Image magick (or other) program - grey bgnd to white ?

[tkr]

Hello Everyone,

I use the custom white balance setting on my camera (A480) with a white sheet of paper to set the white balance before I start shooting pics.
However when I view the images later on, the white background of the pages appears to be greyish. Actually now that I look at it, the un-cropped image seems to have a whiter background than the cropped image.

a) Is my lighting not good enough ? (as you can see I'm using only one bulb)
b) Can I use image magick, Gimp or some other program to convert the grey background into white ?


Thanks
TKR

[Heelgrasper]

Have you tried setting the EV at +1 or +2?

[tkr]

Tks for the response Heelgrasper - I'll give that a try.

TKR

[xorpt]

You should try to improve your lighting first. It is not equal on all parts of your document, so the upper left corner is much darker than the lower right corner. It means you will have to use gradients when post-processing. You can do that, using PS, Gimp or IM, but if your input is better, the better your output. Also, your pictures have lots of noise, probably because you are using a high ISO level on your camera, usually very bad on compact cameras. If you improve the lighting you will be able to use a lower ISO level, like 100 or 200, giving you more details and less noise

To remove the background, you usually play with the levels, setting the white and black points to reinforce the blacks and change the greys to white.

There are tons of methods to do this, using level adjustment (http://nyfalls.com/article-photoshop-levels.html), contrast-stretch, layering (see for example http://www.imagemagick.org/Usage/compose/#divide), etc.

[tkr]

xorpt
Thank you for the suggestions. I'll try them out.
Not being very experienced in photography - how does one identify areas of high noise in a pic ?

[Heelgrasper]

Not being very experienced in photography - how does one identify areas of high noise in a pic ?

By looking at it. Really, it's not more complicated than that.

For example, here's a bit of one of the images you posted cropped so you'll see at 100% (one pixel of the photo = one pixel on the screen):

IMG_0305-part.jpg (27.45 KiB) Viewed 8817 times

All you should see should be on a the black-white scale but here there are some yellow pixels etc. I other words noise. Your settings where f/3, 1/100 s and ISO 400 so it's not that surprising that the photo show some noise. The settings would also suggest that you indeed have to little light.

You might find it interesting to make a small test yourself by taking photos with the exactly same setup but changing the ISO (like 100, 200, 400 and 800) and then look at the same area of the photos. The higher the ISO the more noise you should see but there might not be much differense on 100 and 200 ISO.

[dingodog]

you should not save in jpg format if you want edit or post-process photos

I used jbig2enc

Code: Select all

jbig2 -s -p -v -T 115 *.jpg && pdf.py output>out.pdf

and this is the result (not optimal due to poor light and lossy format of jpg image)

http://ge.tt/8GKR39H