3D TV Health Scare Shock

[The_Lhc]

JohnDuncan:the_lhc:
Andrew Everard:* Note that watching TV while sitting too close to the screen for an
extended period may weaken your eyesight

Please, this is an old wives tale isn't it? Don't tell me my mum was right all along!

Well I've found she was wrong on the other warnings she gave me about my eyesight.

Anyway, what are you doing talking to my mum about these things?

 

[Andrew Everard]

Panasonic did give a kind of answer in its 3D seminar at CEATEC last autumn, as I reported in this blog piece:

'How long can one watch 3D with the special glasses without eye-strain? "The viewing time upper ceiling is the same as a movie in a theatre - around two to three hours."

At this, one of the US journalists got rather over-excited: "Are you suggesting that after two to three hours eye damage will occur?" he asked.

No, that's not really what we said, was the answer, and I think the response to his later "I feel I must clarify..." was along the lines that no, your head won't explode either.

Probably.'

 

[sonycentre]

Its all to do with the various companys covering themselves,all game consoles give warnings,even sky give warnings on certain programmes/films that have flash photographie,flashing imagies.........better to be safe then sorry.

 

[Sliced Bread]

It's not just a-covering. It is also necessary.

My friend is (very) epileptic and she has to rely 100% on these warnings. If she watches flashing in a programme either as a result of missing the warning or because there wasn't a warning, she gets incredibly painful headaches or fits. Once triggered the fits can go on for a LONG time.

For people in that position, these warnings are very important.

 

[visionary]

Sounds to me like "they sound the same so they must be connected"

In ophthalmic terms we talk about a phoria and we mean a misalignment of the eyes in their resting state (think of the tracking on your car). If someone has an exophoria then their eyes have a tendency to drift apart, an esophoria means they tend to drift together. In either case the eyes will stay aligned if they are both looking at the same thing. If they don't stay aligned (like Marty) that is a tropia or squint.

If the brain is struggling to align the two images because of this, we talk about a de-compensated phoria and may use prisms in a pair of spectacles to "push" the images back into alignment in the visual perception.

Placing stress on the visual system can cause a previously compensated phoria to de-compensate and cause eyestrain symptoms. Looking through funny coloured or polarised spectacles is deliberately dissociating the pictures from the two eyes in order to create a 3D image in a 2D plane and this might cause de-compensation but it would be temporary.

If your eyes don't focus together because your spectacles are out of date or because you need glasses but didn't realise this may cause similar symptoms which, again, may be exacerbated by wearing 3D specs.

 

[scene]

JohnNewman:It's not just a-covering. It is also necessary.

My friend is (very) epileptic and she has to rely 100% on these warnings. If she watches flashing in a programme either as a result of missing the warning or because there wasn't a warning, she gets incredibly painful headaches or fits. Once triggered the fits can go on for a LONG time.

For people in that position, these warnings are very important.

I too have a friend with (now fortunately controlled by drugs) epilepsy and know how important appropriate warnings are for photo-sensitive epilepsy.

However a statement of the form:

*Photosensitive seizure warning... some viewers may experience an epileptic seizure or stroke when exposed to certain flashing images or lights... even those without a personal history may have an undiagnosed condition..*

Are veering into the a-covering variety.

Though I do like the:

* Some 3D pictures may startle viewers.

That's a real gem. I can think of lots of current 2D films that should include that warning...

 

[The_Lhc]

sonycentre:even sky give warnings on certain programmes/films that have flash photographie,flashing imagies

You've never watched terrestrial TV then?

 

[Anonymous]

Do cinemas refuse under 5s from all those 3D cgi cartoon movies. 3D is gimmicky appealing to children and relatively easy to add to animation. With small children the your older sibling can watch it but you can not is not going to go down well.

The shutter glasses flickering could be a problem for some people with eplipsy. Since some could not watch CRT at all or could only watch black and white.

Most people can not detect flicker above 75 frames per second. So glasses with 120 frames per eye per second look likely to be flicker free and will be even pull down with 24fps sources so no added motion judder. But some glasses might be as low as 60 frames per eye per second. This is the same as NTSC CRT refresh rate, but peripheral vision is more sensitive to flicker than central vision, and the glasses cover the whole eye so room lighting may appear to flicker.

 

[Andrew Everard]

But then cinemas don't use the frame-sequential technology employed by most domestic 3D TVs, and thus don't require the active shutter glasses.

 

[Anonymous]

Andrew Everard:But then cinemas don't use the frame-sequential technology employed by most domestic 3D TVs, and thus don't require the active shutter glasses.

