Monitor Gamma and Picture Gamma

Monitor Gamma and Picture Gamma

Post by ot.. » Sat, 21 Aug 1999 04:00:00



There has been much discussion about Gamma on this list lately, a
topic of some confusion because there is Monitor Gamma and Picture
Gamma, and the two are not the same.

Theoretically, a perfect monitor could be built, where pure red shows
as pure red, pure green as pure green, etc.; however, because the
components that are used to build electronic equipment are highly
inaccurate, a perfect monitor is only theoretical.

The actual values of resistors, capacitors, and coils that go into a
piece of electronics vary greatly from their stated values. For
example, a higher-grade 3,000 ohm resistor can vary in value from
2,850 to 3,150 ohms. Standard resistors have a 10% tolerance. The
value of a capacitor can vary from +50% to -20% of its rated value.
Then there are factors such as stray capacitance, wire resistiance,
and inductance caused by the current to contend with.

So, while the design engineer says this circuit will do this, the
resultant application of that design might not, and they add variable
components to allow "tweaking". Instead of having a 3,000 ohm resistor
in some part of the circuit, they might use a 2,500 ohm one along with
an adjustable 250 to 750 ohm one.

The whole point of this is that your monitor is not going to be
perfect, even when it is new, and as it ages, the values of its
components (especially capacitors) will change.

Adjusting your monitor gamma is a way of tweaking it so pure red show
as pure red, etc. It also is used to establish a uniform grayscale.
This can be done completely independently of your graphics program,
and needs to be repeated periodically to compensate to component
aging.

On the other hand, if you use a program like Paint Shop Pro to adjust
the gamma value of a picture, you actually change the palette values
of that picture. One way to see this is to compare the palettes of a
picture at different gamma value adjustments (double-click on the
foreground or background color box or actually open the Jasc-format
palettes in a text editor).

Calibrating the gamma of your monitor just changes the way you view
pictures, not someone else's view. It's becoming the norm for PC
monitors to include gamma adjustment (I believe that it has been built
into Macs for some time, and UNIX). A good package will allow you to
set the values for red, green, and blue independently, along with
grayscale. If your monitor does not include this capability, then I
would search out one of the web sites that have been set up to handle
this, and not foing it from within a paint program.

I have found that I get a good match between my scanner, my printer,
and my monitor since I did the calibration.

Adjusting the gamma value of a picture can be useful for "tweaking"
its appearance, but remember that you are actually changing the colors
when you do so.

co

------------------------------------------------
NOTE: any e-mail sent to the originating address
is automatically deleted without being read.
------------------------------------------------

 
 
 

Monitor Gamma and Picture Gamma

Post by Chuck Anderso » Sat, 21 Aug 1999 04:00:00



> There has been much discussion about Gamma on this list lately, a
> topic of some confusion because there is Monitor Gamma and Picture
> Gamma, and the two are not the same.

> Theoretically, a perfect monitor could be built, where pure red shows
> as pure red, pure green as pure green, etc.; however, because the
> components that are used to build electronic equipment are highly
> inaccurate, a perfect monitor is only theoretical.

> The actual values of resistors, capacitors, and coils that go into a
> piece of electronics vary greatly from their stated values. For
> example, a higher-grade 3,000 ohm resistor can vary in value from
> 2,850 to 3,150 ohms. Standard resistors have a 10% tolerance. The
> value of a capacitor can vary from +50% to -20% of its rated value.
> Then there are factors such as stray capacitance, wire resistiance,
> and inductance caused by the current to contend with.

> So, while the design engineer says this circuit will do this, the
> resultant application of that design might not, and they add variable
> components to allow "tweaking". Instead of having a 3,000 ohm resistor
> in some part of the circuit, they might use a 2,500 ohm one along with
> an adjustable 250 to 750 ohm one.

> The whole point of this is that your monitor is not going to be
> perfect, even when it is new, and as it ages, the values of its
> components (especially capacitors) will change.

> Adjusting your monitor gamma is a way of tweaking it so pure red show
> as pure red, etc. It also is used to establish a uniform grayscale.
> This can be done completely independently of your graphics program,
> and needs to be repeated periodically to compensate to component
> aging.

