A lesson in photo manipulation.
polycounter lvl 19
Working with UDK's colour grading has shown me one thing: I'm pretty ignorant to key important features of manipulation within photoshop. That is: Curves, Gradient Maps, and Levels.
Sure, I use these from time to time (levels especially), but I have very laymen relationship with them that I'd like to grow.
'Adam, seriously? The curves tool adjusts the curves of the image.'
Ok, I get that, but I don't know if I quite get what curves are.
Does anyone have links that outlines what these adjust, specifically? Or are willing to write/talk about them? I'd love to read it.
Thanks!
Sure, I use these from time to time (levels especially), but I have very laymen relationship with them that I'd like to grow.
'Adam, seriously? The curves tool adjusts the curves of the image.'
Ok, I get that, but I don't know if I quite get what curves are.
Does anyone have links that outlines what these adjust, specifically? Or are willing to write/talk about them? I'd love to read it.
Thanks!
Replies
By raising up the darks, moving the slider from the left to right in levels, or moving the left node up, you're essentially making all blacks less black. By adding a point the the middle of the curve and adjusting the curve you can change how quickly the blacks become white (reaching the very top).
You'll see a graph in the background, what this graph represents is the ammount of information in the texture in that tonal range. If you have an image that's very bright and has almost no darks are greys, you'll notice the background graph is lumped way to the right side, so if you move the slider or the curve to start at the base of the left side of this "mountain" you're basically telling it you want that very bright tone to be black. This gives your image more contrast, it will make your image run the gamut of pure black to full white.
What you want to avoid in the curves editor is any flat peaks, as that will destroy any detail you have in your image. It's the contrast that gives you the detail, so when it flattens out the "lines" that define shapes go away and you get stuck with flat grey areas. If you have a flat peak in the middle of the curve you'll see that the mid tone areas look flat.
So basically when looking at the curve, look for the areas in the graph in the background that have the largest spikes, this is where fine tuning adjustments will make the greatest affect on your piece. And generally try to match the slope of the background graph with the slopes of your curves, this will keep the detail of the image.
Isolating color channels like red blue and green can be nice for adding subtle hue changes but i wouldn't advize going crazy with it. And on almost no occasion would i ever recommended having the slope of the curve point downward, what that does is makes areas black white and areas that are white black, it totally throws of whatever sense your image had going on, but if you want some weird metallic effects or psychedelics it can do some ok stuff.
The auto function is also pretty cool, it tries to auto create contrast levels to give your image more tonal range and make it "pop" a bit more.
I often use the auto button and tweak it from there.
This website is awesome. Thanks for sharing it !
I went through the CS3 series a while back, but I'd imagine they'd still be useful and relevant to those using CS4 or CS5. I'd definitely recommend them if you're looking for something quite comprehensive.
Not trying to hijack the thread or anything, but does anyone have a good tutorial link on blending layers. Currently I use the standard Multiply, Overlay, softlight, screen, color dodge and occasional hard light. I understand these. But on some of the others I'm not so sure. Pin light for example. Would be cool if someone had an explaination for each and how they use it typically.
From an artist's perspective:
http://www.myinkblog.com/2009/07/14/an-explanation-of-photoshop-blend-modes/
From a coder's perspective:
http://www.nathanm.com/photoshop-blending-math/
Curves give you a crazy amount of control points that you can add. You can get some unexpected results....that can also be a good thing.
I mostly use it for contrast control and value control.
Hope that helps..:)
example:
If you take the bottom left anchor and drag it straight up 50 steps then the darkest tone in the image will be RGB 50 (which would decrease the contrast without affecting the highlights, and also remove 50 RGB tones from your image dropping the maximum number of value steps to 205). If you were to drag it directly to the right 50 steps then all the RGB values that were less than 50 before have tranformed to 0 (increases contrast and destroys all shadow detail that was below 50).
Curves are really useful for color balancing since you can tweak mid tones, shadows, and highlights separately and you can combine the curves tool with the eye dropper and the color sampler tool for really precise work. Assuming your image has no blown out highlights you can adjust global color casts by mostly working with the top right anchor (dragging it down, not up so as not to blow out highlights). You have to be really careful when color correcting to not introduce odd shaped curves that might create a color shift in only the shadows, or only the mid tones since those can become really hard to correct. In general gentle curves will produce predictable, controllable results and curves with sudden spiked will produce broken looking images.
If your image does have blown out highlights then you are going to need to work more with the mid tones so that your blown out white areas stay white and don't turn to a pastel color.
There have been some really good resources shown so far, but I'd like to share my experience. I personally learned how to really understand this stuff by taking a normal photo, and trying to use levels and curves to achieve very specific effects.
I highly suggest trying to take an image and achieve a range of specific photographic effects using the limited toolsets of color curves, levels and saturation. It really helped me understand how to use these tools more effectively, and become well versed in color correction.
http://www.danielscholten.com/photography/recent/duotone-night.jpg
http://farm3.static.flickr.com/2081/2185794657_dae8279f6e_o.jpg
http://farm3.static.flickr.com/2193/2274598406_9ee2ffbd5c.jpg