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On / Off topic - Matthias Wehrli - 07-03-2007

I updated my website....



- new HP-41 module list

- new photo gallery: HDR pictures



Matthias

www.hp-collection.org


Re: On / Off topic - Maximilian Hohmann - 07-03-2007

Hello!

Quote:
... new photo gallery: HDR pictures ...

Very interesting pictures, somewhat unreal! Of course, it would be interesting to learn a bit more about the technical backgrund! What camera/sensor/scanner did you use for taking them and how do you process the images?

Greetings, Max


Re: On / Off topic - Paul Brogger - 07-03-2007

Gorgeous. One of the train station pics is my new desktop background. Thank you!


Re: On / Off topic - Thomas Radtke - 07-03-2007

Have your HDR pictures undergone something like unsharp masking? They look a bit equalized for brightness. Extremely tasteful and interesting to look at, though.


Re: On / Off topic - Chuck - 07-03-2007

"They look a bit equalized for brightness."

============================================

That's what HDR does. You take 3 or more photos at different exposures and combine them. The HDR process combines the best parts of all (shadows, midtones, highlights, etc) to make a picture that usually a sinlge photo can't capture, but often it appears to be more like our eyes see it (because our pupils change).


Re: On / Off topic - Thomas Radtke - 07-03-2007

Ah, I thought there were already CCD chips capable for this range and that such a beast has been used :^).


Re: On / Off topic - Matthias Wehrli - 07-03-2007

Hi

I use a Nikon D80 and a very heavy tripod.
I normally take 11 pictures in 10MP: -5 to +5
I currently use .jpg quality as the .raw picture is much larger but the result isn´t really better.
The unsharpness is a normal result of this technic. It looks a bit misterious. Very interesting is the picture with the moving leaves.

Matthias


Re: On / Off topic - Maximilian Hohmann - 07-04-2007

Hello!

Quote:
Very interesting is the picture with the moving leaves.

Yes, definitely! Really looks like it was taken on a different world...


Just to play around a little bit, last night I re-processed a single raw-file of my camera (Sigma SD10 with Foveon sensor, which has a very good dynamic range) into a (pseudo-)HDR image and was impressed how much hidden detail this technique was able to reveal (for the price of incrased noise in this case): http://www.bombie.de/tmp/IMG08930_HDR.jpg


BTW, have you come across Helicon Focus yet ( http://www.heliconsoft.com/heliconfocus.html )? It is a somewhat related technique, that combines images from the same scene taken at different focal planes into one super-sharp "impossible" picture that is in focus everywhere (ideally at least). When you dont have enough planes or if you get moving objects in your scene, the effect is somewhat similar to your ghostly leaves: http://www.bombie.de/tmp/rapsfeld.jpg


It is really fascinating to witness, how increasing processing power changes (amateur) photography, I only wish I had a little more time...


Greetings, Max


Re: On / Off topic - Matthias Wehrli - 07-04-2007

Hi

Your pictures shows a airplane. In true HDR this is not possible as HDR doesn´t allow to take pictures of moving elements. How did you converted this picture into HDR?

Matthias


Re: On / Off topic - Maximilian Hohmann - 07-04-2007

Hi!

Quote:
How did you converted this picture into HDR?

I processed one singe raw-file with different contrast and brightness settings into four diffrent images: One optimised for the moon, one for the aeroplane, one for the smoke and one for the diffuse clouds in the background, then I combined these four images into this HDR (or pseudo-HDR, whatever you want to call it) image. The imaging sensor of my camera ( http://www.foveon.com ) is said to have twice the dynamic range (but less pixels) than the more common "Bayer"-sensors, so it is possible to extract all this information from a single raw file.

Greetings, Max


Re: On / Off topic - Meindert Kuipers - 07-04-2007

I do have some more experience with this, although I cannot disclose any details. I have worked with Bayer sensors with 12-bit dynamic range (per pixel!) which have the possibility of tweaking the amplifier settings. By taking the raw Bayer images and applying other filters much more information can be extracted. Especially since the green has double the resolution and has most of the luminosity information nice tricks can be done with this.

But this is getting way OT ...

Meindert


Re: On / Off topic - Maximilian Hohmann - 07-04-2007

Hello!

Quote:
I do have some more experience with this, although I cannot disclose any details.

Well, my experience with this is limited to something like 15 minutes... But what a pity that you can't tell us more! Quite a few years back I did my ph.d. on radar/microwave imaging and in the end you can sum it all up with "extract as much as you can from the raw data".

Hopefully, future raw-data converters that come with digital cameras will include some kind of HDR-function!

Quote:
But this is getting way OT ...

Well, if we write a little program that does the necessary calcultions for HDR image generation on an hp67, then we are back on topic, aren't we :-)

Greetings, Max


Re: On / Off topic - Dave Shaffer (Arizona) - 07-04-2007

re: "Quite a few years back I did my ph.d. on radar/microwave imaging"

Staying off topic (!), what exactly did you image? Was it single dish or synthetic aperture? I do radio astronomy interferometry, and we, too, are always trying to get that last little bit of information out of the data (usually by worrying about Fourier components).


Re: On / Off topic - Maximilian Hohmann - 07-04-2007

Hello!

Quote:
what exactly did you image? Was it single dish or synthetic aperture? I do radio astronomy interferometry, and we, too, are always trying to get that last little bit of information out of the data (usually by worrying about Fourier components).

We did high-resolution multi-frequency synthetic aperture (and "inverse synthetic aperture" which corresponds more or less to computer tomography, but with microwaves instead of x-rays) imaging of natural targets like plants and soil samples. One aim was to obtain a radar signature database for classifying satellite based radar images of the Earth. The european satellite ERS-1 was launched while I did my work, so we actually could test some of our methods on its early raw data sets. The other aim was to develop and test concepts for three dimensional imaging through interferometry and 3-D-inverse synthetic aperture radar at laboratory scale ( http://www-emsl.jrc.it/ )

So there are some parallels to your work, especially the Fourier components :-) And we used mainly equipment of hp in our lab - to come back to the topic - but no pocket calculators I'm afraid!

Greetings, Max

Edited: 4 July 2007, 4:29 p.m.


Re: On / Off topic - megarat - 07-04-2007

How do you merge the exposures into the final image? Do you use the "Merge into HDR" feature of Photoshop CS2?

(I only have a copy of CS, so I'm interested in any other techniques you might be aware of.)


Re: On / Off topic - Paul Brogger - 07-05-2007

That explains the ghostly figures walking on the platform . . .

Really, a stunning effect. Thanks again!

Edited: 5 July 2007, 12:28 p.m.