Dr. Steve wrote:
>
> Here's a question that's been bothering me for a while: if I create a
> nice-looking .gif graphic that displays well in MSIE 4.0, why does it seem
> "blotchy" in NS 3.0 Gold?
>
> For example, see http://log.on.ca/briggs/1.html and the b&w picture of the
> retired optometrist.(<img src="vickersbig.gif" width=332
> height=385 border=0
> alt=" ">).
>
> You can also see a bit of this on David Essig's web site, which I've been
> working on lately: http://www.island.net/~essig
>
> Any ideas on this - is it only applicable to b&w images - and how
> do I avoid
> it?
No, it doesn't apply only to b&w images.
Your images looked the same on my PC NT 16bit system in NS 3 and MSIE 4, but
here's some thoughts:
I downloaded map.gif from http://www.island.net/~essig/ and opened it in
Photoshop. You have the image saved at 216 colors. For starters, I would try
reducing the amount of colors used in that image. It would make sense for
you to want to keep it a gif, even though it's a photographic image, since
it shares so much solid black space with the background of your page. You
will have to sacrifice image quality to keep the black black. If you are
more concerned about max image quality, save it as a jpg from the original
16-24 bit image. However, if you use compression on your jpg (such as 80%),
then you run the risk of unpredictable dithering in the solid black area -
and thus an unpredictable mesh with your background.
I also suggest, if you decide to go gif with the map image, that you make
sure that the text colors overlaid in the image are browser safe colors. It
will reduce the dithering (I didn't examine it to see if you already used
b-safe colors). Also, make sure that the black area is truly black, and not
some minor variation. In Photoshop you can open the "info" window and pass
the eye dropper over the black area, then watch the info to see if the black
stays 0 0 0 (RGB).
I've found that using an adaptive palette for gif images and saving them in
as low a color depth as possible (still looking good) will make the palette
demands on 256 color systems cause less random dithering. I try to stay
under 216 colors total as a sum for all gifs on a page. If you know what
images will be used together on the page, you can use something like
Debabalizer to create an optimized palette for the image collection. Since
your map will be used on different pages, that's not really an option.
As Kathy pointed out: A rule of thumb is photos=jpg, flat colors=gif. That
is because of the way the images are saved. Jpg loses color data and dithers
to make up for it. Gif doesn't. It gets trickier when you want to preserve a
flat color (black in this case) in a photo image.
Another workaround is to cut your map into pieces and use jpg for the photo
parts and gif for the solid parts. You'll have to experiment with this,
because your image won't necessarily cut up into nice neat rectangles
according to the shape in the image: you may get some unpredictable edges
between the jpgs and gifs.
Suz went into depth on Image Ready and the ways it lets you tweak palettes.
She got some very good results with gifs. You may want to check her post
earlier this week.
Another thing I noticed in your site:
http://www.island.net/~essig/recordings.html
Is that you used a combination of jpgs and gifs for your album cover images.
I think you would have had better results if you went all jpg and let the
browser straighten out the colors. Your jpgs and gifs will 'rob' each other
of colors on 256 systems. I've found that using jpgs for bulky colored
images leads to better results when viewing at 256 and great results at
16-24bit. If you use gifs, your images will not look better at 16-24 bit,
they'll be the same old lumpy gifs they are at 256 (except that one jpg,
which will look much better than the gifs).
As is, your album covers have pseudo-solid colors that are dithered. I don't
know if they started out dithered or were actually solid colors, but since
they dither against each other as gifs, you might as well let them dither as
jpgs. Then at least 16-24bit viewers will see better images.
Regarding your initial question: I don't see any difference in NS4, 3 or
MSIE 4. Your gifs look the same in each. If you are on a PC and are
test-viewing your pages by "quick-switching" to 256 color mode from 16 bit,
I've found that browsers don't always deal with the change very well: you
may have to restart in 256 to get the palettes to work as they would for
users starting in 256. Or it may just be my buggy vid card.
I also read somewhere that NS 4 uses a different browser safe palette than
NS 3, but haven't seen any differences in my sites. It could be malarky.
Anyone know?
Jack
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