[en] The know-how in the field of solar radiation distribution in forests is important for basic ecological investigations and silvicultural practice. Three methods of solar radiation assessment based on hemispherical canopy photography are compared in the present article: a hemispherical photography by means of a fish-eye lens, a horizontoscope and the ALI-2000 Plant Canopy Analyzer. Experiences, improved methods and a drawing of a horizontoscope stand which was elaborated at the Chair of Silviculture are presented. Fairly good results with some limitations can be achieved with the improved stable horizontoscope in silvicultural work. Hemispherical photography is appropriate for the assessment of light conditions in all stand types and can thus be used in research work. The method has recently been undergoing intensive development. Digitalization of the entire system will speed up standardization. The ALI-2000 instrument is highly suitable for regeneration research in conditions of abundant plant vegetation, in reach sites and modified stands
[sl]
Poznavanje porazdelitve sevanja v gozdu je pomembno za temeljna ekolo{ka prou~evanja in za prakso gojenja gozdov. V ~lanku primerjamo tri metode ocenjevanja son~nega sevanja na osnovi preslikave svoda neba in kro{enj: fotografijo hemisfere z objektivom ''ribje oko'', horizontoskop in LAI-2000 Plant Canopy Analyzer. Prikazujemo izku{nje, izbolj{ave metod ter na~rt za podstavek horizontoskopa, ki smo ga razvili na Katedri za gojenje gozdov. Izbolj{ani stabilni horizontoskop daje, z nekaterimi omejitvami, povsem zadovoljive rezultate za neposredno gojitveno delo. Fotografija hemisfere je primerna za oceno svetlobnih razmer v vseh tipih sestojev in je zato uporabna pri raziskovalnem delu. V zadnjem ~asu se metoda intenzivno razvija. Digitalizacija celotnega sistema bo pospe{ila standardizacijo. Instrument LAI-2000 je posebej primeren za raziskave pomlajevanja v razmerah bujne zeliščne vegetacije na bogatih rastiščih in v spremenjenih sestojihJournal
Research Reports Forest and Wood Science and Technology; ISSN 0351-3114; 
; (no.60); p. 177-210
; (no.60); p. 177-210
[en] Hemispherical photography represents one of the most appropriate methods of estimating averages of solar radiation over extended periods of time. This method is based upon the use of extremely wide-angle fisheye lenses, which produce large projection distortion. To correctly interpret hemispherical photography we have to know the projection characteristics of the fisheye lens in combination with a camera body. This can be achieved through lens calibration. The first part of the article explains in detail the calibration method for fisheye lenses which are used to assess the solar radiation in forest ecology research. In the second part the results of calibration for fisheye lens Sigma 8 mm, f/4 (MF, N) are presented. The lens was used on a Nikon F50 camera body
Journal
Research reports forest and wood science and technology; ISSN 0351-3114; ; (no.61); p. 5-25
; (no.61); p. 5-25