> On the other hand, if you use a program like Paint Shop Pro to adjust
> the gamma value of a picture, you actually change the palette values
> of that picture. One way to see this is to compare the palettes of a
> picture at different gamma value adjustments (double-click on the
> foreground or background color box or actually open the Jasc-format
> palettes in a text editor).

> Calibrating the gamma of your monitor just changes the way you view
> pictures, not someone else's view. It's becoming the norm for PC
> monitors to include gamma adjustment (I believe that it has been built
> into Macs for some time, and UNIX). A good package will allow you to
> set the values for red, green, and blue independently, along with
> grayscale. If your monitor does not include this capability, then I
> would search out one of the web sites that have been set up to handle
> this, and not foing it from within a paint program.

> I have found that I get a good match between my scanner, my printer,
> and my monitor since I did the calibration.

> Adjusting the gamma value of a picture can be useful for "tweaking"
> its appearance, but remember that you are actually changing the colors
> when you do so.

> co

> ------------------------------------------------
> NOTE: any e-mail sent to the originating address
> is automatically deleted without being read.
> ------------------------------------------------

I assume the calibration you are using is not the simple bars that PSP
uses.  If I set my monitor gamma according to those instructions, pictures
that look fine to me (on the monitor), end up far too bright on others'
monitors, because of the compensation I've done at my end.

 ********************************************************************
 Chuck Anderson    chuck-anderso-at-earthlink-dot-net (remove dashes)
 Boulder, CO       http://home.earthlink.net/~chuckanderso
 Tolerance is recognizing that other people have different ideals
 and needs than you. Compromise is acting on that knowledge.
 *****************************************************

 
 
 

Monitor Gamma and Picture Gamma

Post by JoFl » Mon, 23 Aug 1999 04:00:00


I've been reading these threads, but I still can't figure out something.
Maybe, Chuck, you've brought up something having to do with my problem.
Using the monitor gamma correction bars within PSP adjusts the brightness I
see in the pics open in PSP, but does not effect images from the web or
newsgroups.  Is there a Windows gamma correction?  Everything I see on the
newsgroups is much darker than what everyone else sees.  However, with my
gamma corrected in PSP, when I do a screen capture or cut and paste or
whatever into PSP from the newsgroups, I can then see the dark images fine.
So...how can I adjust the gamma for the stuff I see on the newsgroups/web?

--
JoFlo
Paint Shop ProPourri
http://members.xoom.com/JoFlo/psp/psp.htm

"We are not human beings on a spiritual journey, but spiritual beings on a
human journey." - Stephen R. Covey



>> There has been much discussion about Gamma on this list lately, a
>> topic of some confusion because there is Monitor Gamma and Picture
>> Gamma, and the two are not the same.

>> Theoretically, a perfect monitor could be built, where pure red shows
>> as pure red, pure green as pure green, etc.; however, because the
>> components that are used to build electronic equipment are highly
>> inaccurate, a perfect monitor is only theoretical.

>> The actual values of resistors, capacitors, and coils that go into a
>> piece of electronics vary greatly from their stated values. For
>> example, a higher-grade 3,000 ohm resistor can vary in value from
>> 2,850 to 3,150 ohms. Standard resistors have a 10% tolerance. The
>> value of a capacitor can vary from +50% to -20% of its rated value.
>> Then there are factors such as stray capacitance, wire resistiance,
>> and inductance caused by the current to contend with.

>> So, while the design engineer says this circuit will do this, the
>> resultant application of that design might not, and they add variable
>> components to allow "tweaking". Instead of having a 3,000 ohm resistor
>> in some part of the circuit, they might use a 2,500 ohm one along with
>> an adjustable 250 to 750 ohm one.

>> The whole point of this is that your monitor is not going to be
>> perfect, even when it is new, and as it ages, the values of its
>> components (especially capacitors) will change.

>> Adjusting your monitor gamma is a way of tweaking it so pure red show
>> as pure red, etc. It also is used to establish a uniform grayscale.
>> This can be done completely independently of your graphics program,
>> and needs to be repeated periodically to compensate to component
>> aging.

