Would anyone (or, more specifically, Mr. Atkins...) be against putting the gamma correction image (as included in Keith Clark's recent submission) on the main critique page? I usually have my monitor's brightness turned all the way down because I find it easier on my eyes. That setting is not so good for viewing pictures, though, and that little grayscale ramp is very valuable. It would help weed out the "well, I don't like the exposure but it could be my monitor" responses. Objections?

-- Steve Leroux (steve@bigadventures.com), July 30, 1998

Answers

Feel free to steal this bar and use it in your postings. :>

Just in case someone is unfamiliar with the process, dlick the "right" mouse button on the image and then choose "save image as" from the menu that pops up. (This works on a PC with Netscape and MS Internet Exploder).

Happy posting! :>

Keith

-- Keith Clark (ClarkPhotography@spiritone.com), July 30, 1998.

...and for those of using the superior OS :) where only one mouse button is neccessary, simply hold down the mouse button over the image until a popup menu appears, then select "Save this image as...".

-- Gonzalo Castro (gcastro@sybase.com), July 30, 1998.

I've found the gray scale helpful, but from reading links to gamma correction stuff in elsewhere Philip's domain, I'm completely in the dark about what I am supposed to do to make the correction. What I did do was adjust the monitor's brightness and contrast controls to display the whole scale, but that doesn't seem to be what the gamma correction gurus were talking about. Is this more computer geek obscurantist arcana or can a "computer as appliance" cluck like me actually expect to get some benenfit from it?

Frank

-- Frank Kolwicz (bb389@lafn.org), August 01, 1998.

Frank, I'm no expert on this, but the gamma function is a nonlinear mapping of numbers (the values for R, G and B) to physical brightness values (assuming normal settings for the monitor's brightness and contrast). It should be set on the video card. This can be done from the Windows Control Panel/Display dialog, *provided* that your video card supports this function, which unfortunately is a bit rare. A high-end card is more likely to allow this setting than a low-end card. :-)

Ilkka

-- Ilkka Nissild (ilkka.nissila@hut.fi), August 03, 1998.

Thanks, Ilkka,

That's what I thought, based on the reading I did.

Now here goes another wild question - if I set my monitor brightness and contrast to be able to discriminate all the 20 steps in the gray scale, am I in reasonably good shape, considering that I am not trying to match gamma for perfect print output, just to be able to see a decent representation of the posted images.

Frank

-- Frank Kolwicz (bb389@lafn.org), August 03, 1998.

Well I'm posting this very late but maybe some will read it.

The answer is, no, that image won't correct your gamma. You can alter your brightness and contrast to just barely allow you to distingish all shades, so in this case you should be pretty much able to judge what really is burned out or unexposed. But if only your gamma is wrong, black will be black and white will be white but some intermediate shades may be shown lighter or darker on your screen than the other person saw. The further above 1 your gamma value is, the more "compressed" lighter shades are, that is, middlish tones tend to get shown darker.

Annoying, hey? Standards to fix it should be coming "some time soon" :-)

-- Russell Edwards (redwards@mania.physics.swin.edu.au), December 30, 1998.