Hass Burn - HDR Example

[David]

Hi All - Discussion continues in this forum and elsewhere about the nature, use and properties of HDR images. Some photographers love them, others loathe them, and still others see the technique as another useful tool. Here is an example in which I have set out deliberately to make use of the power of tone mapping, and to see how it might deal with "slow" water flow .

Basic information: Canon 40D equipped with Canon 24-105 mm Zoom; set at 24 mm, Av = f22, ISO 100; Tv 5 stop values from 1/10 s to 2 s. RAW files processed via Canon's Digital Photo Professional (DPP) to TIFF files without any tweaking. TIFF files processed via Photomatix Pro 3.1 to give, to my eye, a realistic rather than OTT or surrealistic image. (Tone Mapping Parameters: strength 49%, saturation 46%, light smoothing very high, gamma 0.73, all other settings default.) The resulting 5 photo tone mapped image was then tweaked via the GIMP for wavelet sharpening and PSP9 for local contrat enhancement and tidying up.

The first image shows the central image of the set of 5. Clearly, there is a large dynamic range that the camera simply cannot capture adequately. (Note all these images are jpeg reductions from the TIFF files on my system so there may be some noise and distirtion not seen in the TIFF files.)



The second image shows the 5 photo HDR tone mapped image. Clearly, the tone mapping has been successful.



The third image is the result after tweaking.



Notes:
In this instance the HDR image and tone mapping have achieved what I set out to do. In addition, the HDR process has captured reasonably neatly the slow water effect.

I experimented with using only three of the images rather than five. The results were nearly identical, but the five image result shown here was "richer" in tones as shown by a broader histogram.

This example uses +/- 2 stops around the central image. There may be merit in going further, but practical constraints start to come into play, such as slight tripod movement from the water flow and from changing Tv values manually.

The location of the Hass Burn is near my cottage in Auchencairn, Dumfries and Galloway, Scotland. It is a spot used by local artists.

Finally, as always, comments and criticisms are welcome.

David

[Dave Humphries]

Hi David,

That's a very nice result, worth the effort I'd say.
Perhaps slightly over saturated (but I do that too!)

I'd be interested to know exactly what 'tweaking' was involved between images 2 and 3?

Thanks for posting, most informative.

[David]

Hi Dave - Thanks for the comments. Having come back to this post and looked at the final image again, I agree that it appears over saturated and slightly too contrasty. I think I overdid the local contrast enhancement.

As regards tweaking, I sharpened the second image using a tool in the GIMP known as "wavelet sharpening". This is a method that appears to be unique, at the moment, to the GIMP. It is one of three "wavelet" plug-ins written by someone called Marcor. Here is how he or she describes it:

"The wavelet sharpen plugin enhances apparent sharpness of an image by increasing contrast in high frequency space. The amount of unsharpness of the original image can be taken into account by adjusting the sharpening radius."

The other two plug-ins are "wavelet denoise" and "wavelet decompose". I may post more on these later as they are very smart.

Anyway, back to the tweaking: after sharpening I used local contrast enhancement as per McQ's tutorial. I originally did this in PSP9, but you can also do it in the GIMP. Some cloning tidied the image up.

Thanks again.

David

[Dave Humphries]

Hi David,

Yes wavelets are good!

I think ACR (Adobe Camera Raw) uses those methods for de-noise and sharpen in RAW conversion.
Also, the Neat Image noise filter plug-in for PS Elements also works that way (I think).

Thanks for the info on the tweaking, LCE with USM was my guess, and now you mention the tidying up, I can see a few of them - nicely done.
I used to love those 'spot the difference' cartoons when I was a kid (last week - yeah right).

Cheers,

[David]

Dave - re the wavelet stuff, thanks for info about ACR and Neat Image. I thought that when those guys talked about wavelets they were using manipulations involving Fourier Transform (FT) filtering, but I'm not sure. The Marcor wavelets do not use this technique, but two apparently idiosyncratic blend modes in the Gimp called Grain Extract and Grain Merge. If you've got time check out http://registry.gimp.org/node/11742

Cheers
David

[David]

It's no use - let the wrath of Shreds and Taken be upon me. I've cracked, I couldn't resist. It's the moon and cutiepie - it's an OTT version.



I promise I won't do it again.

David

[Dave Humphries]

Oh ....



My ....



Gosh !!!!



Hmmmm, Not that I wish to upset the great gods, but I was thinking a little texture over the top and it might pass as one of those "painted" images, interesting to see what Chuck makes of it.

Regards,

[Donald]

David

Re your pointing me, in another thread, towards wavelet sharpening. Managed to get it installed. Now, that is a clever little tool.

Donald