Largest DVD Screen

Johnmb

I was just wondering if anyone could tell me what the largest screen size is that will maintain the picture quality of an average DVD? I couldn't find anything by a search on this forum, other than the projector thread, but that was more focused on the maximum size of the screen the projector could generate, rather than the maximum size of screen the DVD was designed to be shown on. I'm not necessarily thinking about projectors, I seen a 60" T.V. a few weeks ago, and they're getting bigger too, so I just wanted to know at what stage is it "too big" for picture quality purposes (and if that changes according to the T.V. technology, what are the limits for each type?).

Thanks.

robbie1876

Hi John,

It's an interesting topic you have brought up. Basically, you are wondering how big a screen can be before you start to notice pixellation or distortion when watching a DVD? That's what I think you mean, but please correct me if I'm wrong!

A DVD disk is recorded in 720x576 pixels (PAL) or 720x480 (NTSC). 'Standard' TVs generally operate on a resolution of 720x576, whilst plasma TVs and digtal rear projection TVs operate more to VGA or XVGA standards (1280x768 for example).

So if you have a 15" TV with 720 pixels and you also have a 60" TV with 720 pixels, you would be more likely to notice pixellation on the larger TV, simply because the pixels have to be bigger, because the screen is bigger! What was the model of the 60" TV you were looking at? I'd like to look at the specs before I can say for certain if you would notice pixellation or not.

If it is a plasma or digital rear projector that you are looking at, you can improve your picture substantially by investing in a 'scaler'. What a scaler does is takes the incoming resolution from your DVD (720x568) and outputs in the best resolution that your plasma can accept (1280x768 for example). It does this by using a powerful algorithm to determine what pixels need to be added to bring the resoultion up to what is needed. It doesn't just take the 720x568 format and stretch the picture up to 1280x768. It intelligently adds pixels where needed. For example if, from the DVD source, there is a red pixel right beside a green pixel, the scaler will add a cyan pixel in between. By doing this, the resolution improves and the chances of you noticing pixellation are greatly reduced.

I don't think I explained that very well, but I hope you get my drift! Please feel free to ask for further clarification.

On very big screens such as projector screens, you can go one step further and invest in line doublers or line quadruplers. They pretty much do what they say they do, by doubling or quadrupling the amount of lines and therefore the resolution before the picture gets to your projector.

So the answer is that if you plan the system right and make sure that you feed the right format picture to your tv/plasma/projector, you shouldn't notice any pixellation at all, no matter how big the screen. If you just hook up a bog standard DVD player to a projector using a cheap composite cable, the picture will be bad, and you will notice pixels.

Hope this helps to answer your query a bit!

Robbie

Johnmb

Thanks for your reply Robbie. Am I right in thinking that the largest screen that can be viewed will effectively be down to the individual (how far I sit from the screen, how good my eyesight is, etc.)? From what you have said, there doesn't seem to be an "optimum" size, it is just a trade-off between size and quality for every T.V.

robbie1876

I don't think it's down to the individual and how far you are sitting from the screen. The image on your screen will either be clear and sharp or not, no matter how far back from it you sit. Is there a particular situation where you have noticed a problem? Have you been in a showrooms and noticed that the picture looks really bad on a particular large screen?

As a general rule for 'optimum' viewing, you should be sitting about 2.5 times the screen's width away from the screen. So if you have a 60" screen, you should be sitting 150" away from it. Of course, the situation will be different in every room depending on the layout of the room, furniture etc.

There isn't necissarily a trade off between the size of a TV and the quality of picture. It is more to do with the quality of individual TV, and how well it is able to cope with high resolution DVD images. For example, this Sony has a 50" rear projection display and costs about €4500. To my eye, the picture on this model was ok, but not outstanding. When I ran a DVD into the TV, it looked pretty good, but when close to the screen you could see problems with colours bleeding, jaggy edges and movement 'ghosting'. In comparison, the Sim2 RTX55 has a 55" rear projection display and costs about €14000. This TV is pretty much perfect in every way, I've never seen a picture as good on any other tv/plasma/projector set up. You will not not see any drop in resolution by sitting closer to this TV. So the old 'get what you pay for' cliche comes into it. It's more to do with the quality of the individual TV than how far away from it you sit.

Robbie

Johnmb

Thanks again Robbie. I have noticed some problems with picture quality in some showrooms, but that has been to do with set-ups etc, as the models were the same. I didn't see the 60 inch T.V. while turned on. The main reason I asked was because I was on two minds whether or not to get a 60" if the picture quality was good. Originally I was planning on getting the largest top quality T.V. I could afford sometime next year, but if I had been told that (say) 55" was as big as you could go while maintaining picture quality, then I'd go for that now. Having read your last post, I'll wait until next year, and get the most expensive T.V. I can afford. €14000 is a little more than I was planning, but you never know, a Lotto win could be on the cards