I have a Samsung 27" HDTV (4:3 if that matters), but have noticed some slight image distortion, and I’m wondering if it’s normal (I’ve noticed it mostly on 480i, 480p images, but I haven’t really been able to test higher resolutions that much).
Specifically, it looks like the image is being contorted on a vertical column on the left side of the screen. It’s like the image is going over a bump. It’s most noticable when something 2D is scrolling across the screen, such as a news-scroll, or a 2D video game, like Mario.
It’s hard to describe the exact problem, but I’ll try my best. Imagine you pull a piece of paper along a flat surface; it should look fine. However, if you pull that same piece of paper over a bump (like a speed bump), the image on the paper will look distorted as it passes over the bump. Does that make sense?
Anyways, I’m just wondering whether this is just a quirk of the way my TV works, or whether it’s a problem that can be repaired. I should note that this is my second TV from Samsung with this problem (the current one replaced the old one that died during a power surge).
Do you have anything electronic near your TV that is perhaps not normally related to audio-visual equipment? Like a lamp or a stereo speaker? It mmay be caused by interference.
‘Speed Bumps’ is a common distortion on larger sets especially HD sets and is a geometry issue. The vertical spacing is not equal across the height of the screen.
It is most noticable during movie credits that scroll up the screen. It appears that the credits are moving over speed bumps at certain locations on the screen.
On both my TVs (which are traditional HD rear projection CRTV units) I own the service manuals (available on the intrawebs) and fixed it myself by creating a ‘grid’ on a piece of mylar film and placing it over the screen. Then via the service menu, you can set the vertical spacing to match the grids. The grids are also available on the web for most TVs.
I am not familiar with the Samsung to which you you refer but it sounds like you need to get the service manual to get into the ‘secret’ menus that let you do such stuff.
Are you sure your screen is 4:3? I thought HDTV’s were all 16:9.
Usually the problem (not rellay a problem but a side-effect) is that you have it set up to take a standard-def picture in a 4:3 format, and have it stretched onto a 16:9 screen. But instead of stretching the picture evenly they stretch the sides more. Then when an object passes left to right it stretches on the sides and compreeses in the middle.
If you really have a 4:3 screen maybe you are getting the opposite effect? Taking a hi-def 16:9 image and compressing it from the sides into a 4:3 image.
This would cause the objects to appear mormal in the center of the screen but compressed on the sides.
I turned pretty much everything off, but still had the same problem. I’ve actually had his problem in two different houses now (just moved), so I’m pretty sure it’s not local interference.
Yup, a “slimfit” CRT.
Hmm, interesting. Only thing is, my HDTV isn’t huge (27", but maybe that still applies), plus the “speed bump” is actually a column, and thus it wouldn’t really affect the appearance of credits, unless of course they scrolled left to right
Well, HD signals are all 16:9, but not all HDTVs. Mine’s actually really new (less than 6 months), and I intentionally opted for a 4:3 as I got more screen real estate for the buck (Essentially, I still get fullscreen 4:3 content of course, and the widescreen content is letterboxed).
If the problems is as it sounds to me, you may have interference on the vertical deflection.
The picture on the CRT is painted by a bright dot that is steered across the screen, left to right, to form a line. This is called the horizontal deflection. A second circuit (the vertical deflection) moves the dot vertically at a slower rate to cover the screen with lines.
These two deflection circuits in your televison receiver are synchronised by the signal sent out from the TV transmitter, so that they make a coherent picture.
It may be that the vertical deflection is getting some interference that wiggles it up and down at a certain time in each line. A single horizontal line would have a vertical ‘bump’ in it.
(Essentially, I still get fullscreen 4:3 content of course, and the widescreen content is letterboxed).