Wide Shot Resolution

[Jim Sofranko]

I have been recently shooting with the 3x Canon zoom. Great lense that I love for hand held shooting.

But when I shoot a wide vista I notice that image doesn't appear as sharp as when I shoot a near object with the same lens. Both are in focus but I think it may be that DV (or the Canon system) just doesn't resolve images where the distant objects get so small in frame such as in a wide vista.

Has anyone else noticed this?? Any solutions??

[Boyd Ostroff]

Sounds like a well-know limitation of DV. The heavy compression takes its toll on scenes with a lot of complex detail, like landscapes. Also, as things get smaller there are just not very many pixels available for them. Always a frustation of mine as well.

Last year I did a big project that included photorealistic computer rendered landscape shots as well as real footage. Even though there was no "lens" used in the computer sequences they exhibited this same problem (although the same frames rendered as JPEG's looked much better). If you had a chance to see "28 Days Later" in the theatre on a big screen you would also have noticed that the landscape and cityscape shots looked pretty ragged, although I thought many of the closeups and medium shots looked surprisingly good.

So I guess we just have to wait a little longer for the HDV market to heat up and offer us a few more options :-)

[Bill Pryor]

Cameras with smaller chips will be softer on wide shots, but the lens and back focus adjustment can also contribute to the problem. If the shot is so soft it looks out of focus, then it's probably a back focus issue. Professional cameras have lenses with back focus adjustment; others have to be sent in to a repair facility. However, what you're seeing is most likely just the way it is with smaller chips. On occasion I've done two camera shoots where the second camera is a smaller chip one than the main camera. In those instances I do the wide shots with the bigger camera and closeups with the smaller one, and they usually match fairly well.

[Jim Sofranko]

That's what I figured. I'm working with a director who has never shot on DV and is voicing concern about the wide shots. I don't believe it's a back focus issue either but simply the DV format as suggested.

Has anyone tried different diffusion to help? I know this sounds odd but I'm from the film world and if we have a moire edge problem sometimes a little diffusion helps soften the edges so it is not as apparent.

[Bill Pryor]

You're talking about two different issues. Over enhancement is something else, and it can be turned up too high and get that "edginess" that some people associate with DV because they haven't seen DV shot with fully professional cameras that are properly adjusted. The soft wide shot issue, however, is a function of the lens and camera you're using. On a DSR500/570, the wide shots look pretty good. On a 1/3" chip camera, they don't.

[Jim Sofranko]

So it's an issue of format resolution not a "video in general" issue.

I was hoping that I might get lucky with the diffussion route. When you transfer film to video, edges sometimes buzz or moire depending on the size of the lines in the frame. Shooting a closeup of the old Amex card was a classic example with the small lines on the card. Adding diffusion when shooting often helped. When the Spirit film-to-video transfer machine came along it solved most of those issues.

Thanks.

[Boyd Ostroff]

Bill, you make some excellent points, and thanks for challenging what I believed to be the prevailing "wisdom" on this topic. You got me interested enough to do a few quick experiments, and they would tend to support your statement about optics and chip size being more of a factor than the DV compression itself.

First I took a landscape shot from my Nikon 5700 (a 2/3" 5MP still camera), resized to 720x480, dropped it into FCP, rendered as a DV compressed Quicktime file and finally exported back to a 720x480 still. There actually was very little difference in the results, much to my surprise.

Wanting to quantify this a little better, I did the same thing with a JPEG of the EIA 1956 test chart. There are some relatively subtle differences here if you magnify the image, but not much. I then took a still frame which was exported from DV footage of a high-resolution print of the same chart as filmed with my VX-2000. Wow, the difference there is striking when you enlarge it. You can see for yourself here: http://www.greenmist.com/pdx10/chart/res.jpg. Now I don't claim this to be terribly scientific, but it's enough to convince me. These images are cropped from a small portion of the upper left hand corner of the chart and were originally ~74x128 pixels. I first set auto-contrast on them and then enlarged by 300% using Photoshop bicubic interpolation.

