Author Topic: DP600 backlight, DP200 backlight and contrast  (Read 3988 times)

ET

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DP600 backlight, DP200 backlight and contrast
« on: September 12, 2012, 09:35:15 PM »
DP600 backlight:
In guide, you can set the backlight, with 0 being the darkest and 100 being the brightest.
I've found that this is not linear at all: 90% of the light coming out is set in the first 0-10, and 11-100 does almost nothing at all.
http://www.imgjoe.com/x/dp600backlig.png
Has anyone else encountered this?
Is this how it's supposed to be from the factory, and if so, does anyone have a GUIDE page/componenet/whatever that will scale this so that it's linear with 0 to 100 being roughly equal increases in brightness?

DP200 backlight and "contrast":
The construction of the backlight and how it relates to the DP200 seems wrong to me.
When you use the backlight, a large amount of light spills out of the sides of the screen, into the users eyes, partially defeating the purpose of using a backlight at all.
http://www.imgjoe.com/x/dp200backlig.png
Also, the 'contrast' setting in the DP200 GUIDE page is pretty misleading.
Contrast as far as I've ever seen it used in computers, videos, and cameras, refers to the difference in brightness levels between the minimum and maximum brightness settings/pixels/whatever you're talking about.
This picture, from the Wikipedia article on contrast (http://en.wikipedia.org/wiki/Contrast_(vision)), sums it up nicely; basically, more contrast means whiter whites and blacker blacks, but you lose the spectrum in between.
http://upload.wikimedia.org/wikipedia/commons/2/20/Contrast_change_photoshop.jpg
However, the 'contrast' setting in the DP200 is more like a brightness shift, where you either move ALL things towards the white end or the black end, but the brightness levels in between stay the same distance apart.
This is sort of like messing with the exposure time on a camera: you can either overexpose everything and lose the detail in the whites, or underexpose and lose the detail in the blacks.
Shift it far enough, and the DP200 shows nothing but all black pixels, or all white pixels across the entire screen.

Lastly, both the backlight and 'contrast' settings in the DP200 GUIDE page are completely undocumented.
Luckily the backlight is mapped from 0 to 100, full dark to full bright, but the 'contrast' seems arbitrary.
A value of 0 is the default in GUIDE, -1700 is full white pixels, +1200 is full black pixels, and -900 to -500 is about right, depending on the backlight level.
Both should be documented on the GUIDE page for the DP200.
It would also be handy to have an actual contrast setting, and rename the current 'contrast' to 'brightness shift' or something else equally descriptive.
« Last Edit: September 12, 2012, 09:40:41 PM by ET »