Some poor quality images in the database

In the previous section we highlighted two problems present in the KTH-TIPS database, namely the cropping and the orange peel - background problems.

A further source of information degradation is problems with the automatic focus of the camera, and this severely limits the value of any image processing/classification result for those images. Scale 1 (subject closest to the camera) was probably chosen to have an insufficient camera-target distance. Furthermore, in an attempt to get patches which were in focus, non-central patches were often selected, implying that the estimate of camera-target distance is inaccurate. Indeed, one should not be too surprised if poor results are obtained with Scale 1.

Table 5 summarises the images with poor focus.

Table 5: Images poorly focused in the KTH-TIPS database.

Material	Scale	Images
Sandpaper	1	All
Crumpled aluminium foil	1	1,2,3, 7,8,9
Styrofoam	1	1,2,3, 7,8,9
Sponge	1	1,2,3, 7,8,9
Corduroy	1	1,2,3, 7,8,9
Linen	1	1,2,3, 7,8,9
Cotton	1	1,2,3,4, 7,8,9
	8	8
	9	1,4,7,8,9
Brown bread	1	1,2,3, 7,8,9
Orange peel	1	All
Cracker B	1	1,2,3, 7,8,9

Further issues are

• perspective effects at some of the closer distances (this is fairly minor);
• minor creases in cloth (linen and cotton) induce spurious edges. On the other hand, real-world samples of cotton and linen can also have creases;
• specularities with orange peel caused by placing the peel in a CD case. This is prominent at Scale 9.