How to improve graininess and halos

[jimbo1531]

Hi all, after months of research, months of trial and error and many different software programs I've come up with two HDR shots I'm really proud of and would like to get into it a lot more. Not sure though why they're coming out so grainy and dark, might be the camera I'm using. Also very bad halos. Any tips and criticism greatly received!

 

[KmH]

Digital images do not have 'grain'. They have digital 'noise'.
Digital noise is created in a photo when exposures are made outside the cameras dynamic range.
HDR or High Dynamic Range is a technique we use to try and expand the limited dynamic range our digital cameras have.

Noise becomes more visible in digital photos that are underexposed.
A 3 exposure series that has at least 1 in the series under exposed are blended together to make an HDR photo.
A typical series would be -2 EV, 0 EV, +2 EV.
The -2 EV image in the series will have image noise.

Many just dump the 3 image series in a HDR application and do no other preparation work to the 3 images in the series.
That lack of preparation shows up in the final image.
A further consideration is the bit depth of the image files you used. A 16-bit depth file (Raw or TIFF) has a lot more editing headroom than an 8-bit file does.
JPEG is limited to an 8-bit depth and is a poor file type to use for making an HDR image. Some JPEG files have no editing headroom.

A better approach is to edit the -2 EV exposure by reducing the visible noise in the image.
Unfortunately, noise reduction also usually softens image sharpness.
In fact, noise reduction and image sharpening are like 2 sides of the same coin, so some of the sharpness lost doing noise reduction can be recovered by adding some image sharpening.

Many don't appreciate how labor intensive making a high quality HDR can be.
Prepping the series of exposures before they are blended, and after blending then going back and forth between the HDR blending application (like Photomatix) that can only do global edits and a regular raster graphics application (Photoshop, GIMP, etc) to do local edits is a long and often quite complicated process.
(A global edit affects the entire image, A local edit only affects part of an image.)

Halos are often caused by over processing in the HDR application. If you are using Photomatix the Micro Contrast adjustment has to be used judiciously.
Videos tutorials on Photomatix and shooting for HDR photography

 

[Ironlegs]

Thanks for writing these very useful informations KmH, i still have to find a way to reduce noise and sharpen picture using GIMP.

 

[Scatterbrained]

First, I'd say both of these images were "left in the oven a bit too long". Looking at this gives me the impression that you're trying to get a finished image right out or the HDR engine. If you're using Photomatix that really isn't going to work. What I see in your shots reminds me of the "detail enhancer" presets. Your skies look like they are full of grey soot. Not a good look, and a side effect of heavy handed tweaking in Photomatix (full disclosure, I use Photomatix for my HDR work). As Keith pointed out, a good HDR is often the result of a lot of manual work, just like any other image.

For my personal workflow, I'll start with the images as raw files. Make the requisite global adjustment (mainly white balance and camera profile) then I'll use Photomatix to create a 32bit floating point TIFF file. I don't do any actually editing with the HDR program, all I want is that 32bit TIFF file. Then I edit that file in Lr just as I would a fresh raw file. Tone curve, sharpening, localized NR, dodging and burning, etc. Then it's off to Ps for more work, just like any other image file. The trick being to treat an HDR image like any other raw file, albeit with more dynamic range.

Beyond that, I would recommend spending some time getting to know the limits of your cameras dynamic range. I see many people spending a lot of time to create an HDR image of a scene that fit well within the DR of their camera.