General Weather - all topics not current severe weather.

[Michael Bath]

Hi all,

I'm slowly building up the knowledge to get the best out of my new Canon HV20 high definition video camera, particularly when it comes to lightning footage and grabbing frames. I guess it is a fairly obscure subject that we enjoy and finding information about the best recording modes has not been easy.

Firstly it is amazing how big the image size is compared to standard DV - we are talking double the resolution horizontally and vertically - plus the step up to widescreen gives even more. I've spent a bit of time on the HV20 forums as well as experimenting with recording of four lightning active storms.

Initially I had the camera set to HDV 1080i25(50i) which is the default high definition setting. 50 interlaced frames per second. Video stills of some lightning gave mixed results with 'rolling shutter' apparent. The footage was taken with auto settings.



full image sequence



full image sequence


It then dawned on me I should be using the HDV 1080p25 recording mode which is the full progressive 25 frames per second. Apart from changing to that, recording was still in auto. The results were stunning on my next storm chase.










full image sequences


Still using those same settings, but this next storm was in darker conditions. I am still yet to be sure but I believe the camera automatically adjusted the shutter speed below 1/50th second. It is normally 1/50th in decent lighting conditions. I have since learnt it is important to have the shutter speed double the recording mode. So use 1/50 (or higher) for 25p, use 1/100 (or higher) for 50i. The results with this darker scene are below and you can see the rolling shutter problem has resurfaced - and some overexposing of the lightning has occurred too.





full image sequences

Some may be asking why bother with stills and this testing anyway? When they are this good it is rather worthwhile to get stills and they can compliment a chase report nicely when it is impossible to get photos. Also that rolling shutter effect is visible on video playback on a PC - though may not be on a TV. So I'd like to get it right.


The final bit of information which I have learnt today is that Premiere was not putting out stills as good as they could be though I probably have not worked out the best method in that program. It's also a pain in the butt to export frames one by one. Premiere was making them 1440 x 800 pixels with that black bar top and bottom. Using another program to extract an image sequence from a small clip resulted in the full sized 1920 x 1080 pixels !!   Example below.



This was a staccato with no lightning showing up in frames either side.

I'll add more to this thread if I find out more.

Michael

[Shaun Galman]

Hi Michael,
This information is tops! I have been looking into the purchase of a great DV camera for some time now but it is a risk to outlay a small fortune for a camera to use just for this purpose (storm recording) only to find out it has not lived up to it's expectations? These few first images are stunning to say the least, not to mention, they would print well as a bonus! Daylight storms are all well and good to photograph but if you cant manage to catch that one great looking bolt with a stills camera (possibly striking something in the distance) it can be rather frustrating.
This camera is the answer!
 
I think this is indeed valuable learning and I cant thankyou enough for sharing your findings Michael. You've done the hard-yards for us and learnt from a relative few minor mistakes to give us all a great head start :) I still cant get over the amazing images, the contrast and colours are just as good, if not better, than most small point&click digital cameras! I could imagine how good the running video would look on my viera plasma lol! ;)

I will definitely add this camera to the wish list for the immediate future as I'm sure most of us weather enthusiasts will once they see your results, particularly at the next ASWA meeting!
Cheers,
Shauno   

[Mike]

My thoughts echoed by Shauno.  Video capture is probably the next tool one gets after their camera increasingly due to wanting to watch motion, rotation, lightning etc.  There's so many brands around at all different prices that anyone who is just beginning to use video really does not have a lot to go by unless someone has used a particular brand and can recommend it.

You've been out in the field testing this Michael so thanks for imparting your findings with us.  The stills are of a high quality and it's rewarding to see it all played back to oneself after the chase!  The added bonus is that because of the HD quality you can make single shot photos - always nice during the daytime stuff - just imagine what the nighttime shots will come out like if they are this good - albeit the die-hard photogs will say it's cheating!!!  Not so in my opinion - you have to get the best pictures by whatever means you have available - it's hard enough with a SLR camera, with this little baby no one will tell the difference anyway and you've captured what you wanted.

Cost for this little bit ot technology?

Mike

[Michael Bath]

Amazingly well priced. Retail shops vary from 1600 to 1900 and online prices 1400 to 1700 so not that bad, though I realise non-high def video cameras are only a few hundred bucks these days.

The HV20 uses standard mini DV tapes which is great too as they are not expensive. There are HDV cameras with hard drive storage, but you have to store what you transfer when the hard drive gets full. Tapes are still the cheapest option and give you the best quality too. No doubt it will be quite different when it comes to storage in a few years.

[Michael Bath]

I am still yet to be sure but I believe the camera automatically adjusted the shutter speed below 1/50th second.

Actually - discard some of what I said before. I found out that you can display the F-stop and shutter speed on play back.

It revealed that the shutter remained constant at 1/50th for that footage on 9th Dec (the group of 6 images above). What did change was the aperture - mid way through frames I gather - this is the 'rolling shutter' effect.

Here's some more examples. Playback showed the F-stop changed from F1.8 at the start to F2.0 by the end of this lightning. Given we are talking 25 frames per second, some of those aperture adjustments are going to be too fast to show on the LCD, so there could be some quite major changes happening within a fraction of a second. It's a pity those settings are not transferred during video capture as then I could be checking the settings frame by frame. Note the first few frames have changed exposure half way through before it settles down when the lightning is far less bright during the return strokes. I assume there must have been some very bright overhead lightning occurred before the CG occurs.










