HV20 gain

Barry, if the you do the test at full wide zoom, it looks like the aperture stays slightly more open than if you zoom in 100% on a bright source. In other words, with the 50/50 zebras at 70% when locking exposure, -11 does not seem to completely close the aperture. Looking at an angle of about 45 degrees (using an overhead CF bulb) you can see the reflected light in the aperture opening change colour suddenly ..and it does it twice. I observed the exact same type of ND filter (2 stage that slides in) from the GS400 looking through the lens. An led cap would work perfectly with what I tried in TV mode. Instead of using zebras at 70% and locking exposure when 30-50% of the frame is in zebras, an LED array in the cap could be used combined with metadata viewing (on the other HDV cam) to absolutely set the baseline. I'd buy that cap!

Btw, the only way I could visuallize the aperture and ND filters was with the cam fully zoomed out. That brings the rear element forward so you can visualize it.

On the iris side of things, I haven't tested the HV20 at all for diffraction due to aperture blades etc, but I suspect like the other cams similar to it, f4 would give the sharpest image. I have observed some vignetting introduced from the video cam's aperture before when using an adapter, so some testing with your selection of 35mm lenses would be a good idea if you plan on stopping the camera down. The stinker with these consumer cams is you can't lock in f4 and dial in an internal ND...meaning if you're into the internal ND's you're also using the smallest (not ideal for image quality) aperture.
 
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Didn't try it wide-angle, I'll have to try it that way.

For diffraction, it really tries to not go below f/8; you have to really, really push it before it'll go past f/8. Normally it'll start changing the shutter before it changes the aperture deeper than f/8, but you can make it happen, I've seen something odd like f/19 before but it was when I was tracking some seagulls and they went in front of the sun.
 
I can only suggest we shot color charts and faces at various light intensity.
Verbalize all dial settings .

And a set of pan shots past dark and light objects before going on a real shot ...
Then throw it up on a monitor .There is always someway to get comfortable with your equipment ..test ..test ..test
until you know this little beast ..you need a good monitor .
 
Helpful and real useful valuable info for the upcoming HV20 users. 5 stars (EDIT -- done) thread.
 
Is there a way the important sections about how to properly control the hv20 because of it's limited manual features can be put in a different thread and stickied? I'm not 100% sure if you guys found a way around the expose thing or not and I'm sure we'd all like to know the conclusions without reading 9 pages.
 
Shutter speed and Variable frame rate

Shutter speed and Variable frame rate

Hi,
I have two questions that I'm wondering if anyone knows.

1.) Regarding shutter speed, can the HV20 handle higher shutter speed like 1/250 or 1/500 in 25P/24P and Cinemode?

2.) Is it possible to do variable frame recording. Like recording 1 frame per minute?

Thanks
 
rob, yes it can handle higher shutter speeds in 24p, I suppose 25p for PAL. You do this by setting the shutter speed in TV mode.

Cinemode, to me, appears to always have a locked 1/24 shutter, just my observations with my eyes.


1 frame per minute (timelapse) is not possible with the HV20 unless you capture to a laptop live via something like DV Rack, HD edition.

You could get 60 frames (almost three seconds of video) if you shoot a whole tape and speed it up in post. Lots of trouble just for 3 seconds though.
 
Cine mode attempts to keep the shutter locked on 1/48 as much as it can. It can go slower, under low light circumstances, but in adequate light it will stick to 1/48.
 
So you feel it will not want to go faster than 1/48 but will go slower if there is not enough light? I have found it going to 1/24 in s scenario that looked pretty good to me as far as available light is concerned.

Barry_Green said:
Cine mode attempts to keep the shutter locked on 1/48 as much as it can. It can go slower, under low light circumstances, but in adequate light it will stick to 1/48.
Click to expand...
 
It can go faster or slower depending on what it thinks the prevailing conditions are. I've found that I can lock it and keep it at 1/48 throughout the range of -11 to +5, but once you get to +6 it starts changing the shutter. Whether it "looked good to you" isn't the issue, it's what the camera needs that's the issue, and CMOS cameras and especially tiny-pixel CMOS cameras are not good at all at gathering light. I should do some comparisons against some of the other cameras to see what it's like; thing is, you don't really KNOW what it's doing, because it doesn't tell you. It might be running with 27dB of gain for all you know...

You can find out your shutter speed and aperture after-the-fact by turning on the Data Code in the display and playing your footage back. It won't tell you gain though.
 
