The second case study for the NUIM-AFF621: Remaking the Physical – 3D recording assignment involved the capture of a statue in the outdoors using a digital camera. Thereafter, it entailed the processing of the photographs using photogrammetry software and online tools to produce a 3D model. This post will discuss the background of the object and the capturing phase for this case study.
Initially, I tried to capture a statue in a local grave yard, however, this was not very convenient due to the amount of people moving around in the background. Also, I was not at ease having to stand on graves to rotate around the object (as people were watching me) and I soon abandoned the effort.
My experience in the first case study had left me fully conscious of the necessity to shoot the best photographs possible to better enable the processing software to produce an accurate 3D model. I was determined to make a better 3D model this time around, therefore, I chose to photograph a statue in my mother’s garden to allow me to concentrate on the capturing with few distractions. The statue was bought 25 years ago from a market stall, and there is no knowledge of the creator, nonetheless, it is of great sentimental value to my mother as it was the first outdoor statue she bought when she moved to that house.
Unlike the previous case study where the artefact was placed on a turntable and photographed in rotation by moving the turntable, this case study involved taking photographs whilst moving around the object. Best practice for capturing in the outdoors, for the purpose of photogrammetry, indicates the avoidance of direct sunlight, environments with casting shadows, and ideally capturing is best done on an overcast day (Recap Product News). The day I chose for the capturing started off cloudy, but soon after there were sunny spells. Therefore, I had to keep stopping and starting according the sun, as when the sun came out the shadows were quite noticeable, as shown below.
The capturing was done using a Fuji Film Finepix AX510 (14 megapixel). This camera offers various shooting mode options, and while the camera offers a programme mode to manually alter the ISO, exposure time and white balance, I opted for ‘Scene Recognition’ mode with no flash. In this mode the camera adjusts itself to the scene according to the conditions. I had no tripod for this camera, therefore, it was hand-held throughout the capturing stage.
Excerpted from the Fuji Film Finepix AX510 Manual
I planned for four levels of photographs in rotation, one sitting on the ground, another level on my knees, then from the standing position, and finally standing directly over the top of the statue. I tried to keep the rotating angles in line with the ‘correct’ image below.
If the sun came out during the photography of one level, I stopped and waited until the sun went behind a cloud. I then started to photograph that level again from the beginning, rather than try to continue from where I had left off. I felt that this would maintain a better consistency in the angles. When viewing the photographs later on, via the laptop, the camera properties indicated that the aperture and exposure time (shutter speed) was corrected automatically by the camera for different photographs, while the ISO was maintained at 100 and the resolution was 4288 x 3216.
Overall there was a good consistency between photographs, and I felt no need to rectify the photographs for brightness and contrast. In sum, there were 170 photographs taken, but I deleted some of these as they were uncompleted shoots of a level (i.e. when the sun came out), so I had 124 photographs going forward to the processing stage.
In the next post, the processing stage will be discussed via the options of Agisoft PhotoScan Professional and 123D Catch (Autodesk).
- Autodesk ReCap Product News. “What Makes Photos Good for Photogrammetry?” ReCap Product News. Web. 9 Apr. 2015. <http://www.recapproduct.com/blog/2014/11/what-makes-photos-good-for-photogrammetry.html>