3 Publications by Joseph Petzval, 1857–58

Professor Joseph Petzval, founder of the calculation for photo lenses, text in German. 1) "Report on Optical Investigations" (from the March 1857 issue of the "Academy of Sciences", Vol. XXIV, p. 50, printed separately), Vienna 1857, with the 2nd and 3rd continuations, 58 pages in total, announced at the meeting on March 12, 1857. – 2) "Report on Dioptric Investigations" (from the October 1857 issue of the "Academy of Sciences", Vol. XXVI, p. 32, printed separately), Vienna 1857, 60 pages, presented at the meeting on July 23, 1857, a lecture for photographers who want to learn what a lens is. – And: 3) "On the New Landscape Lens as a Telescope" (from the XXXI. Volume, No. 18 of the "Academy of Sciences", printed separately, Vienna 1858, 15 pages. Quote: "I do not believe that since the first beginnings of practical optics any article has ever provoked such a violent, rebellious movement among optical artists as this lens. It had barely been published when it had already found a significant number of imitators, and the imitators had found more imitators... the army of imitators has already got into a fight in the various European journals, and one says as many spiteful things about the other as he can find... yet it hardly befits the scientific man to pour out harsh criticism... rather, it falls on him to protect the interests of science in this colorful ecstasy..." – Joseph Petzval explains to users of this lens in great detail how to adjust the sharp focus to one with an improved effect of depth by changing the distance. Quote: "… every photographic artist who has diligently studied the new lens and learned its peculiarities will be able to obtain as much depth of focus as he needs by changing the distance." – Two centuries later, these three treatises are still relevant for today’s optical engineers, especially since the freshness and directness of Petzval’s language illuminates the effects of ignorance and prejudice on people’s minds. Historically valuable resources.

布雷克拍品等级是为了方便竞买人判断拍卖品的成色而设置的。布雷克等级用1到6级来标注外观和功能的成色，(从非常好到非常差)。 在目录图册里用括号里的2个数字来表示，前一个数字表示外观成色的级别，后一个数字表示功能成色的级别。如(3/2)表示外观成色是3(满意的)，功能成色2(好)。 成色 定义参照下列标准： 1 - 非常好 (未使用过，没有使用痕迹) 2 - 好 (新，极少的使用痕迹) 3 - 满意的 (普通的使用痕迹) 4 - 及格的 (明显的使用痕迹，某个非主要部件是后配的) 5 - 有缺陷的 (极明显的使用痕迹, 某个主要部件是后配的，功能上有缺陷，需要修理) 6 - 非常差 (严重破损, 缺少重要部件)