If they use a single projector they are sequential. The difference in glasses is purely down to cost of implementation. RealD 3D typically is a single projector with a rapidly switching polarizer at the projector. Dolby 3D is typically one projector with a rapidly rotating color filter. Xpan 3D uses shutter glasses. The reason for 3D cinema having a much lower reference white level than 2D is so they can get away with using one projector.

 

[Andrew Everard]

Yes, of course all movies, and indeed TV pictures, use sequential frames. But apart from the 3D TVs now being introduced, you don't have two shutters constantly flickering in front of your eyes. You may just as well say people shouldn't watch TV because it comprises rapidly changing images.

 

[Anonymous]

The reason they warn against under 6s watching 3D appears to be due to the use of binocular disparity without accommodation. The eyes think the object is changing distance due to binocular disparity, but the focal distance to the image remains the same. The link between binocular disparity and accommodation of the eyes lens is learnt, but once learnt can not be disassociated by adults hence the possibility of eye strain. If children in theory learnt that the link was not reliable it could in theory impact their depth perception. Any flickering should be a non-issue unless the child has undiagnosed epilepsy.

3D uses binocular disparity to fool the viewer. But studies on the difference between distance guessing with binocular and monocular vision appear to indicate lens accommodation is the main distance cue used by the eyes/brain when in lacks other context cues in the image.

The effect of having the projector alternating polarization of the image causing the viewers glasses polarizers to constantly flicker black/image or a 3D TV viewer using active shutter glasses to constantly flicker black/image, is the same. Shutter glasses are actually superior as they prevent any leaking of the incorrect image causing ghosting, double images.

 

[Andrew Everard]

Thinks: Should never have picked him up over 'incredulous'...

 

[scene]

Andrew Everard:Thinks: Should never have picked him up over 'incredulous'...

 

[Anonymous]

Andrew Everard:Thinks: Should never have picked him up over 'incredulous'...

, well knightout is the first person ive seen that has made you look up the oxford english dictionary andrew , lol , props for that

 

[Andrew Everard]

Hardly...

 

[visionary]

It is also concievable that, if you have a child with anisometropia (unequal focus) and/or barely compensated heterophoria and you stress the visual system by dissociating them, you may cause a breakdown of binocularity and induce a squint. After the age of 8 the visual system is less plastic and better able to cope with this kind of issue.

 

[Anonymous]

when you think about it , watching 3d tv , using the active glasses , will give the eyes and brain a different experience , i mean , is anything one would be likely to see in normal life , similar to the 3d affect ?? maybe those warnings are justified ...

 

[The_Lhc]

maxflinn:when you think about it , watching 3d tv , using the active glasses , will give the eyes and brain a different experience , i mean , is anything one would be likely to see in normal life , similar to the 3d affect ?? maybe those warnings are justified ...

I know what you're saying but the above does remind of the time Scott Mills sent one of his team to "Stupid Street" with a pair of 3D glasses and asked various people if they fancied seeing in 3D all the time, and not just at the cinema.

A LOT of people said no!

 

[Clare Newsome]

visionary:
After the age of 8 the visual system is less plastic

....unless you're Mr Potato Head

 

[Andrew Everard]

Hence, I think, the warnings about what's being called 'binocular dysphoria'. In real life, your eyes have to process the relative distances of things they're seeing, thus giving us our perception of distance.

The theory goes that because 3D does this for you by creating an illusion of depth, the eyes stop doing it, with claimed consequences being everything from minor parking accidents in cinema parking lots at the end of 3D movies to more long-lasting versions of the same effect after prolonged and repeated exposure to 3D.

At least that's what's being suggested in some quarters...

 

[Ravey Gravey Davy]

I can see that all the 3D TV reviews in WHF are going to have 2 columns headed "Specs".

 

[visionary]

Ravey Gravey Davy:I can see that all the 3D TV reviews in WHF are going to have 2 columns headed "Specs".

Would that be the "in-depth" reviews?

 

[Anonymous]

well i guess using these active glasses , is going to be a unique experience , i wonder how long this thread may be in 12 months ?? gel , what have you started

 

[Anonymous]

the_lhc:
maxflinn:when you think about it , watching 3d tv , using the active glasses , will give the eyes and brain a different experience , i mean , is anything one would be likely to see in normal life , similar to the 3d affect ?? maybe those warnings are justified ...

I know what you're saying but the above does remind of the time Scott Mills sent one of his team to "Stupid Street" with a pair of 3D glasses and asked various people if they fancied seeing in 3D all the time, and not just at the cinema.

A LOT of people said no!
reminds me of the time we sent a guy to buy some tartan paint , he actually asked for it