Adobe HDR Merge Test

June 11, 2010

I’ve been excited about a special location I’m visiting tomorrow for a shoot and I spent the evening learning a bit more about HDR photography. Adobe Photoshop has an auto-import wizard to merge multiple, bracketed shots into an HDR image. First you shoot several images, maintaining the same ISO and f-stop, changing the Tv. If you change the f-stop you alter the depth of field mid-merge and if you choose an ISO other than the smallest available in your camera you’ll just introduce more noise.

Then you select the photographs in the import tool. It gives you a quick thumbnail overview for all the shots; it’s good to pay attention to this because in one instance I accidentally imported a photograph that wasn’t part of a bracketed series and didn’t realize it until later on.

I used the local-adaptation method of HDR merge. Here you set the pixel radius for microcontrast, as well as the threshold. If you set the threshold too high you’ll get haloing/banding of your tones.

You can tweak the tone curve in this mode, just like regular curve window. Here’s an example of a tone adjustment I made. The left hand spike is the dark ground regions. The right-hand spike is the sky region. You can use multiple tweak-points to give a nice contrasty spike for whichever regions of the tone you want. Here I made the ground region ultra-contrasty.

One thing I noticed is that the branches of the trees in front of the sky were shifted in tone due to the micro-contrast radius setting of the HDR merge. I think I would need to lower the micro-contrast radius or try to keep things like that from happening in the original composition of the shot.

I performed these experiments so that tomorrow I have a better picture of what the end-results look like when photographs are merged together. I plan on keeping this in mind as I shoot so I can attempt to compose my images in the best manner possible to take advantage of what Photoshop’s HDR merging can bring.

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