Help with Gimp 2

SES posted:

Sorry for a sort of petty question, but I can't find the thread it belongs with.

It's not a petty question.  The answer may not be as simple as you'd like, but when you're starting from scratch, all answers seem fairly complex.  I'll do my best.

Someone recommended Gimp as a Photoshop alternative, so I downloaded the free version.

There is no "free version" of Gimp.  Gimp (the GNU Image Manipulation Program) has always been free Open Software.  It's complete and fully-functional.

I've got a photo that is darker on one side. Is there a way to gradually change the "exposure" as you go from left to right in a photo? Thanks!

Okay, since no one else seems to want to wade in on this one, I will tackle it.  Bear in mind that I used to teach this stuff, so this may be a bit pedantic.

1: When doing photo retouching (which is what you're doing here), there is a fundamental rule to keep in mind: You can't put detail back into an image (or image area) that doesn't have it in the first place.  In this case, you have an image that is way too dark to begin with, and fades almost to black on one side (improper long-term storage perhaps?).

I was once asked by a colleague if I could restore a family photo for her.  "Sure," I said, "just bring me the original and I'll do my best."  What she brought me was a tiny photo-booth image, obviously very old, and faded almost to invisibility.  I did what I could with it, but I doubt that she was really happy with the outcome.  We can do improvements, but miracles are still beyond our reach.

2: Okay.  With that in mind, let's proceed to your specific image.  I spent about fifteen minutes working on it with Gimp, with this result:

Here's what I did:

A: Open the Color/Hue control, and gradually raise the Lightness slider.  You'll notice that although the image improves somewhat, it can become rather bleached-out if you go too far.  That's unavoidable; image data that is already lost can be improved, but not completely recovered.

B: Open the Color/Hue control and gradually lower the Saturation slider.  This will reduce the soaked-in-molasses overall brown cast of the image.

I also selected the Red color control, and lowered the Red saturation value, which gave a further improvement.

C: This part can be tricky for a beginner.  You still have an image that's almost black on the right side, and we want to improve that.  Open the Free Select tool, and set the Radius to a high number (I used 75).  This is so there won't be a too-sharp boundary between the area we're about to alter and the rest of the image.  Carefully select the too-dark side, bearing in mind that you will have to accomodate particularly dim areas like the tunnel portals and the black locomotive.

When you've done that, open Color/Hue again (the selected area will remain selected) and slowly raise the Lightness slider.  Only the selected area will be affected.  Once you get it looking the way you think it should, you can deselect that area using the Select/None pulldown.  (On my Mac, the equivalent keystroke combination is Shift/Command/A; on a Windows or Linux box, it's probably Shift/Control/A, but you'll have to confirm that).

D: Having done all this, you'll notice that the image, while more legible, still doesn't look like new.  Remember my disclaimer about miracles?  There are other operations you can do that will help a bit.  One is to increase the image Sharpness, with the Filters/Enhance/Sharpen pulldown.  Careful fiddling with the Colors/Brightness-Contrast pulldown can help, too.

By all means, experiment with variations on all of the above steps.  You may like your results better than mine.

Some assorted tips:

1: CTRL/Z (CMD/Z on a Mac) will step you backward one Undo level.  If you screw something up, just CTRL/Z until you've Undone the unwanted action.

2: Your original image was scanned at 72 dpi and 13x9 inches.  I altered this to 300 dpi and 5x3 inches (Image/Scale Image), which makes for a larger file size, but seemed to improve detail a bit.

3: Once you have a bit of experience, I think you'll find Layers a very useful feature.

I certainly don't put this forth as The Only Way™ to approach your problem image, only as a method that a novice to image-editing software can apply with a minimum of background.  I encourage you to check out the many GIMP online tutorials for further instruction.  Be warned that it may seem intimidating at first, but remember, so was driving until you got some experience doing it.  And no, you're not likely to find PhotoShop any more easily digestible -- but it's a lot more expensive.

I know that this goes way beyond your original question, and also that I'm (perhaps incorrectly) assuming you're very new to image-manipulation software, so I apologize if this is too much of an infodump.  I was hoping some others might find it useful, too.

Yes, there is.  

1) Go to Colors -> Levels.  

2) click the "Auto" button.    

3) Next to the Auto button, you'll see three droppers.  The righthand one is the white levels dropper.  Click it on a white item towards the darker side of the picture.  Click "Okay" to save changes.  

Hope this helps!   

Mitch

Here is my attempt using Paint.net.  I copied the picture and created 2 layers.  The first layer I adjusted the over all levels.  The second layer I adjusted for the dark portion.  Once I had the dark portion where I wanted it, I erased part of the first layer with a feathered tool to blend it.  Once the 2 layers were blended I did a little color correction of the darker layer.  Not perfect but not bad.

Well, you did better at us at bringing out the mountain details on the right hand side, anyhow, Marty.  Good show! 

Following Marty's idea, and adding an inverted layer in Divide mode and a color overlay over the right hand side to reduce the green a bit:  

Mitch 

Mitch and Marty,

Thank you, guys, very much! That all is just what I need. I am indeed a total novice at this. I greatly appreciate your time.

Steve

Guys:

Let us also thank BALSHIS for an excellent write-up.  Perhaps a bit over the top for some, but delightful for my analytical and technically-inclined brain.  I know my way around GIMP, but I found the tutorial quite helpful, and I agree with the detail points.  That likely took some time to compose, and I appreciated it.  I am a bit of a FOSS (Free-Open Sourse Software) junkie, and welcome any chance to use it.

Thank you, Nate.  Glad to be of service.

--John

YES! THANK YOU BALSHIS. That's the guy I most meant to acknowledge. I apologize; I'm still getting used to this forum's format and seem to confuse signatures with salutations.

Steve