Interlaced colors - please test & take a photo!

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aeb
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Interlaced colors - please test & take a photo!

Post by aeb »

Have any of you played around with interlaced colors?

Here's a quick test code which alternates between two duplicate screens and two color RAM's every raster line. The fields are then swapped once every frame.

I'm curious about what this looks on different video systems, PAL, NTSC, old color tv's, modern LCD displays, whatever you may be using. I recall the VIC 20 colors thru TV adaptor are very mushy, especially red and green.

Please post a photo of your VIC 20 display if you try it!

Ideally, if the fields blend perfectly, it should look something like this:
Image

There's a lot more color combinations to try and some of them obviously work better than others. Colors with the same or almost the same intensity level should blend well.

Download the files here: http://we.tl/Xuk18atBs6

Or type-in this (unexpanded PAL VIC):

10 printchr$(147);:z=37888:d=832
11 fora=1to22:readb,c,a$:printchr$(18)" "chr$(146)a$
12 forx=0to21:pokez+x,b:pokez+512+x,c:next:z=z+22:next
13 fora=0to511:poke7168+a,peek(7680+a):next
14 reada:ifa>-1thenpoked,a:d=d+1:goto14
15 poke36879,8:sys832
101 data1,1,"white"
102 data2,2,"red"
103 data3,3,"cyan"
104 data4,4,"purple"
105 data5,5,"green"
106 data6,6,"blue"
107 data7,7,"yellow"
108 data0,6,"dark blue"
109 data0,2,"dark red"
110 data6,2,"dark purple"
111 data2,5,"brown (red-green)"
112 data6,5,"sea blue (blue-gr.)"
113 data2,4,"purple-red"
114 data6,4,"purple-blue"
115 data4,5,"gray (purple-gr.)"
116 data3,6,"light blue"
117 data3,1,"light cyan"
118 data4,1,"light purple"
119 data7,1,"light yellow"
120 data3,5,"lime (green-cyan)"
121 data5,1,"light green"
122 data2,1,"pink (red-white)"
200 data120,162,38,169,150,236,4,144,208,251,141,2,144,73,128,160,11,136,208,253,234
201 data234,232,208,241,173,68,3,73,128,141,68,3,208,222,-1


For NTSC replace the last two lines with:

200 data120,162,24,169,150,236,4,144,208,251,234,234,234,234,234,73,128,160,9,234,234
201 data234,141,2,144,136,208,253,232,224,211,208,238,173,68,3,73,128,141,68,3,208,214
202 data-1
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Mike
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Re: Interlaced colors - please test & take a photo!

Post by Mike »

Hi, Aleksi,
aeb wrote:Have any of you played around with interlaced colors?
Some time ago, I did a routine which blended the three global colour registers both between adjacent frames and adjacent lines. It was mainly used to achieve two intermediate grey levels between black and white: 'VIC 20 in Black and White mode'.

On the NTSC VIC-20, tokra and I implemented a true interlaced graphics mode, which also switched between two different colour RAMs on two fields (with single height characters): MIFLI, demoed in VIC can again. For the resulting 4x16 pixels attribute cells with multi-colour characters, the image converter took the mixing colours into consideration.
Please post a photo of your VIC 20 display if you try it!
I'll be able to do it next week. That'll be on a 1084, with a VIC-20 that has the S-Video mod built-in. It will be tricky though to get this right, as one needs an exposure time of at least 1/25th second to fully blend two adjacent frames.

Greetings,

Michael
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Witzo
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Post by Witzo »

Cool trick Aeb!

And almost impossible to photograph.
Here are some tries, unedited except for resizing to fit on the forum screen.
PAL VIC on a CRT using RF modulator.
(Shaking the RF modulator always changes my colours a bit, these were taken with the start screen background white as off-white, not bright-white.).

