gpyros
Key Veteran
Location: On a beach in Mexico
| Oh, man, here we go! One of my favorite subjects filled with misinformation, megapixels on digital cameras! 
The number of megapixels aren't nearly as important as you might think! It is what is ON each pixel that matters! Yes, quality, not quantity! 
I've regularly had images printed at 30" x 45", and also full bleed in magazines like "Sky and Telescope" which are known for their print quality. This with an old (4 years old in the digital camera relm is a REALLY old camera!) 2000 x 1312 pixel camera, which is only a 2-1/2 megapixel system!!!
What? How did he do that? No way! Impossible!
Yes. But what is on each pixel? Let's start with the lens - the MOST critical part of the system. I use Nikon AFS zoom lenses, 2.8 end to end on a 85 to 200mm zoom. Incredible glass, around $2k for the lens alone. The haze filter on the end is a "B+W" out of Germany, which adds a few hundred dollars - but what you get with a cheap generic filter is a little distortion and a little wavyness in the glass, which adds up to losing a bit of quality on each pixel. Why get a good lens if you are going to add blur before the light even gets to it?
The camera? A Nikon D-1. Not your usual bit depth of 8-bits per color, but 12-bits per. What does that do? Well, it allows me to process in Photoshop at 16 bit depth and pull out all sorts of things from the shadows and highlights that you normally lose with a typical system.
Don't save out of the camera in any compressed mode if you want to keep the quality - JPG is a lossy compression scheme!!! If you take a JPG image into your iimage editing program and do nothing more than save it again, then call up the saved image and save it again, it starts looking like a copy of a copy of a copy - and you haven't even done anything with it!!!!!! Always save in a lossless mode - TGA, TIF, whatever while you are working on it and save your master that way, then just drop down to JPG for web display or to send to your mother on the internet. That will keep the quality as high as possible if you want to do anything with it in the future.
OK, so your camera will only save JPG, what can you do? Start by making sure it is the highest quality JPG that the camera will save, most have a setting for this. If the camera has an option to 'sharpen' the image, turn it off, or all the way down. This is critical!
As soon as you get it to your computer, save it in a lossless format, at least you won't be losing any more quality than you have to, and work on it from there. Make it larger or smaller, adjust the contrast, whatever. As the LAST step, go into your editing program and add a little sharpening (in stock Photoshop use the Unsharp Mask function). This is after you have everything else done! And don't oversharpen, what will happen if you do is that you will get little halos at the edges between colors and all your work so far is wasted!
Whew, I'm glad I got that out of my system, I feel better now.
As an aside, what we use for feature film work is not 24-bit color, (32 with an alpha channel) but uncompressed 64 bit images - 48 bits for color and 16 for alpha (overlay)!!! Overkill? Not at all, with 24 bits of color you can see banding on a 50' screen (now that's enlarging!) but with 48 bits (remember that isn't just double, it is exponential!) you can't.
But here's a surprise - when doing effects work, film is routinely scanned at 2k - yes, only 2048 pixels across, for that 2-1/2 megapixel quality! But each frame is saved in a lossless format (Cineon, if you care) at 64 bit depth, giving you a 14 meg file - multiply that out by 24 frames per second and see how much storage you need per shot! Considering you will often have 5 to 10 layers for each frame. Good thing big RAID disks are getting cheaper...
Greg Pyros
Visual Effects Supervisor
Pyros Pictures, Inc.
www.pyros.com
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