Sharpness Control

[Ignacio Rodriguez]

> I wonder also if the DV codec will not work better on an image
> that has less sharpness??

I think it should. Perhaps especially for chroma which is the DV codec's main weakness. But first we would need to know if the high frequency enhancment affects chroma or only luma. Although on some posts it has been mentioned that noise increases with higher 'sharpness' settings, my tests sugges not, and this would be consistent with the edge enhancement algorithm not affecting chroma, since most of the noise I see with low light & gain up seems to be more in chroma than in luma. Of course this is all very subjective and non-scientific so I could be wrong. Anybody care to comment on this theory?

[Boyd Ostroff]

Not so good with the theoretical stuff myself, but I suggest you hook up a monitor and just have a look. Use a dimly like subject and turn the exposure wheel so you get the iris wide open and maximum gain boost. Now try turning the sharpness dial. When I did this myself I noticed less grain with sharpness set to the minimum than I did when it was set to the default.

[Gints Klimanis]

>When I did this myself I noticed less grain with sharpness set to >the minimum than I did when it was set to the default.

Boyd, this would still be a tough test. If the negative settings (those less than 0) actually put the Sharpness filter into a Low Shelf Cut mode, then those settings would be blurring the image,
of course, resulting in less noise. The best method would be to ask the designer. Second that, we can grab impulse responses
of the Sharpening filter at various settings by capturing pictures of single CCD line vertical bars (black on white, or white on black). Then, a Fourier transform would yield the frequency response of the filter.

[Mike Sanchez]

Gentlemen,

I have been reading this forum for a few weeks as I learned about my TRV-950. Regarding sharpness:

When I first began utilizing the TRV-950 I was struck by how sharp the image was relative to my preceding video experience.

As a long time still imaging guy I quickly tested all the functions of the TRV with still images using all manner of test methods.....the easiest of which is the simple digital "blow up".

Below is a link to three images from the TRV-950. Minimum sharpening (full left), default (middle) and max sharpening (full right) on CUSTOM PRESET.

http://home.att.net/~colorgamut/TRV950/CompositeSharpTest.tif

The leftmost position, as one can see from the smooth gradations in tonal quality, is the native CCD response (no low pass filter is applied as far as I can tell). The middle sharpening position of factory default is riddled with noise (I will come back to the exposure settings and how they affect this in a moment). The max sharpening is too gross to discuss.

In the above image acquisition I hand held the TRV at full telephoto and acquired a still at max res and SFN. Please note that I should have used a tripod to norm out the possibility of my hand moving and motion blur. But, I was really only interested in noise. The gain up on the auto gain was +6dB.

When outdoors with good lighting the experiment is different. When there is no gain-up I use one step up from min sharpening with almost no detectable noise. When indoors (always have gain up) then I use min sharpening.

In fact, once I discovered this little SONY sharpening trick at default and the relative softness of the image without beating on it with a high pass filter I was disappointed in the resolution of the video quality relative to my expectations based on the price of the thing (the TRV cost 4X what my old Canon ES-970 cost).

Anyway....in summary, in the presence of CCD gain up I am forced to use no sharpening to minimize noise resulting in video and still softness that is apparent. The final vido resolution, when playing side by side against my ancient 8mm Canon is better. But, it is not 4X better (as was the price difference between that old Canon and my new TRV-950).

[Shawn Mielke]

Since my first, and last, post in this thread, I have come to agree with you, Mike, and Boyd. Sharpness is insultingly fake resolution, no ifs ands or buts, and it is messy, likewise. Any amount serves only to ruin images.

[Boyd Ostroff]

These are some great observations Mike! Looking at your images, it's a no brainer for me.... I much prefer the one on the left. But I think you should have used a tripod to be just a bit more scientific :-) What was the shutter speed? From your description I assume these are still images as opposed to video frames?

Now I think it's a little unfair to expect a direct correlation between price and image quality. For starters, DV has some severe limitations. Look at the quality of a still photo from your camera and compare to a frame of video. But I suspect the tape transport and other innards of the PDX-10/TRV-950 are built to a higher (prosumer) quality standard than your other camera, which I also assume is a 1-chipper.

Would you expect a $400,000 house to have four times as many rooms as a $100,000 house? Would a $40,000 car to get 4x better mileage than a $10,000 car? Maybe. But generally that isn't the way things seem to work. ;-) Anyway, I do understand your general point, and the frustration with how expensive this stuff can be! I'm very happy with my PDX-10 due to its 16:9 mode which the TRV-950 lacks. For 4:3, you might be happier with the VX-2000, but that costs even more!

[Mike Sanchez]

Boyd,

Thanks for the comments and reply. You are right....it is not really fair to expect linear mapping of price and resolution. The TRV950, because of its price and my very, very mortal bank balance, and because of many very positive reviews.....came to my door with my expectations set on high. Some of those expectations are not being met. But....others are.....

The shutter speed was 1/60, aperture was F1.6, and as noted I was at full telephoto......a compliment to the image stabilization system used by the TRV950.

I am posting a question about the autofocus system on a new thread to assess if I have a unit problem......if you have a chance let me know what you think on that thread.

[Boyd Ostroff]

<<<-- Originally posted by Mike Sanchez : The shutter speed was 1/60, aperture was F1.6, and as noted I was at full telephoto -->>>

As Tom has noted elsewhere, the data code tends to lie about this sort of thing. I don't think it's possible to have a F1.6 aperture at full telephoto, is it?. Browse back through the forum a bit for a discussion of the "double secret" internal ND filters and questionable data codes...

[Tom Hardwick]

You're right Boyd, the 'replay' display is good as useless, and my PDX10 often said I'd shot at f1.6 at full telephoto. As we all know, the maximum aperture of the 12x zoom at full tele is 1 1/2 stops less than this, at f2.8. Surely it's not beyond Sony's command of the DV language to fix this incorrect read/write? After all, their cams generally supply more information in the 'display' mode than, say, Canon do.

tom.

[Mike Sanchez]

Boyd and Tom,

I will check the files for the max aperture and am embarrassed that I did not think to question the F1.6 displayed on the screen in data code mode at full telephoto. Not one of my SLR zoom lenses maintains its maximum aperature at full tele so why should my TRV950? Anyway.....thanks.

And......I was very happy to see the data written to the screen. I think lots of the information may be accurate. I've checked the settings many times in low light and in outdoor settings to assess the auto gain-up. Seems like when I think it should be at max +18db gain it is and vice versa. In fact, I've used the display to kind of get a sense of when the aperture changes and when auto-gain up kicks in......

As Tom notes......my old 8mm Canon told me precisely nothing about the settings. I could tell when gain-up was maximum by the visual SCI FI look of large and small scale noise streaming across the screen on playback.

I would like to note: The noise level of the TRV-950 is so far below the noise level of my old Canon that I have not thought about noise since beginning to use it, except to turn off sharpening. One that is off, noise is no issue on the TRV....even in firelight......

Relative to my old Canon anyway. If I had shot with a VX2000 for the last few years I might think a bit differently.