Scrapbook - Gamma Correction Tutorial
(by Tobias, Mar 7, 2006)
This is just a little tutorial I thought could be helpful for quite a few, giving a short introduction about how to change the gamma level of a picture. You'll very likely be able to find similar or identical functionality in your favourite imaging and drawing software, so have a look at your software's manual. I'll explain how to change the gamma level with IrfanView, which is an excellent imaging software that is all free, so if you're unsure how to do it with your program, or in case your program can't do it, give IrfanView a try, it's perfect for those little changes on pictures.
Why Gamma Correction?Anyhow, if you ever scanned pictures, especially with coloured pencils, or pencil in general, you might have noticed that your pictures are really bright, and the colours are rather faint, compared to what it looks like on the paper you scanned. What do you do? There are a few things you might think of - the most obvious one is to lower the brightness of the picture, however this has the unfortunate effect that the picture in whole will get darker - so the white paper before might be grey afterwards, which isn't quite what you'd want. Raising the contrast isn't that good either, it'd make the bold colours bolder and the faint colours fainter. And raising the intensity of a picture whitens out the colours and makes them look overdone, while lowering it will make the picture become all grey-ish.One powerful feature that often gets overlooked is the Gamma Correction. It basically makes the colours darker and bolder, without affecting the bright sections of the image - so the white background will stay perfectly white, and faint spots that can barely be seen won't become a lot darker either.
How to use Gamma Correction on your workHow do you use it? If you don't have Gamma Correction with your software, and if you haven't done so already, download IrfanView. Of course, if your favourite program can already do that, feel free to use that one instead (for Photoshop, look in the Image / Adjustments menu and click "Levels") ^-^ Once you got Irfanview running, click "File" and "Open" to open your work (alternatively you can also click "File" and "Acquire / Batch Scanning" to scan your picture). The Gamma Correction you can find in the "Image" menu, in a menu entry named "Enhance Colors". You'll be given quite a few options to change, but the one you want to use is the "Gamma Correction". If you leave it at "1.00", nothing will be changed. By decreasing the value, you'll make the picture darker and the colours bolder, by increasing it you'll achieve the opposite effect: the picture will become brighter and the colours fainter. Here you really have to try out how much you need to darken your work so the colours look good - I usually use something between 0.75 and 0.50. If you click "OK" and you're not satisfied, you can just click "Edit" and "Undo" to restore the original picture and try again, with a higher value of it was too dark, or a lower value if it was too bright.(Usually once you found the best value for your drawing, it'll probably always be roughly the same, since your pencils and your scanner will always be as bright as they're now).
ConclusionIrfanview is also very good when it comes to resizing your work, so in case your usual program doesn't do too well on it, you can just use the "Resize/Resample" feature found in the "Image" menu. For drawings, a convenient size is if they fit into a 800x800 pixels box, but if there's a lot of fine details to spot, you could also use a larger size. Remember, experimenting really helps here, and you can always undo what you did, so no worries here ^-^Anyhow, that concludes my little tutorial, I hope it was of help, and if you have any questions, just ask, I'll try my best to help you out ^-^