Forums

Sega Master System / Mark III / Game Gear
SG-1000 / SC-3000 / SF-7000 / OMV
Home - Forums - Games - Scans - Maps - Cheats - Credits
Music - Videos - Development - Hacks - Translations - Homebrew

View topic - Game Gear LCD Blur and Possible Variations

Reply to topic
Author Message
  • Joined: 25 Jul 2007
  • Posts: 716
  • Location: Melbourne, Australia
Reply with quote
Game Gear LCD Blur and Possible Variations
Post Posted: Sat Sep 11, 2021 5:32 am
There's been some discussion recently on the Discord about how pixels, as displayed on the Game Gears 160x144 LCD, are not perfectly sharp and it has become apparent that a single pixel takes up two rows of the LCD at half brightness, pixels that converge together then create fully lit pixels with their upper and lower edge offset at half brightness.

Some of us seem to recall seeing units where this aberration was not present, but we haven't been able to find any evidence. I think we need to collect data from owners to see if the behavior is the same on all variations.

You can run the attached LCD test ROM I made, and switch between patterns, particularly the last screen with lines of different colours and orientation shows up this behavior fairly clearly.
lines.png (6.49 KB)
White Line Pattern Source
lines.png
WIN_20210911_15_19_13_Pro.jpg (143.35 KB)
White Line Pattern on LCD
WIN_20210911_15_19_13_Pro.jpg
horiz.jpg (192.18 KB)
horiz.jpg
GGScreenTest.zip (2.38 KB)

  View user's profile Send private message
  • Joined: 25 Jul 2007
  • Posts: 716
  • Location: Melbourne, Australia
Reply with quote
Post Posted: Sat Sep 11, 2021 11:09 am
We have also confirmed that there are 145 actively lit rows on the LCD, photos attached of the topmost rendered pixel and the bottom-most rendered pixel.

The picture shown for the bottom-most row shows the pixel spread across rows 144 and 145, moving its position to row 145 causes it to disappear from the display.

The service manual also states the LCD is 160x146 pixels, this can be confirmed by the additional unused row in the topmost picture.
WIN_20210911_20_55_54_Pro.jpg (75.89 KB)
Top most pixel row
WIN_20210911_20_55_54_Pro.jpg
WIN_20210911_20_58_45_Pro.jpg (79.62 KB)
Bottom most pixel row
WIN_20210911_20_58_45_Pro.jpg

  View user's profile Send private message
  • Joined: 25 Jul 2007
  • Posts: 716
  • Location: Melbourne, Australia
Reply with quote
Post Posted: Wed Sep 22, 2021 5:20 am
Is there any owners of a VA4 or VA5 varient that may be able to run the test ROM and report whether they get this double image / blur pattern on the LCD?
  View user's profile Send private message
  • Joined: 24 Mar 2021
  • Posts: 120
Reply with quote
Post Posted: Wed Sep 22, 2021 7:24 pm
I apparently have a VA5 Game Gear and I see the same vertical blurring.
  View user's profile Send private message
  • Joined: 25 Jul 2007
  • Posts: 716
  • Location: Melbourne, Australia
Reply with quote
Post Posted: Tue Sep 28, 2021 10:24 am
I missed this somehow, thanks for the feedback.

I've got a couple coming so will be able to verify myself.

The more I've looked into this the more it seems this was intentional and by design. I have a suspicion that this along with the low refresh rate was intended to emulate some of the characteristics of a CRT display.
  View user's profile Send private message
  • Joined: 24 Mar 2021
  • Posts: 120
Reply with quote
Post Posted: Tue Sep 28, 2021 7:47 pm
I forget: Can single vertical pixels show up when in SMS mode? Or when using the TV tuner?

In other words, is this vertical blurring always present - and it might be a hardware defect? Or is there some contexts where it's not present, and it's more likely to be by design here?
  View user's profile Send private message
  • Joined: 25 Jul 2007
  • Posts: 716
  • Location: Melbourne, Australia
Reply with quote
Post Posted: Wed Sep 29, 2021 1:48 am
SMS mode still shows a single pixel by two rows, just like in GG mode, the only difference is that the width is squished down to two sub-pixels.



TV Tuner is harder to verify because the input image gets mangled by Composite Video encoding, also possible scaling if the signal source is higher than PAL/NTSC resolution.

The pixel offset and blur occur in the LCD hardware and are not present in the output from the VDP & SCA chip, so it is likely this affects the TV Tuner also.

That does not necessarily mean it's a hardware defect, consider that VA4/VA5 use a revised LCD design (not sure if still manufactured by Citizen) so they had a chance to correct any defects but evidently chose not to.
smssingle.png (127.53 KB)
smssingle.png

  View user's profile Send private message
Reply to topic



Back to the top of this page

Back to SMS Power!