Proceedings of the twelfth International Congress of Photogrammetry: Commissions I and II

Whitcher, Geoffrey H.

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Multivolume work

Persistent identifier:: 832095508

Author:: Müller, Gustav; Kempf, Paul Friedrich Ferdinand

Title:: Photometrische Durchmusterung des nördlichen Himmels, enthaltend alle Sterne der B.D. bis zur Größe 7.5

Year of publication:: 1894

Place of publication:: Leipzig

Identifier (digital):: 832095508

Reihe:: Publicationen des Astrophysikalischen Observatoriums zu Potsdam

Language:: German

Additional Notes:: Erschienen: Theil 1 (1894) - Theil 4 (1907)

Publisher of the original:: In Commission von Wilhelm Engelmann

Document type:: Multivolume work

Volume

Persistent identifier:: 832095974

Author:: Müller, Gustav; Kempf, Paul Friedrich Ferdinand

Title:: Zone + 20 [Grad] bis + 40 [Grad] Declination

Scope:: 465 Seiten

DOI:: 10.14463/GBV:832095974

Year of publication:: 1899

Place of publication:: Leipzig

Identifier (digital):: 832095974

Reihe:: Publicationen des Astrophysikalischen Observatoriums zu Potsdam (13.Band = Nr. 43)

Signature of the source:: Astr. 6500(2)

Language:: German

Publisher of the original:: In Commission von Wilhelm Engelmann

Usage licence:: Public Domain Mark 1.0

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2015

Document type:: Volume

Collection:: Astronomy

Chapter

Title:: Erster Abschnitt. Beobachtungen der Zonen.

Document type:: Multivolume work

Structure type:: Chapter

> 4 main unaltered. The luminance distribution, however, will be modulated according to figure 1. The Modulation Transfer Function shows, how an imaging system—or a component of such a system—alters the modulation of the test pattern. The MTF is the ratio between the modulation of the image and the modulation of the test pattern itself, frequency by frequency, as illustrat- ed in figure 2. For a linear optical system, the Optical Trans- fer Function (OTF) gives the change in modula- tion and phase of the sine wave pattern. For an emulsion, only the change in modulation is utilized, since the phase has commonly no sig- nificance. Accordingly, the name Modulation Transfer Function (MTF) is used. At the development process of a photographic emulsion, certain phenomena, termed adjacency effects, sometimes occur in the image. As the influence of those effects is difficult to separate from the pure MTF at the evaluation, the Work- ing Group has decided to use the name Photo- graphic MTF, in order to avoid confusion with the real MTF, that does not include the adja- cency effects. Concerning the practical applications, the MTF method has one essential advantage that is to be mentioned immediately, i.e. the pos- sibility to cascade the M'TF's of different links in an imaging system and then determine one single MTF for the entire system. In aerial photography, for example, the lens, the film, the image motion, the vibrations and the haze/ turbulence, all of them have their own MTF. Accordingly, these five MTF's can be multiplied by each other, frequency by frequency. The result is one single MTF, which is the MTF of the aerial negative, the basic material for the photogrammetrist and photo interpreter. In Fig. 3 is shown as an example from practical aerial photography, how different MTF’s have been cascaded. The resultant MTF of the aerial nega- tive is indicated as well. 1.2 Previous ISP Activity During the period 1964— 68 the Working Group on Image Quality, headed by G C Brock, to a GEOGRAPHICAL SURVEY OFFICE OF SWEDEN NO A 39 certain extent dealt with problems related to OTF as well as to MTF. For the present MTF Group, the following statements of the 1968 Image Quality Group are of particular interest: Expression of results as modulation versus spatial frequency gives a useful general im- pression of system performance over a range of sizes, as distinct from the limiting size, which is the only information conveyed by resolving power. MTF does not measure image quality, but measures physical characteristics of image- forming devices. In general, ways must be sought for sup- plementing MTF's with descriptions of image quality by methods that take account of the physical qualities of the emulsion and the properties of human vision. MTF relates only to the optical image that is effective during exposure; it takes no account of the factors such as gamma, granularity and human vision that enter into resolving power, and conveys no direct information about the developed photo- graphic image. The full value of MTF's will not be realised without a considerable improvement in the accuracy of present measuring techniques (as distinct from precision). It may not be possible to achieve great ac- curacy in applying MTF’s to the photo- graphic process, because of non-linearities. These six establishments were well justified, except possibly the last one; in that respect the progress has perhaps become a little faster than was expected. However, the measurement of emulsions is the main task of the present MTF Group, and will be thoroughly discussed in this Report.

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