关于黑白底片出现圆晕的问题

最近比较困扰我的是冲洗出来的底片有不同程度的圆晕，跟各位朋友商讨原因未果，故发上来请教。

先把已知的所有线索列出：
1、自配D76 1:1药水，分析纯水开药；
2、一开始怀疑是空气铃，但冲片过程已经特别注意拍打罐身；
3、原以为底片拍摄前置于冰箱内受潮，但后来买了不同批号的新胶卷而且没有置于冰箱，情况依然出现；
4、早前的分装卷也出现过，当时以为是分装卷不洁，但现在用的是原装的Tri-X；
5、同一卷里面有的有，有的很正常，而且未必是连续出现的；但严重的一次是全部都有；
6、同一晚同时冲的几卷，同样的药水和设备，公元100没事（冲了很多都没事），120的APX100没事，delta100有轻微，Tri-X的那卷个别比较严重（见附图），而且经常是Tri-X有事；
7、也曾怀疑是静电所致，但无论手动相机和自动相机拍摄依然有此情况。

同一卷的第4张和第28张比较严重的，其余大部分都基本正常：

第14张，留意右下角。

另一个朋友的片子，胶卷不祥，只有轻微的圆晕（小孩头部左上角）

从你扫描的图片上看，怎么看都像是空气铃，你用的什么显影罐？试过换一个罐子或者轴芯了吗？或者你在灌入药液时，把显影罐稍微倾斜一些，然后以均匀的速度倒入药液，不必太慢，整个过程在10秒内完成即可，这样做可以让空气尽量少的带入罐内，然后在每次搅动后都记得在桌面上拍打一下罐子，防止搅动药液时产生的气泡。

还有：如果你用大号的罐子，每次只冲一卷135的话，要把不用的轴芯都装进去，并且药量仍要使用显影罐的最大容量，这样做的目的就是要让罐内的空气尽量排出，避免发生显影不匀。

[[i] 本帖最后由 法拉夏利 于 2007-7-7 17:58 编辑 [/i]]

[quote]原帖由 [i]法拉夏利[/i] 于 2007-7-7 17:44 发表 [url=http://leica.org.cn/bbs/redirect.php?goto=findpost&pid=24876&ptid=2369][img]http://leica.org.cn/bbs/images/common/back.gif[/img][/url]
从你扫描的图片上看，怎么看都像是空气铃，[/quote]

严重同意。

感谢法拉兄弟回答！空气铃的说法我们也探讨过，也特别留意拍打罐身，但不能解释为何同一人、同样的冲洗手法、同一时间段内（接近半年）所有的公元片没有出现圆晕。

碰巧的是，刚才一个喜欢寻根问底的朋友给我挂电话，说在一本黑白摄影的书里面找到一说法，大概的意思是[b]由于相机和胶卷积累了电荷，由相机或近处物体向胶片放电而形成环状牛顿环的黑心漫射状斑点。[/b]

这个说法比较能合理解释为何公元的片子没有出现圆晕，估计极可能是公元和Tri-X的片基有很大的不同，而对电荷积累程度各异。

另外，我基本把Tri-X装进T3拍摄，根据上述线索，我特意的回想自己拍摄时操作相机的步骤。发现自己经常频繁而快速的从皮套里插拔相机，而那个皮套内部都是绒毛，加上T3的金属外壳，极其容易摩擦而引起静电，这也能解释为何总是我的Tri-X卷出现圆晕。

我刚用CM+HP5拍了一卷，今晚用同样的药水和显影罐冲，看看是否还有上述情况。

下一阶段，我会换一个不产生静电的相机套，另外装卷前清洁一下相机内部，甚至特意放一下电，看看能否有改善。

[[i] 本帖最后由 阿祖 于 2007-7-7 22:02 编辑 [/i]]

关于静电对胶片的影响，柯达公司有如下的解释，你可以参考一下，期待你的测试结果 :) 不过我仍然坚持最初的观点，因为从你照片拍摄的地点和气候看，不应该产生如此强烈的静电。

Static Marks

WHAT ARE THEY?
Two types occur; one is almost circular with very fuzzy edges, the other consists of short, fuzzy lines. Both are microscopic and will be picked up only by AOI. These marks are extremely rare.

WHEN CAN THESE OCCUR?
They can happen at any time during film handling prior to processing, but most likely during removal of film from packaging or loading of the plotter.

