News and Views from Dave Wilson

Tag: single

HDR Tip #1 – HDR From A Single Raw

by on Feb.28, 2011, under Photography

This week, HDR aficionados Rick Sammon and Trey Ratcliff are offering a week of HDR tips so I figured what better time to throw out a few tips of my own. I can’t promise to write one each day but I’ll try to get as close to this as possible. Without further ado, here’s tip number 1.


Caerlaverock Castle

Most of us who do HDR find ourselves in a situation once in a while where we would love to produce an HDR image but only have a single raw image to start with. Common causes for this are that we didn’t bracket when we originally shot the image we want to process now or that we want to take a picture that contains a lot of movement. In these situations, we can, however, still make use of Photomatix to produce an HDR-like image from that single original exposure and the results can often be very appealing. The image above, for example, was generated from a single exposure I shot while on a tripod-less trip back to Scotland a four years ago.

Many people, including several photographer friends whose HDR work I respect enormously, produce HDRs from single raw files using a workflow that goes something like this:

  1. Create 3 virtual copies of the original image in Lightroom.
  2. In the develop module, pull the first image exposure up by 2 stops so that it is brighter.
  3. Again in the develop module, pull the last image’s exposure down by 2 stops so that it is darker.
  4. Export all 3 images to JPEGs (hence creating the bracketed set you need to create an HDR).
  5. Open Photomatix and merge the 3 JPEGs together to give an HDR image which you can then tonemap and process as normal.

This sounds reasonable, doesn’t it? To create an HDR, you need a set of brackets and this gives you that set of images so all is well.

What these folks don’t realise, however, is that they are wasting about 20 minutes per picture and likely ending up with an image that is not as good quality as it should be.

Why not try this instead?

  1. Open Photomatix.
  2. Choose “File/Open…” and point it at the single RAW file you want to work on.
  3. Process as if you just merged a bunch of brackets.

“That can’t be right – it’s far too easy!” you are likely shouting by now. The truth of the matter is that this is likely to give you a better result than the long and complex “generate your own fake brackets” approach described above. The original raw file has at least 2 stops and most likely at least 3 stops more information in it than the JPEGs you create in the awkward workflow. The JPEGs you export there throw away all but 8 stops (8 bits) of the data so by using exposure modification to generate your pseudo-bracket,all you are doing is deciding whether you throw the information away from the highlights or shadows in the different JPEGs. You then open these in Photomatix and have it try to reconstruct the very same data that you were so careful to throw away in the export step.

Photomatix is perfectly capable of extracting all the information from your single raw file so why not have it do the work instead of trying to help (but actually making Photomatix’s job more difficult)?

People who have heard me talk about this before may note that I’m breaking one of my golden rules here which is never to have Photomatix process my raw files. HDRSoft themselves admit that Adobe Camera Raw (the raw file processor inside Photoshop and Lightroom) does a far better job of rendering a raw file than their processor so I always use Lightroom to export my brackets to Photomatix. If you want the best possible quality, you can do the same thing here as long as you remember one very important choice. When you export your single image from Lightroom to send to Photomatix (which, incidentally, you can do via the standard Photomatix plug-in by just highlighting a single image rather than a whole bracketed set), make sure you select “TIFF 16-bit” as the output format. A 16 bit TIFF file allows you to save every bit of dynamic range information from your original raw file and pass it over to Photomatix. If you select JPEG at this point, Photomatix will only receive 8 bits of information and can’t, therefore, pull out any extra dynamic range since you’ve already thrown all that data away.

Next time you are tempted to muck with your exposures in Lightroom and create a fake bracket, give this a try and see what you think. I’m confident you will see that in this case the easiest approach can also be the best!

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