Alas, now I'm depressed! I had always thought the real culprit was the DV codec itself, but now I'm convinced it's the chips in our prosumer cameras...

[Robin Davies-Rollinson]

" I had always thought the real culprit was the DV codec itself, but now I'm convinced it's the chips in our prosumer cameras..."

The DV codec can give far better resolution than we give it credit for.
I recently had some material shot on Digibeta transferred to DV for me to edit into a package. The quality was far far superior than the image obtained from my XM2.
Cheapo "prosumer" cameras really can't cut the ice - whether it's because of the CCD itself or the circuitry, firmware, call it what you will, but DV itself is capable of very good pictures.

Robin.

[Bill Pryor]

All you have to do is look at the differences between a 1/3" chip camera and a 2/3" chip camera, both DV, to see what it's all about. Interestingly enough, to my eye, anyway, there seems to be a bigger difference between a 1/3" chip camera and a 1/2" chipper than there is between the 1/2" and the 2/3" ones.

[Jim Sofranko]

Interesting test.

Does the interlacing acquisition of video have anything to add to this equation? Is it a different method of acquisition in a digital still camera versus digital video?

As to the 1/3" to 1/2" being significantly better than the 1/2" to 2/3" chips, that makes sense to me because there is a great relative difference. In the first comparison you are starting at 1/3" in the second comparison you are starting at 1/2". If there were a 1/4" 3 chipper there would be even a greater difference compared to 1/3".

It also may have to do with a threshold of acceptance for professionial imaging. 1/3" is the lowest threshold IMHO but is becoming much more accepted lately. That doesn't mean that any camera in any format can't make interesting and beautiful pictures. Just that each format has it's pro's and con's as we witness in 1/3" DV wide landscapes images.

[Rob Lohman]

Well, a CCD chip has only so much pixels to see differences. The
wider you go the faster detail changes on a smaller scale
(usually). So I'd say at some point the CCD's just can't see the
extra information anymore.

As for the camera's lower quality compression. I'd say this is
mainly due to processing power available. The DV codec inside
such camera's is probably just of a lower quality than the DV
codecs we use in our PC's, simply due to processing power. I
have no proof for this, but it does make sense. First they need
to combine 3 datachannels into one which is already 30 MB/s.

Then they also need to do this quite resource heavy DCT
compression algorithm and lay it to tape all within a second for
30 frames. That's quite a few things to do. And I'm not even
counting things like white balancing or other effects etc.

So I would not be that surprised if they cut some corners on
implementing the DV codec.

This is all just a guessing on my part, ofcourse...

[Dan Uneken]

I guess that's why some people are looking to capture raw uncompressed video. See this little thread (800 something replies):

http://www.dvinfo.net/conf/showthrea...threadid=20332

[Andre De Clercq]

DV encoding/decoding seldon shows it's shortcommings in terms of resolution..the high resolution parts of the image get a digital value (if above a "visible treshold") just like the "low resolution" area's. So resolution as such doesn't belong to the DV codec. Resolution is limited to 720x480 (576) points for the "ideal" camera. Rather artefacts like blocking, quilting, mousquito noise... are the DV shortcommings. There are differences in DV encoding quality. Once the DCT tranformation has taken place (a mathematical process equal for all cams) come the tricky steps like optimal quantization table choice, motion estimation...and these approaches ( not fully defined in the bluebook) can make the difference. Again,.. not in terms of image resolution

[Dave Croft]

I have just bought a new Panasonic DVC30, and all this talk about chip sizes makes me depressed seen as though mine is just a ¼ incher :(

[Bill Pryor]

The 1/4" chip camera will look good on its own. People have done documentaries using 3-chip 1/4" chip cameras. It's only when you intercut the footage with bigger cameras that you start seeing a difference. Or, if you've been watching TV with high end footage and then see something shot with a smaller camera, you will think it's soft. Eventually, though, your eye gets accustomed to the look of whatever you're watching. Anyway, you don't shoot movies with video if high resolution is your main concern. That's what HD and film is for. Your 1/4" chip camera is probably about the same quality as the old VX1000, and look at all the world famous art house movies made with that camera.