Archived posting to the Leica Users Group, 1999/11/09
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Erwin, You postulate an interesting point, but if an image is good it does not matter if it were shot with a Brownie or a Leica. Shooting with the Leica of course will result in a sharper picture, but a good image is a good image. I know I have said this before, but a famous photographer by the name of Alfred Eisenstaedt was once asked about how he tested lenses. He replied, "I take pictures with them; if I like the results, I keep them." Lens tests only serve the audience interested in them and do not improve the content of the image. Peter K - -----Original Message----- From: Erwin Puts [mailto:imxputs@knoware.nl] Sent: Tuesday, November 09, 1999 2:03 AM To: leica-users@mejac.palo-alto.ca.us Cc: leica@topica.com Subject: [Leica] artistic intention and lens performance The argument that one does not need to be concerned with or interested in lens quality when one makes photographs with a purely artistic intent is a bit shaky. There are two implications here. One says that if you cannot see any difference, it is of no importance. And the other is that scientific lens testing is irrelevant for practical photography. Let us first give some definitions. What is meant by 'scientific' lens testing. We all know that most lenses reproduce a three dimensional object on a flat plane of some recording medium (emulsion or CCD). This reproduction is not accurate due to aberrations. So every image projected by a lens will be degraded when compared to the original. This level of degradation can be measured by several methods and when put in a mathematical manner, can be evaluated in a scientific way. Scientific here just means that there are some theoretical notions which are expressed numerically and can be rationally discussed. The image degradation is theoretically and empirically defined as a number of optical aberrations, which can be identified separately. (coma, distortion, chromatic shift etc). So it is possible to study any optical system in the way it will record an image over its full image field and a number of distances from object to film plane. And of course for several apertures as the aperture influences the level of degradation. In the past astronomers designed lenses purely by trial and error and got good results. Since we have an optical theory (thanks to Seidel and Petzval) we have progressed rapidly. Now we can describe any lens in its level of aberration content and this description tells us quite correctly how much image degradation we may expect, including aspects as flare. The artistic image starts with a random pattern of color patches, grey tones and luminance differences. Strange as it may seem: any photograph consists of a pattern of luminance differences, and that is all. Our senses make sense of such a pattern, and such a pattern evokes emotions, conveys meaning and records information. Here we have the realm of cognitive psychology and in photography this is codified in the so-called 'language of photography'. Numerous books have as subject the question how to look at a photograph and see its meaning and beauty. In my view it is evident that the luminance pattern is influenced by the recording capacity of the lens (or its aberration content). By inference the aberration content will influence the recording of this pattern and so its meaning will be different depending on the level of image degradation. There is thus a strong relationship between the optical quality of a lens and its projected image on film: the luminance distribution. If we see this relationship and will acknowledge its importance is a different story. That we do not see it, does not mean that it does not exist! That is a classical fallacy. So lens quality and quality differences are of the utmost importance to anyone who wishes to record information and by doing this in a manner that evokes a human response (s)he needs to know the relationship between image quality and the meaning of a photograph. It is evidently true that you may wish to ignore this. A pinhole camera works without a lens and gives fine imagery. The justified attention to the sharpness/unsharpness borderline implies a clear relationship between image quality and meaning. This deserves further discussion, not by denying the scientific approach but by incorporating it in the artistic way of photography. Erwin