used by the HD2000 during filming do not result in any flicker or only slightly.

Anyway, at the request of one of my readers, Sergei, I made some short clips using the various shutter speeds that could be set manually. The shutter speeds that can be set manually are the following:

4s, 2s, 1s, 1/2s, 1/4s, 1/8s, 1/15s, 1/30s, 1/60s, 1/100s, 1/125s, 1/250s, 1/500s and 1/1000s.

However, according to the user manual, the lowest speed that would be used in the normal video mode is 1/30s and 1/15s in the high sensitivity (or lamp) mode. The highest speed possible is an astonishing 1/10,000s and I suppose this is seldom used in practice, if at all.

So what is the result of my test? You can see the result in the video below. This is a combined video of 7 clips of about 6-7 seconds each using increasing shutter speeds of 1/30, 1/60, 1/100, 1/125, 1/250, 1/500 and 1/1000 in this order. These were all shot using resolution of 1920x1080, 30fps (30p) and uploaded to Youtube as is without any rendering.

It shows that there is flicker, especially at the higher shutter speeds. There is slight flickering at 1/30 (very close to the light) and also at 1/60. At 1/100, there seems to be no flicker but the flicker starts again at 1/125 and gets more pronounced as the shutter speed increases. The results looks similar using the higher resolutions of 1920x1080, 60 fields/s(60i) and 1920x1080, 60fps (60p) though the flicker is now faster and the best shutter speed to use appears to be 1/100s in all the resolutions.

In practice, I don't see much flicker using the auto mode since I suppose the shutter speed used is 1/125 or lower and we don't normally shoot directly at the lights. Further more, fluorescent lights are now replaced more and more by energy saving lights so there are less chance of flickers while filming. If it is necessary to avoid or at least to reduce flicker, then set a shutter speed of 1/100s manually.

Below is a composite video of clips shot during my visit yesterday to a shopping mall showing the local Christmas spirit. All taken on auto indoor and totally hand-held with no sign of any flickering (probably no fluorescent lights were present). There is some sign of shakiness in the second last clip (dancers on stage) that employed fairly high zooms; otherwise not too bad for hand-held shots. I'll like to wish everybody a Merry Christmas and a Happy New Year with this video.

(Sorry, having problem to upload this second video in Youtube, will post again once OK. I am releasing this post without the video since Sergei seems to be desperate to have the flicker test result.)

Edited on 23 December, morning. This video is now uploaded at Vimeo here. The last song is complete in the original but the last few seconds were truncated during upload so hearts were lost! Merry Christmas, anyway!

Edited on 23 December, evening. At last, the video is uploaded in Youtube. Originally shot in 1920x1080, 30p but rendered to 720x480 for Youtube. This version is about 3 seconds longer than the one in Vimeo and is thus complete and more satisfying. Not sure if the missing seconds is due to Vimeo or to my line during upload. Nevertheless, Merry Christmas. Enjoy!

Ronald Kwok

Sunday, December 6, 2009

Using External Hard Drive - Caution

I wanted to make use of my 640GB Maxtor external hard drive (the Maxtor) that I've been using to store my videos to backup some of my laptop data since there are plenty of unused space available. I thought it would be best to partition off some of this unused space for this purpose so I started Partition Magic and the following message appeared.

"PartitionMagic has detected an error 110 on the partition starting at sector 63 on disc 2.
The length of the partition in the partition table is incorrect. The CHS length is 1250274627, the LBA is 1250263665, and the File System length is 1250263665. PartitionMagic has determined that the length can be changed to the correct value of 1250274627. Would you like PartitionMagic to fix this error?"

Without giving it a second thought, I hit the Yes button and that was a BIG mistake. However when I tried to create a new partition, it came up with another error message (error #2103) that a new partition cannot be created. So I just left it at that.

But horror of horrors, when I later tried to access the Maxtor with my HD2000 the dreaded message "Hard disk unavailable, would you like to format the hard disk?" (or something similar to that effect) appeared. Oh gosh, it seemed I have now lost all my videos! As a last resort, I hook up the Maxtor to my laptop and thank goodness, I could still access all the files there and open them. So the videos were still intact, only problem was that they could not be accessed by the HD2000. The only solution was to transfer all the files in the Maxtor to another hard disk and reformat the Maxtor using the camcorder. This I did and luckily there was only 130GB of data to be transferred.

Thus it appeared that by fixing the "error", Partition Magic has made the Maxtor HDD inaccessible to the HD2000 but luckily it was still accessible through Windows. I didnt' know what that error message mean but it must be something that help identified the Maxtor when the HD2000 is connected. Having transferred all the files to another HDD, the next step was to reformat the Maxtor by the HD2000. After this was done, the Maxtor was again functioning as normal. The final task was to transfer all the files from the temporary HDD back into the Maxtor.

This was quit easily done since I sorted my clips by date whenever I transfer them from the HD2000 to the Maxtor and the videos were store in individual folders named for the date e.g. 20090629 for clips captured on 29 June. All these date folders were stored under an ASSETS folder. First I transfer videos from a SDHC card to the reformatted Maxtor to create the proper setting. Then I just drag and drop each date folder from the back-up HDD into the Assets folder in the Maxtor. (You could just drag and drop the whole Assets folder but since it is rather big, I prefer to do it in small chunks.) This took some time though since there was about 130GB of data to be moved. What a relief when all was done and I found everything working as before.

Lessons to be learned? Well, never tamper with your Xacti Library Hard Disk (the one that is formatted by the HD2000 to store your videos) , especially the partitioning setting. In any case, I could not create a new partition with Partition Magic despite correcting that "error" and probably not with another partitioning programme. Correcting the "error" made the Maxtor invisible to the HD2000. If you want to use the free space, just create a new folder and it could be accessed by Windows but ignored by the HD2000.

Phew, what a narrow escape!

Ronald Kowk