HDR - Blended Images - Resolving Exposure Problems

HDR - Blended Images - Resolving Exposure Problems

One of my initial images from Assignment 2 was producing an image of the kitchen. In my blog you'll notice how I struggled with eliminating the shadow from the light on the left of image.

As an experiment I've gone back to this same situation and using my histogram and exposure compensation I will demonstrate, to myself at least, the HDR option to this problem.

Using a tripod and going back to my kitchen I've taken an initial image using the camera's matrix metering for an average exposure.

From this initial image there is over exposure at the light source coming through the window and under exposure, as I suffered from before, on the left side of the floor caused by the kitchen units causing shadow. 

The histogram is showing the dynamic range of the scene is greater than the camera sensor can cope with, it displays both shadow and highlight clipping.

My plan is to first eliminate the shadow clipping which I can see on the histogram if I get some space between so I have started by over exposing 1 full stop.the blacks at point zero, I will of course have highlight clipping also shown on the right of the histogram. There is still shadow clipping so I shall overexpose 1 stop further

I've over exposed now 2 full stops and I can see from the histogram on the camera LCD that I'm no longer shadow clipping with a small space between the blacks and the start of shadows being recorded. I shall now repeat in the same way to under expose a full stop at a time to eliminate highlight clipping

At 1 stop under exposed the camera LCD histogram is showing me I still have highlight clipping so I shall under expose another stop

I'm now at 2 stops under exposed and the histogram shows me I am still clipping highlights so I shall take another image but a further stop under exposed. Its the light from the window that is causing the over exposure.

When viewing the Camera LCD it appeared that I was no longer highlight clipping. Whilst minimal highlights are being clipped there still some clipping. However at this point I no longer under exposed any further

I now have a series of 6 images covering a dynamic range of 6 stops. Blending this 6 images should now create me a HDR image with a wider dynamic range that what the sensor of my camera was able to record.

Whilst the dynamic range of the image is good I have some colour casts from using Photoshop to create a HDR from the RAW unprocessed files.

Using Photomatix I have merged the jpegs and tone-mapped them making no manual adjustments.

Using photomatix I no longer have the colour cast on to top left of the image (ceiling).

I'm not quite sure why there is a big difference, perhaps the HDR capability of photomatix is better than Photoshop. Photomatix is probably the most used / best liked tool so perhaps this is why the final result is better

Anyway this was an interesting experiment to create an image that contains the full dynamic range of the scene. The view that my eyes recorded was very similar to the photomatix HDR image. This again proves that the human eye can record a higher dynamic range than a camera's sensor

Of course viewing the scene with my eyes scanning the scene and focusing on elements within it could be likened to create HDR video in my head.

I often search Luminous Landscapes for information and there is an interesting article called Understanding Histograms which can be found here:

http://www.luminous-landscape.com/tutorials/understanding-series/understanding-histograms.shtml