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Color bar distortion in Illustrator

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Ralph Gould
Color bar distortion in Illustrator
on Apr 27, 2010 at 9:55:28 pm

I am using CS4 to create streams for automated testing of video equipment. When I build color bars in Illustrator and export them in bitmap or .png files to Mazanita software to turn them into
video transport streams, I see curvature in the lines connecting the color bars on the vectorscope. If I export them as bitmap or .png files and play them with Windows Media Player or VLC I see the same distortion The bars are in the vectorscope boxes, but the connecting lines are curved, exhibiting delay. If I import generated bars to Premiere and follow the same process, the vector lines are straight. This leads me to conclude the problem is in Ilustrator. Has anyone else noticed this issue? I realize this is probably not to important in production, but it seems strange. The curvature is worse in HD video than SD video.
Thanks


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les nemeth
Re: Color bar distortion in Illustrator
on Apr 28, 2010 at 7:11:40 am

I believe bitmap files have a certain standard as far as how to write out the bitmap header and the data itself. So I doubt that AI would invent and write its own "standard" - so to speak.

The fact that in some software you see it distorted and in others you don't, leads me to think the opposite. That it's not AI that generates incorrect bitmap data. It's how the software that you are using interprets that data. And maybe some interprets it correctly and some don't.

Just like Internet Exploder 6 was interpreting 24bit transparent PNG files incorrectly. It did not mean that the PNG files were wrong. It was a problem in IE.

If you have Photoshop, create the file there and see what happens. If not, then use the good ol' Paint - which can also create PNG files. See if you get any other results.


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Ralph Gould
Re: Color bar distortion in Illustrator
on Apr 28, 2010 at 6:13:06 pm

I tried creating color bars in Photoshop, then sending the file to Premier. I made an MPEG 2 stream with Encore. The curvature due to delay is still there, but takes place on different vectors. I played the stream with VLC, Windows Media, and after converting the elementary stream to a transport stream, through a hardware decoder. The curvature was there in all three cases. Since it doesn't happen when I capture a frame of video from a Tek HD-SDI video generator and send it to Premiere, it seems it has to be in the way Adobe handles the colors. Does anyone have a way to contact Adobe directly about this to detirmine if this is a know bug?
Thanks


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Vincent Rosati
Re: Color bar distortion in Illustrator
on Apr 28, 2010 at 7:27:38 pm

Any chance you could upload some caps so we can see what you are seeing?

Vince

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Ralph Gould
Re: Color bar distortion in Illustrator
on Apr 28, 2010 at 7:32:37 pm

Vincent,
I have screenshots of my vectorscope I can upload, can I place them on this forum?


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Ralph Gould
Re: Color bar distortion in Illustrator
on Apr 28, 2010 at 8:12:11 pm

Vincent,
Here is a screenshot of my vectorscope looking at the Illustrator bars converted to video by Premier.


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Vincent Rosati
Re: Color bar distortion in Illustrator
on Apr 28, 2010 at 8:21:05 pm

Awesome! Yes. When you respond, under the 'Message:' title there is a small camera icon (and other html formatting/upload icons) that allows you to upload an image, click it.

Vince

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Ralph Gould
Re: Color bar distortion in Illustrator
on Apr 28, 2010 at 8:34:03 pm

Vincent,
I've tried twice to upload the image with the link and neither attempt has shown up. I'm unclear whether I get the link to place in the post from the "embed" or the "link" boxes.


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Vincent Rosati
Re: Color bar distortion in Illustrator
on Apr 28, 2010 at 9:46:42 pm

Hmmm. Maybe make sure the Illustrator file is in RGB color mode, and that the color swatches that you are using are in gamut?? That's about all I can think of. :(

Vince

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Ralph Gould
Re: Color bar distortion in Illustrator
on Apr 28, 2010 at 10:06:43 pm

Vincent,
I am in RGB mode and have tried this with the Adobe 98 color setting and the sRGB color setting. The colors are always in the boxes, but I see the curvature of the vectors connecting the boxes. I wish Adobe had a real tech contact address, I'd just like to know if its a known issue and if there is a way around it. Like I said in the first post, its probably not a problem for most production folks. It does seem strange that Adobe would not correct the problem. I tried posting the issue on their site with screenshots and never had any response. Thanks for your help.


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Vincent Rosati
Re: Color bar distortion in Illustrator
on May 30, 2010 at 7:09:18 pm

Just curious if you've made any progress with this?

I had a thought that.. in Illustrator it takes an extra level of care to make sure that you are working on exact pixel-rows. Maybe some of the color seams are in sub-pixel positions, and when the document is rasterized you're not getting pure colors at the seams.
You could check the objects in the Info palette.

You could check the seams of the rasterized image in Photoshop using the eyedrop tool.
Or, just create the file in Photoshop using the Marquis Tool and the Paint Bucket. Using the Rectangle tool would present the same sub-pixel issues as you would have in Illustrator. ...it this even has anything to do with the issue :)

Vince

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Ralph Gould
Re: Color bar distortion in Illustrator
on Jun 1, 2010 at 12:54:23 pm

Vince,
I used the rectangle tool to build the color bars in Illustrator originally. I then placed the drawing into Premiere, and rendered it as a 30 second clip. I have tried converting it to MPEG2 and MPEG 2 Blue Ray with the same results. The group delay seems to vary between different colors related to the video formats. It will be worse between say red and magenta in 1080I/29.97 than it is in 720P/59.94. I'm stumped at this point. I'd be curious if this was fixed in CS5.
Ralph


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Ralph Gould
Re: Color bar distortion in Illustrator
on Apr 18, 2011 at 9:22:20 pm

I had an engineer from Adobe contact me after I sent the vectorscope screen shots to him in October 2010. He said it is a bug in the way Premiere is handling the file from Illustrator. I spoke with him last week. They were supposed to fix in CS 5.5, but the fix has been put off until another version. The group delay will be in all images created in Illustrator and placed in Premier. Probably not an issue with most production work, but it should be fixed.


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