Let there be light: NANLITE Forza 500
Each professional challenge has the opportunity to step out of your comfort zone, push your boundaries and learn something new. That is why I was delighted when the Salzburg museum approached me to photograph the ceiling fresco of a church in Győr for one of their upcoming books.
Of course, this task alone should not seem like a great challenge. However, that fresco is located above the gallery of the Benedictine Church of St. Ignatius of Loyola in Győr, which is significantly obscured by a huge organ reaching to the ceiling. And because of this, it is impossible to make a coherent picture of the ceiling painting.
Moreover, the organ itself was unavoidable, since due to the renovation work of the church, the rest of the ceiling was covered with a thick protective mesh tarpaulin (pictured above). So when I tried to get a better view of the fresco from a distance with a telephoto lens, the protective tarpaulin covered the painting.
In addition, the lighting conditions were not ideal. In terms of artificial lights, this part of the church was the least illuminated, but natural light flowed in through huge windows on both sides of the organ, which in turn had a very uneven brightness distribution on the surface of the fresco to be photographed. The use of flash inside the church is prohibited.
I will divide the solution of the task on the principle of photography into two parts:
Uniform and colourful illumination of the ceiling of the interior with high ceilings..
Undistorted and uniform digital mapping of ceiling painting.
1. Large amount of continuous light courtesy of NANLITE
NANLITE Forza 500 is an LED studio lamp with remarkable brightness for its size. It was also a great choice for accurate color reproduction, as it has a CRI (color rendering index) of 98 and a TLCI (Television Lighting Consistency Index) of 95. The Bowens-type connection allows the use of various light-forming devices.
The relatively light size, high brightness and color-accurate illumination capability all played a key role in the implementation of the project.
Measured from the gallery floor, the ceiling is about 7-8 meters high. The upper edges of the organ structure (except for the sculpture complex at the top) extend to a height of 5-6 meters, so the light sources had to be at least 4 meters high so that the organ would not block the path of light.
The NANLITE Forza 500's power supply and controls are placed in a separate unit from the luminaire, allowing for a more even weight distribution of the entire structure at this height.
The ceiling was fully illuminated by two Forza 500 lamp placed at an equal distance from the two sides of the organ. The light stand on the right was a lighter design, so I attached it to the ladder I found on site for safety. There are situations where some improvisation may be necessary, and in such cases, efficiency comes before aesthetics. :)
I used a 70 x 100 cm softbox with an internal diffuser as a light modifier. Compared to their size, the light from the NANLITE lamps was distributed uniformly and softly on the curved ceiling..
2. When the third dimension is needed
Unfortunately, what has been written so far has made it clear that the task cannot be accomplished with ordinary photography. So I resorted to a method of three-dimensional scanning called photogrammetry.
PHOTOGRAMMETRY is a technology that allows us to collect spatial information about objects using photos taken from different directions. Thus, with the help of two-dimensional images, it is possible to create three-dimensional models.
Photogrammetry is one of the most cost-effective types of three-dimensional scanning, as you can start learning about the technology with almost any imaging device. Among its disadvantages, however, it is worth mentioning that it cannot be expected to be fully dimensionally accurate, and it is not or only partially suitable for 3D digitization of objects containing reflective surfaces.
Since it took a lot of pictures, I planned to use DJI's Osmo Pocket camera to speed up the process. Its size, weight and built-in gimbal would have made it possible to take the necessary photos quickly and efficiently in high places. However, despite the 1" sensor upgrade, the still image resolution of the latest Pocket 3 camera was only 9MP, which made me stick with DSLR cameras.
Not only did high positions be required for the lamps, but the camera system also had to be as close to the ceiling as possible. I was helped with this by my self-designed carbon fiber high tripod, which provided a stable attachment for the photography equipment even at a height of six meters.
Technical details:
Camera: Nikon D5100 (16MP)
Lens: Tamron 17-35mm f/2,8-4 Di OSD
Focal Length: 17mm (Crop: 25,5mm)
Aperture: f/5.6
Shutter Speed: 1/80s
ISO: 640
White balance: best suited to the lighting conditions of the environment, but definitely not Auto!
Remote control: qDslrDashboard App
The essence of photogrammetry is to take as many images as possible of the object or surface to be scanned at the same focal length, from as many angles and distances as possible. By moving the tripod horizontally and vertically, as well as rotating its sections, almost any camera direction could be realized. An automatic system (MIOPS Capsule Pro) was needed only to tilt the camera, because with a manual head the process would have taken much longer.
A total of 188 photos were taken to cover the entire ceiling. Fewer pictures would have been enough if we had a better view of the fresco as a whole, and if the upper part of the organ (supporting beams and statues) had not covered the painting itself in many pictures, even at this height.
After the images were taken, a photogrammetry software was needed, which generated the 3D model with the help of the photos. There is a really wide selection of these softwares from both free and paid versions. In this case, I used a program called Agisoft PhotoScan (now called Agisoft Metashape):
Thanks to the many photos, a really beautiful and detailed end result was obtained. The blue squares in the space shown in the image above show the camera position of the photos in the 3D space. Since I only needed the ceiling, I removed all other distracting parts from the model.
After exporting the three-dimensional model with high-resolution textures, a 3D software was needed to create the final 2D version of the ceiling fresco. In fact, the free program called Blender is enough for this, since our model has been digitized in a lighted form.
One of the biggest advantages of a 3D model of an arched ceiling surface over plain photography is that, in addition to perspective mapping, orthogonal (perpendicular) projection is also possible. Thanks to this, a distortion-free reproduction of the ceiling fresco could be made. The following image shows the raw version rendered from the 3D program.
The raw image above is not only underexposed, but also shows the shadows cast by the supporting beams on top of the organ and the statues reaching to the ceiling. The final form of the photo was obtained through a significant amount of post-production.
The resolution of the final image was 9435 x 5328 pixels (50MP). Amply sufficient for publication in any book of any size.
Thank you for the trust and opportunity of the Salzburg Museum and for the devoted help and patience of the employees of the Benedictine Church in Győr.
Also thank you to Tripont Foto Video Kft., for contributing two NANLITE Forza 500 lights to this special project. If you also need powerful continuous LED lamps, you can even rent them at the link below:
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