i have posted this on several forums except remotecentral and no one has answered.

i noticed that when i am watching something that has a close up, the background maybe blurry. this happens on any source i am feeding my hdtv widescreen.

is this normal? i noticed that in magazines the pictures exhibit the same charecteristics. the picture in the frontground maybe sharp, but objects in the background may be blurry.

it's driving me crazy because I don't kow if to return my tv set or not.

slocko,

The phenomenon you are describing is called 'depth of field' it takes place in photography as well as cinematography. The lens on a camera can only focus on a certain point. Depending on variables such as the focal length of the lens, the aperture setting (the opening in the lens that lets light in) and the exposure time, the amount of background that is in focus varies.

This message was edited by Don H on 01/08/02 03:30.39.

I think your TV is OK, but you bette return your magazines! :)


Don's explanation is right on. The human eye is the only lens that I know of that focuses at multiple depths at the same time.

thxs!!!!!!!

i think i will get my eyes replaced :)

good thing I postponed the delivery of the replacement tv. now that the tv has 100 hours it's starting to come in to it's own and looking spectacular.

To answer your question.

is this a dumb question?

Yes!

Do you mean to tell me that you never noticed that background images are blurry? Hold your finger a couple of inches from your face and look at it. Wow! your finger is in focus but everything behind it isn't. I'm not trying to be completely obnoxious, well yes I am. Its just that my jaw dropped when I read your question.

Steve13

"The human eye is the only lens that I know of that focuses at multiple depths at the same time."

You must have special eyes. The human eye focuses like a camera. What your eyes focus on is what is in focus everything else is blurry or out of focus.

when i look around me everything looks in focus. of course if i stare at my finger then objects will look blurry behind it. but when i see tv i am expecting to see the same thing i would see if i was looking out a window of the same size as the screen.

what was confusing me, was the camera focusing in on something, but i guess it's so gradual that you don't notice it. all of a sudden i am looking at the scene behind the person and it's out of focus. the camera might be focusing on the object, but my eyes are not. i am just taking in the entire scene.

since this is a new widescreeen hd tv mated to a progressive dvd player i was looking very carefully at everything to enjoy the level of detail that i didn't have before.

i start asking everybody and no one could tell me if it was normal. i got paranoid!!!!! so even though it might have turned out to be a dumb question, i'm glad i asked because now i can enjoy my tv!!!!

Slocko:
Dude, your question is [u]not[/u] stupid. It is a normal question and worthy of a normal answer.

There is a lot more going on in your perceived vision than most people realize. You eyes will "twitch" under normal circumstances. This twitching is normal and (usually) microscopic. The changes in where your eyes point work in concert with your brain's processing to increase the perceived resolution of your vision. Your eyes also shift focus on a constant basis as well to increase the perceived depth of focus.

Camera lenses do not do this "twitching" or "dithering", and since you are looking at an image these cameras captured, you are subject to these limitations.

If you doubt that your eyes do this as a normal function, there are eye drops you can use that will temporarily halt these muscle responses. Get your opthomaligist (sp?) to use them on you as an experiment. I don't remember the name of this class of drugs, but they are often used during LASIK surgery to keeps the eye immobilized while the laser vaporizes your cornea. You wil notice a very drastic reduction in your vision accuity.

BTW, I'm not a doctor, and I don't play one on TV.

Slocko,

Once again, not a dumb question. Most people don't notice the phenomenon of 'depth of field' in movies or photos, except when we do something like buy a new HDTV, or perhaps a camera, and start scrutinizing the image to see just how much better the quality is. I thought I'd post a response here, as an amateur video editor and photographer, to touch on the artistic aspects of why this phenomenon is desirable. Obviously, the director of a Hollywood movie or a professional magazine photographer would not let a 'blurry image' slip into their finished project, if they did not intend it to be that way. Focusing on a subject in the foreground, and using a camera setting which blurs the background, is a quite common technique to emphasize the subject of the movie or photo, and most people tend to see these images as having a professional look to them...even if they can't quite explain why.
And this isn't really due to any limitation of the lens or equipment...its quite easy to make a camera which has quite a long focal length. Most cheapo film cameras do this, and for good reason...many amateur photographers wouldn't know how to focus a camera if that option were available...they are only taking snapshots, and are happy when everything comes out in focus in their pics of mom and the kids at Disneyland. But if you had a professional portrait made of, perhaps, your bride to be, then most likely the photographer would have a very expensive camera with which he could control many aspects of the process, including focusing and depth of field...and he would probably blur the background. And that would be a good choice, because you'd want the emphasis to be on your bride, and not on what might have been going on it the background of the park where he took the photo. The directors of the movies we watch on DVD use similar techniques, and other focus tricks to add artistic flair to their movies. (i.e. soft focus....blur everything, including the foreground, to hide unsightly wrinkles in aging actresses's faces; or deep focus...which uses a really small apature setting to set everything into focus the foreground and the background...a good example of this is in Raiders of the Lost Ark, when Indy is talking to Belloq in a restaurant...Indy's face is very close to the camera...and Belloq is perhaps 20 feet away in the background, yet they are both in focus. S. Spielberg did this intentionally, because it was a technique which hearkened back to the cinema period he was homaging with this film, i.e. the movie serials of the 30s and 40s, when deep focus was used quite often to show off the recently developed lenses which could produce such a deep 'depth of focus.'

thanks gents. i am enjoying my tv very much!!!!!

Neither am I, but I did stay at a Holiday Inn last night!

Larry
www.fineelectricco.com

Yes, my eyes are special!! :)

Maybe a better way to say this would have been to say that the human eye (and the brain behind it) has the ability to focus on different field depths in rapid fashion, making it seem as if everything (near and far) is in focus at the same time. A photo or single film frame is a static image and more clearly demonstrates the focus/depth of field issue.