Despite the title, I am not "pr0" by any means. However, I do believe that this may help some of you who are struggling to start rendering stuffz in Photoshop.
Anyways, if it helps you, great. If it doesn't, well it was good practice for me drawing these XD. I can say "I halp'd Nolani" AND I can slightly tick espy off because of the gratuitous hard-edges and smooth shading

Intro:
While this tutorial pretty much assumes you have a tablet pen and photoshop, there are concepts here that I believe will be useful for any painter.
Render: To represent in a drawing or painting, especially in perspective. Here it means using color, value and shapes to represent your image realistically.
While not everyone wants/needs to draw realistically, it does help you stylize in a way that makes everything all the more believable. Rendering is something that can be hard for people to learn. However, learning to render light can be extremely useful in creating a immersive painting.
Personally, I hate rendering. It sucks. It's boring and micromanage-y. Still, I have to learn to do this if I want to become a better artist. This tutorial is something that is probably even more useful for me to create as it might be to you guys reading it.
I encourage taking a simple household object (preferably round-ish so you don't have to worry too much about perspective) and rendering it out. Art is interactive: it helps you much more to do it than just to read about it.
Feel free to post your attempts here, so that we can help you see where you did well and where you can do better. I PROMISE no trolling at ALL for those who are making a genuine effort :P
Tutorial:
First step, simple. Sketch out whatever you are drawing.
Try to include the shadow if you aren't too comfortable with just blocking in colors.
I personally use a hard round with shape dynamics turned on in photoshop do this part, as I feel like it gives more of a expressive line.
Do try to use long single strokes instead of many tiny ticks.
Second step. Start blocking in the colors. This can be hard to people who are not used to painting. Try to see the exact colors, and not just what you know the colors can be. The local colors can vary drastically under different types of light.
Try do things without using too many layers. It will give you a more visceral painting feel. I did this tutorial with one layer (actually 3, because I wanted to save the steps).
Like in this example, the harsh incandescent light made the onion a lot more yellow than it really is. The onion would be more red in normal daylight.
Do not use neutral grey or black for the shadows. There is almost always some color in the shadow, try to capture the warm or coolness in your colors.
If you are having real trouble getting the colors right, something that might help would be to squint at the subject so you block out all detail. See if you can pick a color for each of the major areas and just make yourself a mini pallette.
Third step. Start rendering out the shape of the subject. This is where you do blending and all that other good stuff.
Blending is the act of smoothening out edges when painting. In this phase, target areas that have smooth curved surfaces, and try to represent that by making a gradation of colors and values. Do not try to use the blur tool or the smudge tool here, as the results will look textureless and it's very possible you will reduce saturation of the colors by averaging the values. Do yourself a favor and use the brush tool :P
To blend with a brush tool, just use the [alt] hotkey to sample colors, then use a low opacity brush or a large soft brush to make a local gradient on the surface of the object.
You can technically blend with any brush, as long as you use opacity and flow dynamics. I do not recommend turning on size dynamics, because it can lock you in doing stuff with the wrong brush size. Just use the [ and the ] keys to change the sizes of the brushes.
I don't really have too much to say about rendering. Basically try to smooth out some parts that need smoothing out. Don't blend everything though. Remember hard edges give people hard-ons, so whenever you have a clear distinction between two objects or surfaces, a hard edge will give you those extra oomph points.
You can add some texture for more realism in this stage. Best way to do it would be to grab some custom brushes, or make your own. I'll do another tutorial for that later.
Edit: Changed the onion_3 picture because I realized the shadow should be cast further back. XD It's good to look over your drawings a couple times because you tend to find mistakes :P
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Well that pretty much wraps up how I render. Make whatever you want of it.
Ask me or any of the other artists here questions if you need it.