With flash.
Image

Without flash, exposes longer hence shaking hands effect, and bright colours turn white with over-exposure.
Image

From a distance with flash (without flash was too shaken).
Image
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tokra
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Post by tokra »

Nice idea. My PAL-VIC is S-Video modded, my NTSC-VIC is not. I have a 1901 and a 1084-monitor. You can find the pictures here:

http://www.tokra.de/vic/lacepal1901.jpg
http://www.tokra.de/vic/lacepal1084.jpg
http://www.tokra.de/vic/lacentsc1084.jpg

I agree it's hard to photograph. The NTSC-blending looked more stable than PAL. Probably due to 30 Hz > 25 Hz.
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Kweepa
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Post by Kweepa »

Yay! Aleksi returns to the VIC!
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Mike
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Post by Mike »

tokra wrote:I agree it's hard to photograph.
A tripod and a good choice of aperture are your best friends here. ;)

In the meantime, here's this program as an alternative to produce all 28 mixing 'colours' in a systematic way using a checkerboard pattern: (download)

Code: Select all

10 POKE55,0:POKE56,28:CLR:V=36864
11 POKEV+0,PEEK(60900)+6
12 POKEV+1,PEEK(60901)-2
13 POKEV+2,128+16
14 POKEV+3,48
15 POKEV+15,8
16 FORT=673TO696:READA:POKET,A:NEXT
17 FORT=0TO383:POKE7168+T,160:POKE7680+T,160:NEXT
18 FORX=0TO7:FORY=0TO7
19 FORX2=0TO1:FORY2=0TO2
20 POKE37888+48*Y+16*Y2+2*X+X2,X
21 POKE38400+48*Y+16*Y2+2*X+X2,Y
22 NEXT:NEXT:NEXT:NEXT
23 SYS673
24 :
25 DATA 120,162,0,236,4,144,208,251,56,169,160,237
26 DATA 2,144,141,2,144,236,4,144,240,251,208,235
It works on both PAL and NTSC.
Last edited by Mike on Thu Feb 20, 2014 5:46 pm, edited 1 time in total.
lordbubsy
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Post by lordbubsy »

I photographed both aeb’s and Mike’s versions with several exposure times. Out of 24 pictures those 5 were best:
Photo 4 matches the original most, except for the heavy flickering.

Tested on:
VIC-20 NTSC two prong
ASSY NO. 324003
1981 COMMODORE INTL
KU-14194HB
FAB NO. 324002-01 REV. F

Sony Trinitron - KV-21CL10 21 inch color tv

Photo 1: 1/30 (sec)
Photo 2: 1/40 (sec)
Photo 3: 1/40 (sec)
Photo 4: 1/10 (sec) white balance fluorescent
Photo 5: 1/20 (sec) white balance light bulb

If the photos are too big, I can reduce them to a given width...
Edit: replaced with thumbs and dl to the originals.

Image
http://content.wuala.com/contents/lordb ... 1.jpg?dl=1
Image
http://content.wuala.com/contents/lordb ... 2.jpg?dl=1
Image
http://content.wuala.com/contents/lordb ... 3.jpg?dl=1
Image
http://content.wuala.com/contents/lordb ... 4.jpg?dl=1
Image
http://content.wuala.com/contents/lordb ... 5.jpg?dl=1
Last edited by lordbubsy on Sun Jan 06, 2013 4:57 am, edited 3 times in total.
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Kananga
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Post by Kananga »

A few weeks ago I tried mixing all background colors (horizontal bars) with all foreground colors (vertical bars) by displaying the vertical bars on every second frame:
Image
Unfortunately, it only looks good on the picture, because it flickers horribly.
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Mike
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Post by Mike »

lordbubsy wrote:If the photos are too big, i can reduce them to a given width ...
You could replace them with thumbnails+links to the originals, as they make the text in this thread hard to read.
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Jeff-20
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Post by Jeff-20 »

It's a rare occasion when I wish I could see color, but I have in the past expressed interest in producing gray scales. I wonder how many grays could be made.
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aeb
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Post by aeb »

Thanks for all the photos. How bad is the flicker? Would that be usable in a 'board game' or such? I'm most interested in the colors combining green with some other color. But light blue would be also nice.

And then another thing to try out: What about if you stop switching between the fields every frame? See DATA line 201 and change the value of 128 to 0. Now it produces a static screen, similar to the the first image below.

Does that produce a blended color on any TV/monitor or can you see the one-pixel vertical stripes on every combination?

Image

Image
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