Introductions
OpenEXR’s can be mysterious things. My first couple encounters with them left me initially underwhelmed. Why did it look all washed out? Why’s the file size so bloated? Why didn’t they just send me a .TIF? I had been more of a .TIF, .TGA, PNG man most of my computer imaging life and OpenEXR just wasn’t getting me excited. Then Max 2010 and the Connection Extension changed everything.
What is it and where did it come from?
First off OpenEXR is a High Dynamic Range (HDR) image format created over at ILM which is now their standard file format for all of their film work. You can work in 16 or 32 bit at full float, half or full integer. Not every app plays nice with all EXR encoding so it is best to use the default settings the Connection Extension suggests in most cases. Now why go to 16 or even 32 bit? More color data per pixel means there is a wide range of pixel color values stored for each pixel. This is the wonderful thing about HDR formats. More data means more flexibility post render.
Why should I be interested?
Did I mention the flexibility post render? Here are some reasons to be interested:
- -Re-Exposure (Like bracketing your camera, but after the fact)
- -Multi-Pass Rendering (You can store all your passes in one tidy .EXR)
- -Color Correction (More pixel color data means more accurate and dynamic color adjustments)
Re-exposing low bit depth images is little more than crushing pixel color values together or pulling them apart often leaving unwanted gaps which to the eye looks like banding. With so little headroom in the data there’s not much you can do but tweak in small increments. With OpenEXR you can push the exposure around and still retain image integrity. Detail you didn’t even know was there emerge from the shadows or blown out areas. When you add multi-pass to this scenario things become very flexible and the true power of Open EXR is revealed.
Next Time
That’s it for Part I. In Part II we’ll look at some examples and the Max end of the EXR single and multi-pass workflow. First post in the can, not too painful. Now what was I supposed to be doing?