EVALUATION OF A DIGITAL NON METRIC CAMERA (CANON D30) FOR THE 
PHOTOGRAMMETRIC RECORDING OF HISTORICAL BUILDINGS 
J. Cardenal* ', E.. Mata?, P. Castro“, J. Delgado', M. A. Hernandez, J.L. Perez?, M. Ramos, M. Torres“ 
“ Dept. Ingenieria Cartografica, Geodesica y Fotogrametria. Escuela Politecnica Superior. Universidad de Jaen. 23071- 
Jaen (Spain) — (jcardena, emata, pjcastro, jdelgado, acaro, jlperez, mtorres)@ujaen.es 
KEY WORDS: Digital Camera, Non-Metric, Calibration , Archaeology, Architecture, Cultural Heritage, Low Cost, Close Range 
ABSTRACT: 
This paper is about the evaluation of a digital non-metric reflex camera (Canon D30) for low cost applications in archaeology, 
architecture and cultural heritage. At present digital cameras of different geometric qualities are being routinely used for this 
purposes. The Canon D30 digital camera is a professional camera with a CMOS sensor of 3.2 Mp. Although camera resolution is 
relatively low, compared with more recent amateur cameras, the sensor is slightly smaller in size than conventional 35 mm film 
format. The focal length/angle of view conversion factor is approximately 1.6x compared to full frame 35 mm film format. This 
property makes very interesting the use of this camera in cultural heritage photogrammetric applications, where both accuracy and 
final image quality are quite important. The camera internal geometry has been solved by means of self calibration with own 
developed software. First self calibration was made at laboratory using digital target measurement at subpixel accuracy. Proportional 
accuracies with this method were between 1:20.000 and 1:30.000. But additional self calibrations where carried out with field 
control points. In this case, accuracy reached was poorest because images were manually measured on natural points, but it was for 
normal architectural/archaeological applications enough. As main drawback of this camera we can point out the low sensor 
resolution. So when camera/object distance increases or high oblique photographs are employed the image quality of the final 
product reduces considerably. 
I. INTRODUCTION 
Last decade has seen an extensive use of digital non metric 
compact cameras for use in low cost applications in 
archaeology, architecture and cultural heritage. The important 
rise in image resolution, the dropping prices, present facilities 
in storing/transferring images files and easy direct image 
acquisition (without digitising films or paper prints) are the 
main responsible for the attractive use of this instrumentation. 
Also the use of low cost digital photogrammetric systems (both 
stereoscopic and convergent stations, such as, for example, 
DVP®, ShapeCapture®, Photomodeler®, 3D Mapper®) has 
contributed to the use of these “off the shelf” cameras among 
photogrammetrist and non photogrammetrist. 
These cameras have been routinely used for low cost 
applications, but only in cases where accuracy was not critical. 
Several reasons explain the loss of accuracy when these 
cameras are used. These cameras are designed mainly for the 
amateur market and not for photogrammetric purposes. Lenses 
are small and, in general, not of very good geometrical and 
optical qualities. Also usually they are auto focus zoom lenses 
(so high inner instability should be expected). Sensors (both 
CCD and CMOS types are usual) are much reduced in size than 
those of high quality digital cameras and than 35 mm film 
cameras. Sensor size is a very important drawback in the use of 
these compact cameras with metric purposes. Usually sensor 
sizes vary from 1/2.7” to 2/3". Even in the case of a high 
resolution sensor (some present “off the shelf” compact 
cameras reach 8 Mp) metric precision is not guaranteed. 
Besides, once cameras have been calibrated, inner parameters 
are not stables, so important space reconstruction errors can 
occur. Anyway, adequately calibrated, some of these cameras 
can reach subpixel accuracy (at least at laboratory conditions) 
and they can be suitable for archaeological applications 
(Ogleby et al, 1999). 
In this paper, a digital single lens reflex (SLR) camera, Canon 
D30 (Figure 1), is analysed for its use in archaeology and 
architecture. But the scope of this analysis goes to explore the 
metric applications not only in low accuracy and fast 
applications but also in medium precision works with 
conventional data reduction instrumentation (stereo plotters). 
  
Figure 1. Canon EOS D30 SLR digital camera with battery grip 
2. THE CANON EOS D30 CAMERA 
The image pick-up device used in the EOS D30 is a 3.25 
million pixels complementary metal oxide semiconductor 
(CMOS) sensor with noise reduction functions. Total pixels are 
2226 x 1460, but effective pixels are 2160 x 1440. The sensor 
size is 15.1 x 22.7 mm (aspect ratio 2:3), so it is slightly smaller 
than conventional 35 mm film camera format (Figure 2). Files 
can be recorded in RAW and JPEG (with two compression 
levels) formats. The recording media is a CF (Compact Flash) 
card, type I or II. The sensitivity is equivalent to ISO 100-1600. 
The camera has the usual features (manual and several 
automatic exposition modes, different metering systems, 
    
  
   
   
   
  
    
   
   
  
    
  
  
  
  
   
    
    
   
   
     
    
   
    
    
    
    
    
     
  
   
   
   
   
    
   
   
   
    
    
   
    
   
      
    
   
    
      
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