SD or HD: down and dirty down conversion
by Walter Graff (2003)

I remember in 1986, I was working in a post production facility in NYC. We had received some footage from NBC for an Olympics edit session. I was told this footage was shot by NHK and that it was a new form of high definition television that had to be converted to NTSC in order for me to view it. One thing I never forgot about this footage was that although it looked nice, I couldn't tell if it was any higher definition than regular old pictures.

Fast forward seventeen years. I now shoot high definition TV. And I am still seeing the same result; stuff that leaves the high def world (aka down converted) doesn't look like HD anymore. Yes, when I see the blur effect (aka 24p) applied to high def, on a down convert, I still see that faux film look, but I just can't seem to notice any appreciable difference in stuff shot on high def and down converted to NTSC in terms of perceived resolution. I watch The Tonight Show with Jay Leno every now and then, and I know that show originates on Sony hi-def, but I just don't see a difference in what one might call resolution, or sharpness, or detail. Of course if you have an HD tuner and the source you are watching it on is actually HD then you will see the difference. Some folks claim that HD sets alone look more like HD. But that is simply because they are higher contrast than Standard Definition sets. COntrast is more important to your perception of resolution than is resolution. In fact one of the secrets to what puts the "H" in HD on your expensive set has more to do with contrast ratios than sets of numbers folks like to throw around.

Recently, I saw a thread on the web about whether down converted HD to regular old TV looks any better than good old regular video. It seems I am not alone. A few others asked the question, why doesn't it look much better down converted. So I did an impromptu test this afternoon even though I have four projects with serious deadlines to complete. Seems it's been bothering me lately and I thought I'd have a bit of fun and show you folks what I often do; I'll test any theory that is proposed that I do not have an answer too, even if it means putting my paying work on hold. Talk is cheap and unless you try it for yourself, you will never have an answer.

So as this is impromptu, there will be no smiling faces, no explicit sexual shots, but merely one simple daylight shot, looking out of the window of my office at Manhattan. I used this shot because it has all the elements I need, blacks, highlights, contrast, detail. The SD shot was done with my Ikegami HLV-55 feeding RGB video to my edit system. Standard set-up, preset white balance, etc. The HD shot was done with my Panasonic Varicam camera feeding down converted RGB to my edit system. The HD camera is set so it shows regular video, no blur and nothing else applied. I am using an AJA down converter. Do different down converters make different quality pictures? Yes, but I have yet to see one used in the television business that really looked incredibly different than any other. DOes it look "better" on high def monitor? It can but as I said that mostly has to do with the monitor than the signal feeding the monitor.

I cropped the SD shot using a black mask so as to have a similar reference to the HD. Also note the HD has two vertical yellow lines. That is my down converters 4x3 safety marks which I left on intentionally since I was having a difficult time differentiating the difference between the two shots when I dumped them to my system. I made 720x480 progressive frames from the shots.

Of course this test has many holes in it including all the file conversions but in the end, if you start out with more information, you should end up with some discernable difference. About all I see is a bit more color inherent in the HD shots.

Okay! Let's take a look. I'll leave you to your own devices. BTW, the black bar in the middle of each shot is a window frame. It is not a split screen.

Standard definition

High definition down converted



Files reduced to 400x270 for comparison in the above shots. What do I see? Maybe a tiny bit of a sharper picture in the HD shot. Detail seems ever so slightly better. Remember HD always has the yellow lines.

Here are some blow-ups of the frames. See if there is any difference in the information presented. It's far from a perfect test, but even without the zooms, and the conversions the down converted HD looks like good old TV to me. Remember the black bar is not a split screen but the window frame dividing two windows.

Bigger sized versions of the above: SD shot

HD shot down converted

And the following are split screens and zooms of various parts of the pictures

Would a Sony F900 camera look any better? No. I tried that the other day and set up both the 900 and the 27 side by side on my last job where I was using both and got a shot of the MIT campus that I was going to include it in this demo but the HDCAM footage got corrupted on my edit system and I no longer have the Sony deck for playing back HDCAM so I can't recapture the footage.

Copyright 2013 by Walter Graff. This article may be circulated and shared as long as the following reference is made: 'This article appears courtesy of Walter Graff-'

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