|/// slashCAM - Camcorder tests and ratings
In our tests and the comparison database we use thirteen categories to rate the camcorders. But since we consider some features more important than others, not all categories have same weight when the total test score is calculated:
Lowlight -- 10%
Resolution -- 8%
Color performance -- 8%
subj. picture impression -- 10%
Optical Zoom -- 5%
Wide Angle -- 10%
Configuration / image -- 10%
Configuration / sound -- 8%
Handling -- 10%
Portability -- 5%
Photo function -- 2%
Optics -- 8%
Dynamics -- 6%
This means that the photo function grade only has a 2% impact on our final grade, whereas the low light grade accounts for 10%.
So how do we decide on the grades in each category?
In our opinion low light performance is one of the most important critera when judging the image quality of a camcorder. To test this we record our test setup in automatic mode at 12 lux and check the resulting image for color reproduction, sharpness and noise. These test images can be found in full resolution in our database, for those who want to draw their own conclusions.
To define the luma resolution we record the well known ISO12233 test chart. (These pictures are also in our database.) Here one can see how many lines a comcorder can depict, and how much artificial sharpening is added (contour). We think it is unfair to just count the visible lines and give a specific number (as others often do in their tests) since the contour always influences this value, and because it never is obvious where the grey threshold is to be set. Often a picture with strong contour will receive a high line count but look bad and over-sharpened to the naked eye. So instead the subjective sharpness impression incl. contour will decide our rating, along with the eventual possibility to adjust / reduce the contour settings.
The iso chart can only measure the luma resolution, which by now often is very good even on cheaper camera models. But for a natural image impression the chroma resolution is important as well, even if the eye mostly cannot perceive small differences. When analysing the chroma channels though, the differences which make for either clear or soft colors can easily be detected. And although (H)DV with its 4:2:0 chroma subsampling already has reduced color reproduction, there can be great differences between camcorders.
By the way, a good color reproduction is also very important for chroma-keying.
When rating the optics we primarily look for two things: chromatic aberration and distorsion. Chromatic aberration means that the color layers are not positioned exactly over each other so that colored fringes can be seen on depicted objects. In strongly distorted images what should be straight gets bent -- especially when filming in wide angle lines can get extremely curved at the image borders. We check the pincushion distorsion with the lens in maximum wide angle.
This includes all properties which influence the way light is transformed in video signals (noise, over amplification, gamma (entry dynamics) and the resulting value span (exit dynamics).
Subjective image impression
Resolution and compression are important factors, but in the end the visual result counts -- and that is not always accounted for in the measurements. So this is where we trust our eyes: is the image as a whole coherent, or not?
Optical zoom and wide angle
This should be self-explanatory -- the camera is rated in terms of max. optical zoom and wide angle.
Configuration / image
Here we currently check 37 features in terms of availability and quality, for example viewfinder, display, focus ring, zebra function, ND-filter etc.
Configuration / sound
Here we currently check 14 features in terms of availability and quality -- important are for example microphone jack, headphone jack, manual audio level control.
Here it gets subjective again: is the menue navigation logical? Are important buttons and functions easy to reach? Did we find our way fast with the camera or was some hair-tearing involved?
The size and weight decides this grade. For some uses a very compact camcorder can be very useful.
This describes to what extent the camcorder can substitute a low budget digital still camera.