The actual quality of HD

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ajobbins

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#23204 21-Jun-2008 23:02

Interested to see the actual between a 720P HD image and a SD one I did some investigating. I was watching the movie 300 today in 720P on my Laptop (Laptop only has 800 vertical res) and took a screenshot.

I then used that screenshot to make 2 high res JPGs. One with 800 lines (So slightly stretched 720P) and one with 480 lines, what you would get with broadcast TV.

Viewing them both fullscreen (The full res one at 100% and the 480 lines on scaled to fit the screen) there is VERY LITTLE percievable difference between the two.

Sure you may see a noticble differnce with a very large screen, but from what I have seen, there doesnt seem to be that great a benefit in terms of percievable quality of HD over SD.

Tests hardly scientific, and source material (.mkv BluRay rip) probably don't help, but this is how it seems to me.

Thoughts?

(Screenshots of my screen showing each of the images: Full Res | 480 Lines)

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#139642 21-Jun-2008 23:09

Looking at the two images on my 24" monitor, there is noticeably greater detail on the High Res. version, particularly in the skin patterns above and to the left of the eyebrow. With portions of the image that aren't in such sharp focus, the difference is much less noticeable.

I think it would take a screen larger a typical laptop's LCD in order to see the difference. It's certainly very noticeable on my monitor.

Fossie

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#139653 22-Jun-2008 00:38

Big big big big big difference. If you watch true 720p on an HD tv, you will be stunned.

ajobbins

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#139668 22-Jun-2008 08:08

I watched it on my 32" Bravia. Not the biggest screen I know but even sitting up close it was only marginally better looking than a DVD over component.

Dingbatt

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#139686 22-Jun-2008 11:02

adamj:
I then used that screenshot to make 2 high res JPGs. One with 800 lines (So slightly stretched 720P) and one with 480 lines, what you would get with broadcast TV.

When you say hi res JPGs do you mean 0% compression? As JPG is a lossy compression codec you may have, at least partially, invalidated your test. How do the file sizes compare?

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ajobbins

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#139688 22-Jun-2008 11:13

Well I cant tell the differnce between the 32bit bitmaps I orginally saved the screenshots at, and these JPGs.

I couldnt do a Screenshot straight from playing the BluRay disk (Computer just produces a completely black screenshot, which I guess is a copy protection thing?) so I had to use a .mkv backup I made, which is obvioulsy going to be somewhat lossy itself, so totally not a scientific test.

It certainly was very clear, but not as contrasting as I would have thought. My TV is only 32" tho...

Nety

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#139689 22-Jun-2008 11:20

Suggest you do some reading as it is the only way to really understand why what you did does not really work. Resolution is only one of the differences and the test you did does not treat that correctly anyway as for a start you used jpeg which compresses the image.

Also what was the source for 300? was it blueray or a rip? If it was not blueray then it has been compressed and is not giving you a true Idea of what HD is like.

Start here

http://en.wikipedia.org/wiki/High-definition_video

But there are may other resorces that will give you a better idea.

The bottom line is going and seeing for yourself. Find a shop that has a GOOD setup (hard to find) then compare a DVD and HD source. It will blow you away. Well that is providing they have not botched it which most shops do.

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Nety

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#139690 22-Jun-2008 11:23

Sorry missed your last post which answers some of my points.

One other major that you missed is color depth which is also a big part of what makes HD different.

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ajobbins

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#139691 22-Jun-2008 11:30

Nety: Sorry missed your last post which answers some of my points.

One other major that you missed is color depth which is also a big part of what makes HD different.

Cheers for the info :)

sbiddle

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#139702 22-Jun-2008 12:34

Trying to compare the difference with a single shot that is particularly dark isn't very scientific.

Once you have watched HD content on a decent size screen (50" or so) there is no going back. The difference between s very good HD show such as Rove recorded off Freeview|HD and regular Freeview and played back on the same PC is very obvious.

stuzzo

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#139753 22-Jun-2008 16:43

Nety:

One other major that you missed is color depth which is also a big part of what makes HD different.

Not really sure if this is true. Both DVD and Blu-ray, for example, have 8-bit colour depth and the colour spaces used are quite close with their primarys.

There might be more headroom used in the whole process of producing HD material though.

Fossie

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#139756 22-Jun-2008 16:46

8 bits per color? Being 8 for each of RGB..? Being 24 bit?

stuzzo

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#139757 22-Jun-2008 16:51

DVD and Blu-ray both use 8-bit per colour 4:2:0 formats.

paradoxsm

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#139769 22-Jun-2008 18:19

I certainly notice the difference, also the SD version has thes two bits of compression artifacts near the nose (blue flecked squares)

It often depends on the television being used.

sbiddle

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#139773 22-Jun-2008 19:01

Even on my 17" LCD here opening up both pictures in their own window and switching between them it's very very obvious. The HD picture is so much sharper. The skin texture is so much more detailed.

STI

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#139775 22-Jun-2008 19:23

The difference isn't obvious at first for me on my 17" monitor running at 1280x1024.

Found this site which compares DVD picture quality of Fellowship of the Ring to sampled down HD DVD screen captures of the same film. In that case the difference is quite noticeable and amount of detail on HD is amazing.

What do you guys think?

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