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Tag: HDR (page 2 of 2)

Making Garish Images with GIMP

This isn’t a tutorial so much as it notes for myself regarding some of my recent experimentation in GIMP.  The resulting images are garish, but I find them oddly compelling.

Here is a crop of a photo that I took from my driveway.  The original photo was 6000×4000 pixels.  I performed the various operations described below on the full size image.  Only later, after I saw what the image looked like after doing various manipulations, did I crop it to 1600×1080.  It is a kind of blah photo.  Aside from the crop, I performed no other manipulations on this image.  I should note, however, that it was one of the HDR images produced by my NEX-7.

Next, I performed one round of Gaussian Blur, Grain Extract, and Grain Merge on the photo.  I used a blur radius of 50 because I noticed that I was getting a large halo around trees and along the skyline when I used large values.  I still need to do more experimentation to find an optimal value.  Alternately, it may be possible to mask the problem areas to avoid this issue.  Here is the result:

In Easy Overprocessing with c2g, I found about GIMP’s c2g filter.  I’ve tried the techniques described on that page, but haven’t yet gotten similar results.  It may be that I’m missing a step.  Another interesting article about c2g is How to Make Stylish Black & White Digital Photos with the GIMP.  I’ve skimmed it and it’s worthy of further study.  Another good article is Black and White Conversion with GEGL’s c2g (color2gray) in GIMP.  It provides some very, very helpful hints on how to best set some of c2g’s parameters.

The c2g operation converts a color image to grayscale, but the resulting grayscale image can be much more striking than just using Colors->Desaturate… In GIMP 2.6.11, the c2g operation is found under Tools->GEGL Operation…  From there, a dialog will pop up, at which point,you need to select c2g from the menu. Here is what the crop looks like after subjecting the entire 6000×4000 image to c2g with Radius=500, Samples=10, and Iterations=10.

Here is what a desaturated image looks like using Colors->Desaturate…  I ended up using a portion of this image for the sky.

The c2g version appears to have more texture to it.  The sky, however, turned out to have too much texture for my taste, so I created the second version to use for the sky alone.  I applied a layer mask containing only the sky to that layer and an inverted mask to the c2g layer.  With the masks applied, I set the layer mode to Grain Extract for both of these layers.  Here’s what that ends up looking like:

Note that the sky has a fairly smooth texture to it, but the buildings and even the street appear to have a significant amount of texture.

Next, I duplicated the blur-extract-merge layer that I started with, put it on top of the layer stack, and set its mode to Grain Merge.  Here’s the result with those four layers visible:

This might actually be a good place to stop, but I decided to see what it looks like by duplicating the two grain extract layers and the top-most grain merge layer and then placing those layers in the correct order on the top of the layer stack.  Here’s the result:

Performing another round of duplicating the grain extract and grain merge layers and placing them at the top of the stack produces this image:

I wanted the sky to be a deeper blue, so I added a grain extract layer of the desaturated sky with the opacity set to 71%.   Here’s the GIMP layer window for the upcoming image:

Below is the final image.  It may be that one of the earlier images is “better”, or maybe they’re all just awful.  I’m too close to it right now and probably need to look at the whole thing again in a few days.  It is interesting though to see the variety of contrasting colors obtained using this technique.  At no stage in the process, except for the last step where I fiddled with the sky color, did I actually choose any of those colors.  They just came out on their own by iterating grain extract / merge operations on the grayscale image produced by c2g.

Sony NEX-7 in-camera HDR Example

My Sony NEX-7 does in-camera HDR.  I used this feature extensively while taking photos during my recent vacation.

HDR stands for High Dynamic Range.  HDR photos are intended to show you portions of the scene that might not otherwise be easily visible when photographed with just a single exposure.  The way it normally works is that several – usually three or more – exposures are taken of a scene, usually using a tripod.  The exposure settings are changed each time so that portions of the scene that aren’t well lit in one exposure will, hopefully, be better lit in some other one.  The photographer then takes these various exposures and edits them together to make a single photo that better shows the scene.  Software exists which helps with this process.  I haven’t used any of this software, so I can’t say how well it works nor how easy it is to use.

On many of Sony’s recent camera offerings, you can put the camera in HDR mode.  When in this mode, a single press of the shutter release button causes three exposures to be made – i.e. three different shots will be taken at differing metering levels.  The camera saves the middle exposure unaltered to the flash card, then goes to work on processing the three photos it took into one single photo which may or may not be “better” than the shot taken using the middle exposure.  This middle exposure is what the camera would have recorded had you simply taken the photo in some other (non-HDR) mode.

You can, if you wish, tell the camera how to bracket the shots.  I tried this on my first day of using it, but some of the results were quite horrible, so I put it into auto-HDR bracketing for the remainder of my shots.

Even so, some of the HDR shots in auto-HDR mode aren’t that good; many times I like the non-HDR version better and am glad that the camera recorded that version.

Other times, I can see only minor differences between the HDR version of the photo and the non-HDR version.  It can provide good results, however, when there are areas of shade or shadow in the scene.  This happened quite frequently when taking photos of arches and fins in the Moab area.

Here is a non-HDR exposure taken at the Grand Viewpoint in the Island in the Sky district of Canyonlands National Park.  Note that the foreground is difficult to see because it’s quite underexposed.

Here is the HDR version that the camera composed of the same scene.  No editing of my own, aside from scaling, has been performed on either this photo or the one above.  Note that it is now possible to see some details of the foliage in the foreground.  I should note too that I did not use a tripod for this shot.  I tried to hold the camera as steady as possible.  Even so, there’s some camera movement.  Sony’s HDR in-camera HDR processing somehow manages to correct for small movements of the camera between exposures.

Finally, here is an edit that I did of that last photo.  I made the foreground somewhat easier to see while still conveying the fact that it’s in the shade.

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