V1040 Black and White mode

[Damian]

I have a potential application for a V1040, however the customers application is in a dark room making a film product that may be susceptiuble to pre-exposure if exposed to certain wavelengths of light. They use old monochrome screens (black and white) and that seems to be OK for them. They are insisting on a minimum 10" screen. Is their anyway to put the 1040 in black and white mode? If I restrict myself to black and white HMI objects, I am curious as to what whter the new LED screens arne't actually creating white by mixing all wavelengths.

Any advise?

[Emil]

Hi Damian,

White is always a mix of several wavelengths. This is phisics! If the spectr of white LEDs is diferent from the spectr of flourecsent lamps - I don't know. If I'll try to contact producer and find the spectrum, will this help?

BTW - you can control backlight intensity in steps from 0 to 100.

If the photo material is sensitive to some colors, you can make HMI, avoiding these colors. This sounds to me better soluion than B/W. I remember the old dark rooms had red ligths. So maybe you can design the display in variations of red?

[Damian]

Hi Damian,

White is always a mix of several wavelengths. This is phisics! If the spectr of white LEDs is diferent from the spectr of flourecsent lamps - I don't know. If I'll try to contact producer and find the spectrum, will this help?

BTW - you can control backlight intensity in steps from 0 to 100.

If the photo material is sensitive to some colors, you can make HMI, avoiding these colors. This sounds to me better soluion than B/W. I remember the old dark rooms had red ligths. So maybe you can design the display in variations of red?

Hi Emil,

Thank you for the quick response. I agree, true what light is a combination of all the wavelengths, but it was why impression that white LEDs were manufactured to a very specific narrow band of Yellow and Blue that fools the human eye.

[Damian]

Sorry, wasn't finished typing.

You also bring up another very good point I didn't consider. The backlight itself may be a source of different wavelengths as well.

I like your idea of say restricting myself to red. If I do restrict myself to a certain color, am I assured that only the RED emitters are operating, and NOT some tiny percentage of the blues and greens?

[Simon]

Colour LCDs work by filtering the white backlight to produce colour. The backlight is always on and the active LCD layer is used to block or allow light to pass through the red, green and blue filters. Each pixel is a group of these filters. For example the red colour is produced by switching on only the parts of the pixels with red filters. One weakness of LCD is that when the pixels are switched off a very small amount of light leaks through, so in the case of red colour, there would also be a very small amount of green and blue emitted. THis would also be the case for the "black" areas of the screen.

As Emil suggested you can also adjust the backlight intensity to its minimum usable level.

If they use B&W mono screens then it sounds like some stray light is OK. But maybe they have a way you can run some tests?

[tmoulder]

interesting point simon, explains something I always noticed, that a black screen seems to glow in a dark room, even though theoretically it should be dark.

Thanks, Mr Wizard!

TM

[Damian]

Colour LCDs work by filtering the white backlight to produce colour. The backlight is always on and the active LCD layer is used to block or allow light to pass through the red, green and blue filters. Each pixel is a group of these filters. For example the red colour is produced by switching on only the parts of the pixels with red filters. One weakness of LCD is that when the pixels are switched off a very small amount of light leaks through, so in the case of red colour, there would also be a very small amount of green and blue emitted. THis would also be the case for the "black" areas of the screen.

As Emil suggested you can also adjust the backlight intensity to its minimum usable level.

If they use B&W mono screens then it sounds like some stray light is OK. But maybe they have a way you can run some tests?

Hi Simon,

Thanks for the lesson. I have brought up the point to the customer that the color screen may actually be better than the monochrome backlit screen they have been using. It may simply be a case of not knowing any better.

It sounds as though no matter what we use, we will have to expect some small amount of light contamination. I am going to try and get them to be more specific regarding what wavelengths they are most concerned about.

Thanks again,

Damian