THX Optimode


Prominent Member
Oct 24, 2002
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Can someone please tell me why some players can display
the drop shadow of the THX logo in the optimode video test
and some can't.
My old Samsung 709 could but my new Toshiba 220 cannot.
NTSC, the television system used in America, uses a brightness value of 7.5IRE to indicate the total absence of light (ie. black) and 100IRE to represent maximum brightness (white). For PAL and Japanese NTSC, 0IRE is used as the black or 'pedestal' level. Because 0IRE and 7.5IRE both represent the total absence of light for NTSC, many DVD players do not accurately reproduce any material below 7.5IRE (called 'below black').

The THX Optimizer test pattern you mention is a variation of the standard PLUGE test pattern. It includes material that displays at around 3.5IRE, 7.5IRE and 11.5IRE (the letters, 'THX', are around 11.5IRE, the general background of the pattern 7.5IRE and the drop shadow around 3.5IRE or so).

If a DVD player is incapable of displaying below black, then it will only reproduce the letters and the background accurately and not the drop shadow.

Below black allows easier calibration of brightness, but that's all. As there isn't any material of importance present below 7.5IRE (since there can't be anything blacker than absolute black: 7.5IRE), not being able to reproduce it makes no difference when playing ordinary DVDs.

To answer the question more simply, some DVD players don't reproduce the drop shadow because they don't have to. They're not going to come across this level on any actual DVD, just test patterns.

Thanks Adam.
I did think that I might be missing out on some
resolution but your explaination has come as a
Hi Adam,

What sort of players will display the drop shadow? In other words, how high end does one have to go in order to see this? Is it only the very top of the range players or does it just generally vary between manufacturers?

It varies, and not according to the price of the player. Early Panasonics weren't capable of reproducing blacker than black, but all of their newer models can. Sony's first generation players (1997) were capable of reproducing blacker than black, then their second generation players weren't and their newer players can again (deep breath). Pioneer players all pass blacker than black as far as I know.

Toshiba have in the past advertised that all of their players are able to reproduce blacker than black, which makes bowenjones' problem a bit puzzling.

The shadow definitely isn't there - region 1 ntsc or region 2 pal.
Perhaps Toshiba has changed the specs again.
My Pioneer dvd 525 can not display the drop shadow!
Does the new Sony 905 show this drop shadow does anyone know for sure?
My cheapie chinese dvd player displays the drop shadow and all 10 black boxes on thx optimiser,plays ntsc prog scan and to my amazement pal prog scan as well,although it wasn`t advertised with this feature.Not bad for 125 squid!!!
Any idea why my new Sony KV-36FS76U will not display the THX drop shadow when my previous KV-32FQ75 would, both from the same DVD player..?
I think you'll find that the optimode is designed for the disk it is on - abd some show the drop shadow and some don't - all on the same set-up.

Use something like Avia or Video essentials for calibration, as they'll be consistent, though you have to calibrate for PAL or NTSC unless the player has 0ire/7.5ire switching for NTSC.


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