?: why are graphics on PC darker than Mac?

?: why are graphics on PC darker than Mac?

Post by ratt » Fri, 27 Dec 1996 04:00:00



I think the dark/light, Mac/PC issue is related to gamma correction. I
use Boxtop PhotoGIF, ProJPG utilities which allow you to change the
gamma settings in you GIF files. It makes smaller files as well as some
other handy features.

http://www.boxtopsoft.com/

Good Luck
--ratta


> I recently put some scanned photos on my wife's web page
>  (www.welch.jhu.edu/~barouch), and they looked fine on our Mac,
>  but were far too dark on the hospital's PCs (Netscape 3 in WinNT
>  client).  This morning I lightened them and re-uploaded, but
>  I suspect they're still too dark.  Why?

> BTW, I used a Umax T630, then converted PICT to JPEG using Clip2Gif.

> Also, I like to use little grayscale text images as backgrounds
>  (see also www.gl.umbc.edu/~fuy1/comics), and I've found that
>  gray shades vary WIDELY in different OS'es -- Win3.1, Win95, and
>  WinNT all look different, and X Windows is even farther.  Is there
>  a Mac utility that will help me make more platform-friendly grays?

> -F
> .

 
 
 

?: why are graphics on PC darker than Mac?

Post by Thomas Weig » Fri, 27 Dec 1996 04:00:00



> I think the dark/light, Mac/PC issue is related to gamma correction. I
> use Boxtop PhotoGIF, ProJPG utilities which allow you to change the
> gamma settings in you GIF files. It makes smaller files as well as some
> other handy features.

Yup, it's the gamma correction. I *believe* that you can check the final
results by switching from gamma correction 1.8 to uncorrected (or
non-corrected or whatever it says on American systems). This is much closer
to PC settings than the original Mac settings. Of course, this requires
that you have a Mac, a system and a screen that supports different gamma
corrections. Not all do, if I'm not mistaken (eg, I recall not being able
to check this properly while on an old 68* Mac with a system older than
7.5.2).

And, yes, PhotoGIF is the best GIF tool available. ProJPEG allows you to
create progressive JPEG files, right? That's the best choice for JPEGs.
They become appr. 30 % smaller. Only con is that browsers prior to 2.*
cannot view them (of course, according to the latest stats, only 1.1 % use
Netscape 1.*).

Quote:> > Also, I like to use little grayscale text images as backgrounds
> >  (see also www.gl.umbc.edu/~fuy1/comics), and I've found that
> >  gray shades vary WIDELY in different OS'es -- Win3.1, Win95, and
> >  WinNT all look different, and X Windows is even farther.  Is there
> >  a Mac utility that will help me make more platform-friendly grays?

In Photoshop, convert them to indexed colors, then set large areas of grays
to browser safe colors (browser safe grays are (following RGB) 51,51,51;
102,102,102; 153,153,153; 204,204,204; as well as black and white (for
obvious reasons). Then convert them to RGB again, and the images should
behave correctly and can be saved as JPEGs. Naturally you could skip this
last step. Text looks better as GIFs and a 3-bit GIFs should be sufficient
for this task.

//thomas

+-----------------------------------------------------+


   \ Toto, I have feeling we're not in Kansas anymore |
    +-------------------------------------------------+

 
 
 

?: why are graphics on PC darker than Mac?

Post by Francis A » Sun, 29 Dec 1996 04:00:00




>Yup, it's the gamma correction. I *believe* that you can check the final

Thanks for reminding me about gamma.  I've switched to uncorrected,
 and will make appropriate adjustments to the pictures.

I've also downloaded ProJPEG & PhotoGIF, thanks for the pointers.

Quote:>to browser safe colors (browser safe grays are (following RGB) 51,51,51;
>102,102,102; 153,153,153; 204,204,204; as well as black and white (for

Thanks again.

-F
.

 
 
 

?: why are graphics on PC darker than Mac?

Post by Thomas Weig » Sun, 05 Jan 1997 04:00:00



> I think the dark/light, Mac/PC issue is related to gamma correction. I
> use Boxtop PhotoGIF, ProJPG utilities which allow you to change the
> gamma settings in you GIF files. It makes smaller files as well as some
> other handy features.

Just for the sake of it ...

First of all, I hope everybody is aware of the fact that the GIF89a Export
filter available for Photoshop create files that crashes Netscape 3.* on
Macs. This usually only occurs when large files are involved. Meaning that
smaller images are handled correctly most of the time. Only tests can tell
for sure though.

Second, just today I found out that there are some very important
differences in file size between the PhotoGIF and the GIF89a Export filters
for Mac. Ended up testing three images using these two filters:

1x1 pixel, 1-bit  transparent gif (commonly known as dot_clear.gif or similar).
PhotoGIF file size 584 byte ; GIF89a Export file size 40 byte

25x2000, 4-bit (12 colors) background image, mostly yellow transparent
background but also including a blue section and a drop shadow.
PhotoGIF file size 1570 byte ; GIF89a Export file size 505 byte

600x400, 8-bit multi-element image, no transparency (as a Photoshop file it
takes up appr. 600k).
PhotoGIF file size 32990 byte ; GIF89a Export file size 32395 byte

While this doesn't say anything about how they will expand on different
systems, it sure sheds some light on the importance of using the exactly
correct tool for the job. Merely *one* GIF filter may not be enough.

Test, btw, done with custom logo etc turned off.

Thought someone might find it interesting ...

//thomas

+-----------------------------------------------------+


   \ Toto, I have feeling we're not in Kansas anymore |
    +-------------------------------------------------+

 
 
 

?: why are graphics on PC darker than Mac?

Post by Pain » Tue, 07 Jan 1997 04:00:00



> I recently put some scanned photos on my wife's web page
>  (www.welch.jhu.edu/~barouch), and they looked fine on our Mac,
>  but were far too dark on the hospital's PCs (Netscape 3 in WinNT
>  client).  This morning I lightened them and re-uploaded, but
>  I suspect they're still too dark.  Why?

I recently came across an couple of lines in an electronic design
newsletter which said that PC and UNIX machines tend to display colours
much darker than Macs, and that when designing graphics for a Web site,
you can tell how they'll look on other platforms by adjusting Gamma.
Open your Gamma control panel and set the Target Gamma to 2.2.  If you
have Photoshop, Gamma is in the Calibration folder of the Goodies folder
in your Photoshop folder.  If you have PageMaker, it is in the Utilities
folder of the PageMaker folder.

Hope this may be useful, if not, have a nice day anyway.
Wendy.