Hi, I have some multiple pictures I shot with exposure bracketing (e.g. 5 frames with +/- 2 EV). Now I want to blend those shots into one final picture.
I will do the blending in GIMP. But how am I supposed to proceed? After I select the shots I want to blend, do I first post-process those shots in darktable and than blend them in GIMP? Or I blend the unprocessed raw files, blend in GIMP, export the result (in TIFF?), and post-process the resulting single blended file in darktable?
If you used a tripod, you can merge them into HDR (not a tone-mapped image: a real, high-dynamic range one) in darktable, and develop / tone-map it there.
Another option, if the images were shot hand-held, is to convert them to linear TIFF in darktable (no filmic or sigmoid, no exposure compensation correction in darktable), align and merge the TIF files in Hugin, and process Hugin’s output in darktable.
Finally, HdrMerge can merge raw files directly into a DNG, correcting small displacements. I’ve noticed a loss of sharpness when I used it.
Hi,
I am not aware of any method to do HDR exposure blending in GIMP. I am willing to stand corrected if anyone knows of a way to do it. I believe Hugin is a FOSS option to do what you want. I have not tested this myself. BTW, if you have a Canon camera you can use the serial number to legitimately download there editing software which does HDR blending as well as panorama stitching.
Yes I have used gradient masks to blend two exposures in a landscape. I have also created masks using various options including creating luminosity masks.
LMs in GIMP
Load three exposures as layers dark, norm, light
Put dark on top and create LMs by Script-Fu>Create new>Luminosity masks (note LMs create a stack of masks above the dark layer)
Select a light mask to retain highlights
Layer>mask>add to selection
Activate original dark layer, create layer mask to selection
Get rid of selection
Experiment with which masks to deactivate to get desired effect.
Repeat the steps using the normal layer to lighten the shadows by selecting a dark mask invert?
You will need this script file to create luminosity masks. I haven’t used it for a while so I can only trust it still works in the latest version. luminosity_masks.scm (19.1 KB)
BTW, DTs processing with most digital cameras is so good that HDR blending is less important today. Multiple instances of exposure module and a gradient mask can work wonders with landscapes. I have also never seen a landscape that needed five exposures for blending. Two or three max is my opinion.
create hdr
Create a high dynamic range image from the selected images, and add the result to the library as a new image in DNG format. Images need to be properly aligned, which implies that they have been taken on a sturdy tripod. You can also generate HDRs with programs like Luminance HDR, and later import them into darktable for further processing. Note that darktable can only create HDR images from raw files.
I do not use a tripod (so normally go to Hugin to align the TIFs). Here is a bad example – hand-held raw files merged directly in darktable, so there are alignment issues. Please only consider this as a toning demonstration – and a bad one at that, I just applied a rather quick curve in tone eqalizer, then used sigmoid to map from scene to display.
You’ll come out with a different look if you exposure blend vs HDR fuse.
Do the one that suits you best. If you’re going to exposure blend, I say get your images as close to finished in your raw developer, then blend them in gimp.
The difference is that in one case, you develop 3 images, all LDR, all valid for a specific exposure range (shadows, midtones, highlights), and then you mix them together.
In the other case, you merge 3 images into one. Each image covers, let’s say, 14 EV, but with 2EV between them. Merged, you’ll have an image covering 18 EV. Of course, the screen does not come anywhere near that dynamic range, so you’ll use curves to darken/brighten parts. Darktable’s tone equalizer is not just a curve; rather, it’s an exposure control that works on regions, maintaining local contrast. It’s a very powerful tool that has a steep learning curve, but can give great results.
Simple answer is yes. Previously I used RT and exported a dark and light version of the “same file” as 16 bit Tiffs. Of course you could use two different exposures to begin with. However, now I use DT I just use drawn, parametric and/or gradient masks to achieve the look I want. I also find that very rarely do I need to be doing true exposure merging in most landscapes and a single excellent exposure will capture all the dynamic range I need.
I have a perpetual licence for Lightroom and have used that when required for HDR exposure blending. It can align hand held images. But because of the subscription model now I can not recommend that pathway.
It might be worth posting a set of images in Playraw and asking people to do an exposure merge so you can see the various techniques.
If you have a Canon the software will merge, but I tested it last night and it produces ghosting if hand held.
