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After my last slow motion tests with my Sony HVR-V1P, CDMo reader FANF gave me some quick tips on how to run a resolution test.

Now here is a little protocol for definition testing: Get his first: http://www.graphics.cornell.edu/~westin/misc/ISO_12233-reschart.pdf
Print it 350 dpi min, 600 recommended.

Place it in a well lit spot, in the sun for example, fixed to the wall. Use a spirit level. Place your camera with the optical axis perpendicular to the plane of the testchart (measure hight, use spirit level).
You should not see the white triangles on the underscanned image. No white triangle pointing into the image, the black triangles should ideally be pointing to the perfect edge of the screen.

To test the resolution/definition on the full breadth of the lens, do a test at wide angle, mid, and full tele, placing camera/testchart at the right distance for the scale to be right.
It would be equally important to test each focal at iris values 1.6, 2.8, 4, 5.6, 8, 11 to have a good idea of how definition rises and falls when you stop down.
To do this, use the “aperture prioriy” or “Av” program mode on your camera for correct exposure.

The definition of your camera, horizontal & vertical being distinct, is read by following the lines along the higher numbers ; the number where you cannot distinguish them from one another is your definition, in n x 100 lines. (Make sure you zoom into digitalised footage to measure the image, and not your screen !)

Now I have to admit that I didn’t quite go through with all of the different angles and apertures, and I’m not entirely certain that the resolution chart was printed to the correct size, but it doesn’t matter, as the difference between different shooting modes is obvious, even without meticulous shooting and calibration.

The images created by this process are reasonably large (1920×1080 to be precise), so I’m going to offer some small crops to discuss, and then offer up the full size images for download and examination at the end of the piece, if the mood takes you.

slowmores-01-uncompressed

First up, a couple of 1:1 crops taken from the uncompressed HDMI output of the camera. This is with no HDV compression, so apart from JPG compression for the web these are the pixels as seen by the sensor. Obviously the lighting is a little low, but you can see that the resolution goes down to around 800 lines before it starts getting difficult to distinguish. All of the numbers and markings are easy to distinguish, and there aren’t any hugely obvious compression artifacts.

slowmores-01-3sec

Now to a 3-second burst from the Smooth Slow Record function. Once again this is taken from HDMI (an aside, Smooth Slow Record outputs through HDMI as well as to tape, so you can record it direct to disk with an input card such as the Blackmagic Decklink), so this is just the camera’s CMOS resolution squashing to get those extra FPS. It’s quite a marked difference, Numbers are almost illegible, and it looks like there’s around 200 lines of resolution, or 1/4 the uncompressed version. Makes sense really, as we’re getting 4 times as many frames per second, but it’s very interesting to see just how much details is lost. This should still give around 480×270, which is definitely fine for web video (as we’ve seen in previous slow-mo posts) but not really enough for SD. I think if you chose your subject well and spent some time in post-production you could take this to an SD project, but HD is out of the question without some serious effecting.

So obviously this CMOS buffering takes away some resolution. Next I tested the 6 and 12 second bursts, to see if any further resolution was lost by the longer shooting time.

slowmores-01-6sec

slowmores-01-12sec

As you can see, the difference is marked. Although I feel these images probably initially contained a similar pixel count from the sensor as the 3 second burst, they seem to have undergone drastic compression to fit all of those extra frames in the buffer before they’re written out to tape. These compressed frames are then upsized to 1440×1080 before they’re written to tape, which is why those compression artifacts are so prominent.

To me this isn’t really saying much we didn’t already suspect. Getting 4 times more frames per second results in losing 3/4 of the pixels per frame. It definitely doesn’t invalidate the Smooth Slow Record mode, but it does give us some parameters in which we can use it, and it’s nice to get some reasonably qualitative data on what happens in these modes.

1:1 full crop resolution charts (JPEG, quality 12): Uncompressed [1,222KB], 3 second [931KB], 6 second [832KB], 12 second [800KB].

  • DaNni

    I don't quite understand how the high fps hdmi capture works… are you capturing the full high-fps sequence in real time or after recording it, from the buffer or from tape? Is it embedded somehow into the 1080/60i stream?
    Please elaborate for those who don't own this camera.

    Thanks.

  • http://www.jaymis.com Jaymis

    Good question DaNni.

    The HDMI out is different from Firewire in that it's just a feed of what the sensor (or screen, I suppose) is seeing.

    With normal speed shooting this means you're getting a full 1920×1080 signal, without any MPEG2 compression that HDV entails. HDV is also written to tape at 1440×1080 with a 1.33 aspect ratio on the pixels, so it's considerably lossy compared to the detail that the sensor contains.

    With High Speed shooting in the camera, what happens is that the camera buffers 3, 6 or 12 seconds of action at 200FPS (or 240FPS for NTSC units), and then writes the buffered frames out to tape in 25 frames per second "real time". So you'll record 3 seconds of action, and then it will spend 12 seconds writing that to tape, and you see a preview of what's being written out on the preview screen.

    Obviously this has to then be captured from tape back to computer. HDMI bypasses this, as it displays the "realtime preview" as it's being written to tape, and I can then capture that to hard drive and not bother taking footage from the tape. It doesn't give any extra resolution, but it's just slightly more convenient.

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  • http://mxmai.com/blog mxxx

    i've been using an FX7 for the last week or so, which is the little brother of the V1 and has a 6 second smooth slow burst on it.

    i'm torn, because on the one hand it's almost really good, but at the same time the loss in resolution means it's really hard to find a use for the footage. shame.

  • http://wattsunique.com/blog/ Nick Watts

    Dear people that know a lot more about this than I do,
    If you go to the above blog and check out my last couple of postings you will find some slow motion footage I would like to upgrade.
    I am wondering if this Sony slow/smooth record feature would allow me to get better results that seen in my blog. I had to take a movie of my computer screen as it was playing on slow to get that footage……yuk!… Please advise. Thank you, Nick Watts.

  • pakmenu

    Sony is very smart in saying there is no CAMCORDER that can take higher framerate slowmotion… as the Casio Exilim EX-F1, an extraordinary camera that can take 6 Mpixel resolution pics at 60fps for one second and Hi-Speed Movies @ 512 × 384 (300 fps), 432 × 192 (600 fps), 336 × 96 (1200 fps! needs lots of light)

    This is so much faster then all of the others that though it as released in march 2008 it has seen no compettition yet and in fact the new slowmo and continously record and have footage from BEFORE you pressed the trigger functions of 2009 are thanks to casio's innovations.

    this speed is achieved thanks to PARRALEL (instead of line per line) extracting of data from the Cmos chip, also why it also has no Rolling shutter effect!

    The Sanyo Xancti new 1080p60 (progressive!) HD series also can take 300fps slowmotion movies, but probably less quality then the Casio (needs research)