>> On the other hand, if you use a program like Paint Shop Pro to adjust
>> the gamma value of a picture, you actually change the palette values
>> of that picture. One way to see this is to compare the palettes of a
>> picture at different gamma value adjustments (double-click on the
>> foreground or background color box or actually open the Jasc-format
>> palettes in a text editor).

>> Calibrating the gamma of your monitor just changes the way you view
>> pictures, not someone else's view. It's becoming the norm for PC
>> monitors to include gamma adjustment (I believe that it has been built
>> into Macs for some time, and UNIX). A good package will allow you to
>> set the values for red, green, and blue independently, along with
>> grayscale. If your monitor does not include this capability, then I
>> would search out one of the web sites that have been set up to handle
>> this, and not foing it from within a paint program.

>> I have found that I get a good match between my scanner, my printer,
>> and my monitor since I did the calibration.

>> Adjusting the gamma value of a picture can be useful for "tweaking"
>> its appearance, but remember that you are actually changing the colors
>> when you do so.

>> co

>> ------------------------------------------------
>> NOTE: any e-mail sent to the originating address
>> is automatically deleted without being read.
>> ------------------------------------------------

>I assume the calibration you are using is not the simple bars that PSP
>uses.  If I set my monitor gamma according to those instructions, pictures
>that look fine to me (on the monitor), end up far too bright on others'
>monitors, because of the compensation I've done at my end.

> ********************************************************************
> Chuck Anderson    chuck-anderso-at-earthlink-dot-net (remove dashes)
> Boulder, CO       http://home.earthlink.net/~chuckanderso
> Tolerance is recognizing that other people have different ideals
> and needs than you. Compromise is acting on that knowledge.
> *****************************************************

 
 
 

Monitor Gamma and Picture Gamma

Post by ot.. » Tue, 24 Aug 1999 04:00:00


On Fri, 20 Aug 1999 12:03:57 -0600, Chuck Anderson


>I assume the calibration you are using is not the simple bars that PSP
>uses.  If I set my monitor gamma according to those instructions, pictures
>that look fine to me (on the monitor), end up far too bright on others'
>monitors, because of the compensation I've done at my end.

With my previous monitor, I used a gamma correction site I found on
the web, but this monitor came with it's own routine.

There are some good links on this page about gamma correction,
especially "Making Good Cross Platform And WWW Pictures" and "Reducing
Eyestrain from Video and Computer Monitors."

http://www.cgsd.com/papers/gamma.html

Most people get a system, turn their monitor on, and accept however it
is set. If they would just set the Black Level properly, it would
help.

Personally, I have my system set so I view things properly, but most
things I see on the web look okay, too. My feeling is that if people
don't want to try and adjust their monitor properly, then they see
whatever they see.

BTW, it is a lot easier doing this with the more expensive PC monitors
thatn with most of the less expensive ones. Bit it's still a pain in
the you=know-where.

co
------------------------------------------------
NOTE: any e-mail sent to the originating address
is automatically deleted without being read.
------------------------------------------------

 
 
 

Monitor Gamma and Picture Gamma

Post by Chuck Anderso » Tue, 24 Aug 1999 04:00:00


Now that I think about it.  I ran just such a program on my system shortly
after I got it, a couple of years ago.  It's called the Nokia monitor test and
it help you adjust all of your monitor parameters properly (I don't have any
color controls so I probably can't change monitor gamma.)

It is freeware, a 1.4MB zip file.  You could search for it.

It helps you adjust black cut-off, white, focus, convergence, geometry, colors,
. . .   The help file is very useful and explains a lot.

If need be, I'll mail it to you.


> I've been reading these threads, but I still can't figure out something.
> Maybe, Chuck, you've brought up something having to do with my problem.
> Using the monitor gamma correction bars within PSP adjusts the brightness I
> see in the pics open in PSP, but does not effect images from the web or
> newsgroups.  Is there a Windows gamma correction?  Everything I see on the
> newsgroups is much darker than what everyone else sees.  However, with my
> gamma corrected in PSP, when I do a screen capture or cut and paste or
> whatever into PSP from the newsgroups, I can then see the dark images fine.
> So...how can I adjust the gamma for the stuff I see on the newsgroups/web?

