Saturday, 30 May 2009

RAW, HDR and related resources

Since my post about RAW there's been a lot of interest and a number of questions have been thrown up. So this post gives links to and discusses resources that answer them and that I've found useful.

Expose so you bias the histogram to the right

...but without blowing the highlights.

In the full article from The Luminous Landscape, you'll read that most of the available levels of brightness that come out of a sensor's cell get allocated to the right hand side of the histogram, only a few to the left and a middling amount to the middle.

It's essential that you get this point because when you do you'll realise that the right hand side of the histogram is where you get most sensitivity to differences in shades and the left hand side the least.

Note that for HDR this means that you'll need more exposures for the shadows than the highlights to get the same number of shades (tones) in each.

The Luminous Landscape have also got a useful link to an article on understanding histograms.

Work in 16 bits for as long as possible

The topic of bit depth is covered in a quite digestible way here.

I only convert to 8 bits at the end of my workflow, when moving to jpeg:
  • I save my final file while it's still 16 bits so I can go back to it later, when needed
  • Then I convert to 8bit, do some final touch-ups such as noise removal and sharpening suited for the uses I'll put the jpeg to,
  • Then it's a save as, using jpeg as the file type.

Downloads and other links

Rawshooter Essentials

I still use Rawshooter for working with RAW, whether for preparing multiple exposures for my HDR workflow or the single 16bit TIFF ready for the Photoshop part of my workflow. It supports my Canon 350D's RAW files. If you do use it, it's vital

Before you download it, consider some things first. The company and software was bought by Adobe in 2006 and incorporated in Adobe Lightroom and Photoshop (see a tutorial on using their Camera RAW plug-in). Rawshooter doesn't support a lot of cameras released since the buyout, including Canon’s 5D, 40D, 450D/Digital Rebel XSi, and 400D/Digital Rebel XTi; and Nikon’s D40, D40x, D60, D80, D3, and D300. Download it here.

Noise Ninja

I use Picturecode's Noise Ninja to correct the noise I get in HDR work when I wasn't able / didn't(!) follow the advice in the article above... There's a free version but it only works on 8bit images, so useful only as a final step when converting to jpeg. Download here

DynamicPhoto HDR

I haven't tried Photomatix, though many swear by it. My own preference is DPHDR. Download here. The page gives a great explanation of where HDR is useful and what it does.

Video tutorial

I've put together a tutorial showing the processing from RAW to finished HDR image. It's twenty minutes long but don't let that put you off -- lots of people have said how they found it easy to follow and understand :) See it here.

The image used is one from my Urban Decay, Lost Spaces and Industrial Ugliness photo essay.

RAW explained in more detail

For those who want a more detailed explanation of how RAW works (rather than what it does for you, as I covered) read this.

That's all for this post. As usual comments, additional info, opposing views(!) are all welcome :)
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