Super resolution – The tour de force of image stacks
Super-resolution in Lightroom and Camera Raw quadruples the resolution of raw files. Photoshop’s image stacking technique improves resolution.
Super-resolution with Photoshop, based on the stacking of twenty or so images, makes it possible to increase the resolution of a camera body, such as the 20 MP (5184 x 3888 pixels) of a 4:3 sensor. It delivers an 80 MP (10506 x 7864 pixels) file with optimum resampling. However, it’s only suitable for static subjects. The central figure wasn’t entirely static during the shooting. The moving water in the canal creates a mirror effect. Olympus EM-1 MkII, 25 mm.
The basic file size is 20 MP.
Lightroom’s super-resolution creates artefacts.
The technique of stacking layers of 20 views of the same subject improves detail.
Sometimes you just wish your camera had a higher resolution. If you don’t want to change your camera, Lightroom’s Super Resolution feature offers a powerful way to increase image definition. It allows you to create DNGs with four times the resolution. For example, a 20 MP image becomes an 80 MP image. The performance of the resampling algorithms does not offer the sharpness and details of a ‘pixel-shift’ shot, but the result is more efficient than the various resampling modes offered by Photoshop and easily rivals Topaz Gigapixel AI. Nevertheless, the resampling process produces artefacts. Photoshop’s image stacking technique, another super-resolution process, can overcome these shortcomings. The results are surprising in terms of detail recovery and noise reduction. The only caveat to this technique is that it only works well with static subjects. Here’s how it works.
1/ Super-resolution DNG
Select the images you want to resample. Super Resolution (Enhance… > Super Resolution) will increase the size of the images by using the algorithmic resources of machine learning. The processing time shown in the window is a guide. Operation depends on computer performance. Images are automatically saved in DNG format.
The DNG images are then opened as layers in Photoshop. As the final file will be heavy, in order to reduce the load on the computer, we set Lightroom’s external editing preferences to 8-bit instead of 16, and the following parameters: Tiff, Adobe RGB, 300 dpi. If your computer supports it, you’ll be able to work in 16-bit.
2/ External editing
External processing parameters can be changed in Lightroom Classic > Preferences (Mac) or Edition > Preferences (PC). Although Adobe Lightroom recommends ProPhoto and 16-bit, choosing Adobe and 8-bit will avoid managing a file that is too large in Photoshop.
3/ Editing in Photoshop
Right-clicking on the selected images in Lightroom will open them in Photoshop with the following option Edit in > Open as layers in Photoshop. Stacking may take several minutes, depending on your computer’s performance.
4/ Save the file
The file is saved for security reasons. Being 5GB, must be saved in PSB large document format as Tiff is limited to 4GB.
5/ Select all layers
All layers are selected (Select>All layers) in order to align them in the next step.
6/ Layer alignment
Layers are aligned in automatic mode (Edit>Auto-Align Layers…), without lens correction. It might take a few minutes (5 minutes with a MacBook Air M2). You can hide/show each layer to check that the alignment is correct. If there is a noticeable shift, you can delete a layer.
7/ Dynamic object
All layers are selected again and converted to smart objects (Layer>Smart Objects>Convert to Smart Object).
8/ Median stack
Then select Layer>Smart Objects>Stack Mode>Median. Moving objects and noise disappear. Unwanted content and defects are removed. The image will be more detailed and sharper, but a little softer.
9/ Sharpen
Sharpening restores the sharpness of the image (Filter>Sharpen>Sharpen or Smart Sharpen). As the file is a smart object, it is possible to revert to the sharpening setting. Make a copy, flatten it and save it as a Tiff. The image will be much lighter.
Discover the photography courses at Spéos
Spéos offers various training courses ranging from simple one-week photography courses (initiation and advanced level) to 3-year courses. The long courses to become professional photographers allow you not only to master all the photographic techniques and its vocabulary (blurs, hyperfocus, sharpness zone, depth of field, backlighting, focal length, shutter release, autofocus, wide-angle, rule of thirds, etc.), but also all the stages of shooting and image processing.
Visiting the school allows you to discover the premises, the studios and the equipment, and is undoubtedly the best way to familiarize yourself with your future way of working. This is why, in addition to the open days, Spéos offers throughout the year personalized visits by appointment to come and discover the school with a member of the team.
Text and photos: Philippe Bachelier, teacher of Printing techniques at Spéos