> --
> JoFlo
> Paint Shop ProPourri
> http://members.xoom.com/JoFlo/psp/psp.htm

> "We are not human beings on a spiritual journey, but spiritual beings on a
> human journey." - Stephen R. Covey



> >> There has been much discussion about Gamma on this list lately, a
> >> topic of some confusion because there is Monitor Gamma and Picture
> >> Gamma, and the two are not the same.

> >> Theoretically, a perfect monitor could be built, where pure red shows
> >> as pure red, pure green as pure green, etc.; however, because the
> >> components that are used to build electronic equipment are highly
> >> inaccurate, a perfect monitor is only theoretical.

> >> The actual values of resistors, capacitors, and coils that go into a
> >> piece of electronics vary greatly from their stated values. For
> >> example, a higher-grade 3,000 ohm resistor can vary in value from
> >> 2,850 to 3,150 ohms. Standard resistors have a 10% tolerance. The
> >> value of a capacitor can vary from +50% to -20% of its rated value.
> >> Then there are factors such as stray capacitance, wire resistiance,
> >> and inductance caused by the current to contend with.

> >> So, while the design engineer says this circuit will do this, the
> >> resultant application of that design might not, and they add variable
> >> components to allow "tweaking". Instead of having a 3,000 ohm resistor
> >> in some part of the circuit, they might use a 2,500 ohm one along with
> >> an adjustable 250 to 750 ohm one.

> >> The whole point of this is that your monitor is not going to be
> >> perfect, even when it is new, and as it ages, the values of its
> >> components (especially capacitors) will change.

> >> Adjusting your monitor gamma is a way of tweaking it so pure red show
> >> as pure red, etc. It also is used to establish a uniform grayscale.
> >> This can be done completely independently of your graphics program,
> >> and needs to be repeated periodically to compensate to component
> >> aging.

> >> On the other hand, if you use a program like Paint Shop Pro to adjust
> >> the gamma value of a picture, you actually change the palette values
> >> of that picture. One way to see this is to compare the palettes of a
> >> picture at different gamma value adjustments (double-click on the
> >> foreground or background color box or actually open the Jasc-format
> >> palettes in a text editor).

> >> Calibrating the gamma of your monitor just changes the way you view
> >> pictures, not someone else's view. It's becoming the norm for PC
> >> monitors to include gamma adjustment (I believe that it has been built
> >> into Macs for some time, and UNIX). A good package will allow you to
> >> set the values for red, green, and blue independently, along with
> >> grayscale. If your monitor does not include this capability, then I
> >> would search out one of the web sites that have been set up to handle
> >> this, and not foing it from within a paint program.

> >> I have found that I get a good match between my scanner, my printer,
> >> and my monitor since I did the calibration.

> >> Adjusting the gamma value of a picture can be useful for "tweaking"
> >> its appearance, but remember that you are actually changing the colors
> >> when you do so.

> >> co

> >> ------------------------------------------------
> >> NOTE: any e-mail sent to the originating address
> >> is automatically deleted without being read.
> >> ------------------------------------------------

> >I assume the calibration you are using is not the simple bars that PSP
> >uses.  If I set my monitor gamma according to those instructions, pictures
> >that look fine to me (on the monitor), end up far too bright on others'
> >monitors, because of the compensation I've done at my end.

> > ********************************************************************
> > Chuck Anderson    chuck-anderso-at-earthlink-dot-net (remove dashes)
> > Boulder, CO       http://home.earthlink.net/~chuckanderso
> > Tolerance is recognizing that other people have different ideals
> > and needs than you. Compromise is acting on that knowledge.
> > *****************************************************

--
 ********************************************************************
 Chuck Anderson    chuck-anderso-at-earthlink-dot-net (remove dashes)
 Boulder, CO       http://home.earthlink.net/~chuckanderso
 Tolerance is recognizing that other people have different ideals
 and needs than you. Compromise is acting on that knowledge.
 *****************************************************
 
 
 

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Emailing Me? Lose the "Z" in my address. You'll be glad you did.Thanks.

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