卡罗法，1835年，英国人塔尔博特(Henry Fox Talbot)以纸为片基并使用食盐水定影成功，取名卡罗法。此方法得到的影像是负相，称为 Calotype or talbotype「卡罗版」，可以复制为正相的照片。
You need 两把软刷 two soft brushes, several vials, 白色水彩纸 white watercolor paper , 硝酸银 silver nitrate, 碘化钾 potassium iodide, 乙酸 acetic acid (33%) and 没食子酸 gallic acid (100%) a warm plate and a copying frame that consists of a wood or metal board covered by a piece of glass.
卡罗法所需材料及工艺
Two or Three Shallow Dishes, for holding distilled water, iodide, potassium, &c.–the same water never being used for two different operations.
White Bibulous Paper.Photogenic Camera–Fig. 9.
Pressure Frame–Fig 29.
Paper, of the very best quality–directions for the choice of which have been already given.
A Screen of Yellow Glass.
Camels’ or Badgers’ hair Brushes:–A seperate one being kept for each wash and solution, and which should be thoroughly cleansed immediately after using in distilled water. That used for the gallo-nitrate is soon destroyed, owing to the rapid decomposition of that preparation.
A Graduated Measure.
Three or Four Flat Boards, to which the paper may be fixed with drawing pins.
A Hot Water Drying Apparatus, for drying the paper will also be found useful.