底片加厚

增高底片（或正片）銀影密度的方法.攝影中由於曝光或顯影不足，銀影密度全部都小於正常值，或陰影部分密度太小，這樣的底片需要用加厚的方法提高底片的密度，方能印放出高質量的照片.常用的加厚方法有三種：（1）比例加厚.根據銀影密度大小，按比例增加，即密度大處增加得多，密度小處增加得少，因此可以提高影像的反差，通常用以重鉻酸鉀為主的加厚劑.（2）超比例加厚.即對銀影密度大處增加得特別多，密度小處沒有什麼影響，因此能極強地提高影像的反差，通常用硝酸銀和氰化鉀或氰化鈉為主的加厚劑.（3）低比例加厚.對銀影密度小處稍能增加厚度，對密度大處不增加，因此能調節影像的反差，通常用硝酸銀和亞硫酸鈉為主的加厚劑.加厚須反覆多次進行，方能得到預期效果.加厚處理的時間長短不一樣，可以在一定程度上獲得不同的加厚效果.加厚還可以在底片的局部進行，一般採用“塗紅”的方法，即用羊毫毛筆蘸著紅色顏料液在需要加厚的地方反覆塗抹，達到理想效果為止. Higher negatives (or positives) Silver Shadow density method. Photography or imaging due to lack of exposure, silver and shadow density, all smaller than normal, or the shaded area density is too small, such a film need to usethickfilm of means to enhance the density of before being released high-quality photo printing. common thickening in three ways: (1) the proportion of thickening. According to Silver Shadow density of the size increased in proportion, that is, to add the density is much smaller at the density increases slightly, So can improve the image contrast, typically used consisting mainly of thickening agent potassium dichromate. (2) the proportion of super-thick. that the right to add the Silver Shadow density was particularly high density, small Department has very little effect, so they can highly improved image contrast, usually silver nitrate and potassium cyanide or sodium cyanide based thickening agent. (3) low percentage of thickening. For Silver Shadow density can increase the thickness of a little office on the density at not increase, it can adjust the image contrast, usually silver nitrate and sodium sulfite-based thickening agent. thickento berepeated numerous times, can only get the desired effect. thicken not the same as the length of processing time can to some extent get a different effect on thickening. thickening can also be carried out in the local film, generally adopt the "painted red" approach, that is, a brush dipped in red paint with the Yang Hao liquid where needed thicker smear repeated to achieve the desired result so far.

底片加厚

基本介紹

相關詞條

熱門詞條