GIMP?

[fatsheep]

Is it possible to do HDR in the GIMP? I found this tutorial but I've been told it's actually DRI and not a true HDR. I'm going to try my hand at HDR pretty soon so I was wondering if the above tutorial is a good one to follow for GIMP?

It seems like most people use Photomatix or Photoshop, has anyone here tried using GIMP or a freeware (hopefully Linux compatible ) program?

[Mr. Pickles]

Try this.....should work in GIMP, PS, etc...

- Take photos- one exposed normally, one 1 stop underexposed, one 1 stop overexposed, from a tripod (or use a RAW file saved with these adjustments)

- Open middle image as background

- Open dark (underexposed) image, copy, paste into new layer in composite image, rename layer "Dark"

- Desaturate dark image

- Adjust curves on dark image to set levels

- Create a layer mask on Dark layer, copy monochrome dark stock image, paste in to layer mask and anchor

- Do the same for the light (overexposed) image- open, copy, paste into new layer, rename layer "Light", desaturate original stock image

- Invert colors in stock image, adjust curves if necessary

- Create layer mask on Light layer, paste inverted gray scale light image into it, anchor

- Save image

[fatsheep]

Thanks for the instructions. I went out and took some pics and I'm trying this but I ran into a few roadblocks:

Originally Posted by Mr. Pickles

Try this.....should work in GIMP, PS, etc...
- Adjust curves on dark image to set levels

I know where the curves tool is but I'm not sure how to use it effectively. The help manual wasn't too much help either... I just messed around with it until I found a setting that looked good.

Create a layer mask on Dark layer, copy monochrome dark stock image, paste in to layer mask and anchor

So I am pasting the desaturated dark image into the layer mask for the dark layer? This would mean I would have the desaturated dark image for both the layer and the layer mask.

[jfrancho]

No. You are blending exposures. Not a HDRI.

[Mr. Pickles]

Then what exactly is an HDR image...if it isn't a blend of several exposures?

[fatsheep]

Originally Posted by Mr. Pickles

Then what exactly is an HDR image...if it isn't a blend of several exposures?

Well I read through the tutorial I posted a link to above and I think I was misreading your original post. You meant for the dark layer to remain colored and only have the layer mask for the dark layer be desaturated correct? Well I did this and messed around with the curves and I ended up with this:



It's nothing spectacular but considering how bright the sky was and how dark the house was, I think it turned out well.

[Mr. Pickles]

As long as you got more range in the image, you got it figured out. Could tweak more to spread the range even more...

[fatsheep]

Originally Posted by Mr. Pickles

As long as you got more range in the image, you got it figured out. Could tweak more to spread the range even more...

Yea I definitely did get more range.

Middle exposure:





Here's the composite again:



I was able to tweak the sky to my preference and brighten up that house quite a bit. I'm really liking this technique. Thanks for the help.

[jfrancho]

Originally Posted by Mr. Pickles

Then what exactly is an HDR image...if it isn't a blend of several exposures?

A High Dynamic Range Image (HDRI) is a 32 bits per channel radiance file created from three or more 8 or 16 bit per channel non linear Low Dynamic Range (LDR) image files. Period. Lets try to keep the nomenclature consistent.

[Mr. Pickles]

I think your friends at Wikipedia differ on your definition, as do I on the 32-bit reference. Maybe Photomatix is 32-bits? Otherwise, it is a high dynamic range image made from several others that are blended together, in its simplistic form.

From High dynamic range imaging - Wikipedia, the free encyclopedia

In computer graphics and photography, high dynamic range imaging (HDRI) is a set of techniques that allows a greater dynamic range of exposures (the range of values between light and dark areas) than normal digital imaging techniques.
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HDR images require a higher number of bits per color channel than traditional images, both because of the linear encoding and because they need to represent values from 10−4 to 108 (the range of visible luminance values) or more. 16-bit ("half precision") or 32-bit floating point numbers are often used to represent HDR pixels. However, when the appropriate transfer function is used, HDR pixels for some applications can be represented with as few as 10–12 bits for luminance and 8 bits for chrominance without introducing any visible quantization artifacts.

[jfrancho]

Take a look at the discussion of this particular article. Plainly, its outdated, incorrect and sucks. This happens in Wikis.

[jfrancho]

Maybe Photomatix is 32-bits?

Any true HDR Imaging tool will allow you to create a 32 bit/channel file, even Photoshop.

[fatsheep]

Technicalities aside, this "blend of exposures" is the same concept as HDR correct? How would I tell how many bits GIMP utilizes? I'm assuming the more bits an image has, the broader a range it ran render?

[jfrancho]

No. True HDR examines the image and builds a 32 bit per channel file pixel by pixel. Blended exposure images do extend the DR, but they are not an HDRI.

[Mr. Pickles]

So it is a 32-bit deal, then the Wiki thing is plainly wrong, then any true HDR software will allow you to create a 32-bit file, then it builds a 32-bit one.

Whatever the heck it is, it is an artificial increase of normal dynamic range, and it can be overdone, and often times is.