85hz against 100hz
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Depends on the source you are watching - the "normal" human eye cannot see things change faster than about 60 Hz. That's why you probably don't see your light bulbs flickering, because the frequency is at 60 Hz (at least in the US). If you are watching a progressive scan source (i.e. 1080p, 720p, or anything else with "p"at the end), then you will not see a difference between 85Hz and 100Hz. If you are watching an interlaced source (i.e. 1080i, 480i, etc.) then you may detect a slight difference if you look for it. Maybe. I could be wrong on this next statement, but the interlacing is performed at a 60 Hz base frequency (you only get a full picture at a rate of 30 Hz), so any difference should be negligible. Size of the TV doesn't matter in this case as much as the source you are using and how fast your eyes-to-brain connection is.
As always, if this question is posed for a new purchase decision, we can talk specs and theoretics all day. In the end, TRY BEFORE YOU BUY! Go to your local "Buy More" and look at the LCDs side by side (and set the brightness, contrast, and color temp settings to "stun" instead of "kill"). See for yourself if there is a difference. Display frequency is only part of the equation to the "best picture". You usually won't go wrong if you follow this advise.
As always, if this question is posed for a new purchase decision, we can talk specs and theoretics all day. In the end, TRY BEFORE YOU BUY! Go to your local "Buy More" and look at the LCDs side by side (and set the brightness, contrast, and color temp settings to "stun" instead of "kill"). See for yourself if there is a difference. Display frequency is only part of the equation to the "best picture". You usually won't go wrong if you follow this advise.
The European analogue TV standard refreshed at 50Hz (interlaced) - the same as their electricity - and most people don't notice any flickering. Some do however.
The other thing to be aware of is that movies are typically shot at 24 frames per second. To avoid flickering, they actually double that by showing each frame twice.
In both cases, the problem is that the screen image fades then gets refreshed. This has to be done faster than the eye can see. The screen needs to be lit for most of the 40 milliseconds the eye is looking at a frame.
With LCDs you get another issue. The crystals don't respond as fast as plasma or phospors so you may get a motion ghost. While the specs tell you this shouldn't be a problem, in reality it often is. The 120Hz LCD screens now available take care of it.
120Hz is pretty convenient for bluray too. Again, most movies are shot at 24 fps, so repeating a frame 5 times gives you a good result. For TV video, shot at 30 fps, repeating a frame 4 times also nails it. This wasn't an issue for DVD because the MPEG2 encoding specified the frame rate. Bluray allows for multiple frame rates and some movies are transferred with the original frame rate intact.
The other thing to be aware of is that movies are typically shot at 24 frames per second. To avoid flickering, they actually double that by showing each frame twice.
In both cases, the problem is that the screen image fades then gets refreshed. This has to be done faster than the eye can see. The screen needs to be lit for most of the 40 milliseconds the eye is looking at a frame.
With LCDs you get another issue. The crystals don't respond as fast as plasma or phospors so you may get a motion ghost. While the specs tell you this shouldn't be a problem, in reality it often is. The 120Hz LCD screens now available take care of it.
120Hz is pretty convenient for bluray too. Again, most movies are shot at 24 fps, so repeating a frame 5 times gives you a good result. For TV video, shot at 30 fps, repeating a frame 4 times also nails it. This wasn't an issue for DVD because the MPEG2 encoding specified the frame rate. Bluray allows for multiple frame rates and some movies are transferred with the original frame rate intact.
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