I understand Barry. I just thought you had determined 100% that the cinemode preset would not allow a higher shutter speed than 1/48.



Barry_Green said:
It can go faster or slower depending on what it thinks the prevailing conditions are. I've found that I can lock it and keep it at 1/48 throughout the range of -11 to +5, but once you get to +6 it starts changing the shutter. Whether it "looked good to you" isn't the issue, it's what the camera needs that's the issue, and CMOS cameras and especially tiny-pixel CMOS cameras are not good at all at gathering light. I should do some comparisons against some of the other cameras to see what it's like; thing is, you don't really KNOW what it's doing, because it doesn't tell you. It might be running with 27dB of gain for all you know...

You can find out your shutter speed and aperture after-the-fact by turning on the Data Code in the display and playing your footage back. It won't tell you gain though.
Click to expand...
 
No, I determined the opposite -- cine mode can definitely step outside of 1/48. But it really tries to stay at 1/48.

Only way to guarantee 1/48 is to use shutter-priority mode.
 
Did some shooting with the Brevis and HV20 over the weekend. Playing the tapes back, (view data) I was able to lock in f 4.2 and f 5.6 using the TV mode/exposure method posted a page or two back. Shutter was locked a 1/48 and I used a 50mm lens at f4 for most of it. Had .9ND and CP 4x4 filter up front.

Our HV20 has a terribly non lens-centric image. It's skewed way to the right...and the first time I've seen this on a small cam. When framing the Brevis imaging elelment it's not a huge deal, but still strange to see in a small cam. It's not unusual on the HD100s.
 
I received my HV20 just before I went on Vacation in March, and noticed all the same things you folks are describing. However, I purchased my camera specifically for it's size and holiday travel- not filmmaking. So these issues don't concern me. However, working in the field that I do- it's a curiosity.

However, getting this figured out should not be too difficult. Here's my theoretical approach, create your standard HV20 settings (Shutter Priority, Cine, whatever)- use the HDMI output and an HDMI to HDSDI converter and Leader 5700. Shoot a Chroma DuMonde, experiment by adding FC until you get the optimal "neutral" exposure point. Try both 3200 and 5600 and compare if they match.

Here's the trick- find a color chart that has a wedge that'll give you either 70 or 100% zebras at that optimal level, you may have to make something and may take some experimenting. In the field rate your light meter at that point to determine chart light FC (or exposure at your choice of ASA) and from that point you should be able to set your baseline neutral with a chart, light (probably ng gels for daylight), and zebras when shooting.

Should be a simple way to maintain that starting neutral point for maximum exposure control without gain or shutter involvement. You should be then able to confirm results with the FX1 or similar camera.

I'm totally slammed through NAB, but if no one else has done it by the end of April maybe I'll spend an hour or so and figure it out.

I.

Will this jet lag never end!
 
Barry_Green said:
Also, as for variable ND filters -- the Singh Ray variable ND is $400. Er, that's a tad expensive for a $925 camcorder. But apparently the Singh Ray Vari-ND is merely a circular polarizer with a linear polarizer in front of it. So you could probably grab a circ-pol and a linear-pol off ebay cheaply, stick 'em together, and come up with a similar solution.
Click to expand...

I agree I'd bet it's just two polas. I think Tiffen sold the same thing many years ago. It might be possible to find one on ebay for less than half the money. You'd just need to add your own marks. I seem to remember even owning the Tiffen version but sold it with my CP-16R.
 
Illya Friedman said:
Barry_Green said:
Also, as for variable ND filters -- the Singh Ray variable ND is $400. Er, that's a tad expensive for a $925 camcorder. But apparently the Singh Ray Vari-ND is merely a circular polarizer with a linear polarizer in front of it. So you could probably grab a circ-pol and a linear-pol off ebay cheaply, stick 'em together, and come up with a similar solution.
Click to expand...
I agree I'd bet it's just two polas. I think Tiffen sold the same thing many years ago. It might be possible to find one on ebay for less than half the money. You'd just need to add your own marks. I seem to remember even owning the Tiffen version but sold it with my CP-16R.
Click to expand...
BTW, any suggestion on useful links?
 
What I am interested in is a good way to get as much exposure range as possible at 0dB after locking the exposure in Tv mode... like the cellphone trick that Barry tried. Any tips on that would make a great sticky.
 
If you set zebras at 70% and lock exposure with about 30% of the frame showing them, you'll get a range of +-11 with 0 corresponding to ~f4

I've finally worked out a reasonable work flow for pulldown removal (PC based) too.
 
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