With this next sequence the shutter speed and aperture remained constant at 1/50 and F2.0 according to the LCD. It would appear the camera tried to make a rapid exposure adjustment when the initial discharge of lightning occurred but it was too late and over-exposed that frame.








This next one had the shutter speed at 1/25 and the aperture at F1.8 prior to the lightning occurring. The LCD showed the shutter go up to 1/50, then the aperture went up to F2.0 by the time the lightning had finished. The rolling shutter effect due to exposure changes is again quite obvious on the first frame.






For those who want to see all the frames, the full sequences of all three lightning bolts referred to above are available here


Conclusions at this point

I'm still assuming some things but it would appear that:

- darker scenes where the camera has the aperture pretty much fully open is going to result in some over-exposed frames when close lightning occurs - yes, we should all know that already :)

- F5.6 and 1/50 was the setting for the nice bolts in my first post (with the pine tree in it), so F5.6 is quite a good balance for not getting over-exposed branched lightning. The camera on auto did not sense the need to adjust the exposure (I assume)

- the obvious thing to do is use manual settings when you are setting out to record lightning. 1/50 shutter speed and as high an F-stop as the scene will allow when the lightning is going to be close. I will test this on my next outing to see whether the full manual control will eliminate the rolling shutter effect caused by rapid exposure adjustments by the camera when set to auto.

[Dave Nelson]

Hey Michael,
                    I wonder if your camera is CMOS or CCD ?
to quote another storm chaser Dan Robinson, from Stormtrack forum ....

  CCDs are better than CMOS for chasing, as CMOS chips tend to have worse low-light performance. Many CMOS chip cameras have rolling shutter problems which make them useless for lightning, although I've seen footage from a few newer CMOS cameras that do OK with it. CMOS chips do better in well-lit situations than most CCDs.

end quote
and if your wanting to go HD video ...

quote....

AVCHD is supposed to be a slightly better compression codec than HDV, but at the expense of needing more processing power to handle it on the computer end. AVCHD is not yet supported in many editing software packages.
end quote


that rolling shutter effect is really annoying, the way it chops up the pic,  seen that on my old now
dead JVC camera

Dave N

[Michael Bath]

Dave - yes - CMOS.

Yet to do anymore testing due to the lack of storms - hopefully soon.
MB

[dann weatherhead]

Thanks for this exhaustive catalog of info Michael. I own the Sony HCR HC1 which is a first gen HDV camera. The camera has been great over the past few years, save lightning. I have had major issues with capturing good lightning. THe HV20 looks like the best camera at its level on the market. A friend of mine shoots for the ABC and says that the HV20 has a better picture than many of their 15000 Sony Betacam's. From these examples it looks like their is some combination that alleviates the rolling shutter effect. We tried stopping the shutter speed down to 1/25. While this was okay - any motion in the picture is blurred and the close bolts still resulted in that crappy effect.

I look forward to more on this.

[Michael Bath]

While I still have not had any more storms to test again, I did read some info on the HV20 forum that may be useful for the next opportunity.

There were recommendations to have the shutter speed set to twice the frame rate - ie. shutter priority set to 1/50. Then use the manual exposure control and set it to -1 (or whatever) so that the camera will not adjust the aperture during filming.  You just have to remember to switch that manual shutter control off once you change scenes.

[Shaun Galman]

Hi guys,

Michael: Here's something that may not seem as important as capturing those great lightning stills but, how do you find the sound reproduction with the HV20? Just wondering as the purchase of an awesome DV camera such as this would surely get a fair bit of use in the off season for other things, I'm a musician so it may serve me very well if the sound quality is good. Also, I'd love to make a decent and accurately realistic opal mining video (as opposed to the inaccurate ones that have been shown on TV over the years!) at some stage. Not too sure how you'd get a feel for this, maybe by using familiar voices or recognizable background noise in a recording for comparison?

Regards and take care.
Shauno

[Michael Bath]

Hi Shauno - the sound recording appears better than my previous JVC and has less noise from wind blowing on the mic. All people on the HV20 forum suggest you get an external mic for serious sound recording though - that probably goes for any video camera.

[Jeff.H.]

Hey MB long time no see! I purchased a HV20 in November and I too have had mixed results. Night time seems to be most difficult with CGs ect. I'll read some more into this thread then get some images up from chases so far... I have no doubt with time and experience with this champion camera we will get what we want:P. PS: Oh my god at HD file size- something like 11gig/hr of recording!

* Edit* I have found manual settings for CGs and lit structure work at night work best some examples>>>



Cheers Jeff.H.

[Mike]

Welcome Jeff and your first post!  Great capture of the layering with the lightning illuminating them, wow factor.  Have not gotten into the HD videocam thing as yet, it's taken me long enough to get used to my SLR!  It's one thing one must invest in if one wants to view the 'show' as it were when filming storms.  Always nice to watch the storm go through its motions in time lapse - not forgetthing any flangs!

Mike

[wthrman]

MB, my thanks also for this information. It just happens that I too have been thinking of upgrading my present (and now outmoded) Canon MVX330i. I have never been happy with the still shots from it; there are always artifacts I can't get rid of, even with processing. I wondered whether this was due to it being a MiniDV. Those tapes must surely deteriorate with time especially in humid climates? I would be transferring the movies onto DVD anyway but I like to reuse the tapes.

Does anyone have any views on which is better (ie tapes or hard disk) and if so, why?

[Michael Bath]

If you plan to archive your footage reasonably quickly to DVD then a hard drive camera may be a better option. Tapes are still the most reliable option for archiving footage long term. I don't re-use any tapes. The HD camera can use standard mini DV tapes so you're looking at about $5 an hour.