WHAT CAUSES THEM?
An electrostatic discharge acts like light, causing silver halide grains to devel-op into metallic silver during processing.

HOW CAN THEY BE PREVENTED?
Today’s films have anti-static protection that helps to prevent such discharges. Customers should follow the plotter manufacturer’s recommendations for operating humidity (usually 50 to 60% RH).

Typical static marks on film
[attach]10960[/attach]

[[i] 本帖最后由 法拉夏利 于 2007-7-8 03:31 编辑 [/i]]

下面是KODAK关于空气铃的文档摘录，供参考。

AIR BELLS

When air bells or bubbles of air form on film surfaces during processing, they produce circular spots on the film. These spots may have distinct edges or relatively diffuse edges. They may be higher or lower in density than the surrounding areas. Patterns vary from isolated spots to clusters where a heavy concentration of air bells or foam formed.

How Do Air Bells Affect Photographic Materials?
Air bubbles adhering to film surfaces prevent processing solutions from penetrating the emulsion. If this occurs in the developer, the result will be a circular spot that shows lack of development. Air bells in other solutions may produce spots of overdevelopment where the developer continued to act on the emulsion, or spots may form where incomplete bleaching, fixing, or washing has occurred.

With color materials, the color of the marks depends on the process and at what step in the process the air bells formed.

Why Do Air Bells Form?
Air bubbles may simply cling to film surfaces when you first immerse the film in a processing solution. That's why initial agitation to dislodge bubbles is so important.

Also, any condition that causes bubbles or foam in a processing solution can help to form air bells. All of the following factors can contribute to air-bell problems:

overagitation
equipment that draws air into solutions
use of solutions too soon after mixing
temperature changes in solutions
insufficient filling of closed processing tanks
incorrect filling of rotary-tube processors
improper distribution or leaks in gaseous-burst agitation systems
freeing up of dissolved air when cold incoming water warms to room temperature or is heated to provide hot water

How Do You Prevent Air Bells?
The most important factor is proper initial agitation. In batch systems, rap the reels or racks against the side of the tank to dislodge air bells carried in on the film. Agitating too vigorously causes bubbles to form. Agitating for too long a time can produce mottling.

In automatic processing systems, properly maintain the agitation system. In closed tanks and rotary-tube processors, be sure to observe proper filling procedures.

Treat dissolved air in a water supply by installing an aerator on the faucet. An aerator produces large bubbles, which rise to the surface and don't adhere to the film. Allow cold tempered water to stand before using it; this will allow dissolved air to dissipate.

When the water supply is cold, you can minimize air bells by connecting 100 feet of coiled hose between the water supply and the chemical-mixing area or processor. The water will warm up gradually and the freed air will collect at the top of the coils, producing larger bubbles that won't present air-bell problems.

Allow freshly mixed chemicals or chemicals diluted before use to stand for a time so that dissolved air can dissipate.

What About Films Already Affected?
Air bells that are present in the developer produce spots that are a permanent part of the image.

When spots have formed in other solutions or washes, you can reduce or sometimes eliminate them by reprocessing, starting with the solution in which the spots formed.

Air Bells? Or Something Else?
Sometimes chemical splashes can make spots that look like spots from air bells. Air bells are usually round, so irregularities in the shapes of the spots indicate splatter may be the source.

Air bells may be more irregular when they are caused by heavy foam concentrations. However, you can usually see a foam pattern.

Effects of differential drying can also resemble air-bell patterns. Differential-drying spots occur when small drops of water cause areas of film to dry at different rates. This produces a physical deformation of the surface. In this case, wash films immediately to help reduce the effect.

从片子上看,不象是牛顿环,没装片夹时,牛顿环在底片上是看不到的.

很同意法拉斑竹的意见,每次搅动后必须拍打一下,这很关键.

谢谢法拉夏利资料，很详实，回头我认真读几遍。
如果冲洗前预湿胶卷能否减轻空气铃？

对了，那卷CM+HP5一点事都没有，很奇怪吧？
不过现在起码锁定了2个可能的原因：
空气铃和T3+TriX可能引起的静电。

不过这需要一段时间来检验。

我采用的方法一般都是先进行水浴，并稀释药液，延长时间，这样可以用比较频繁的翻动来降低气泡的产生。同时，片基色也可以最大限度地消除。
所以到现在还从来没有遇到过楼主的情况。

回复 #11 阿祖 的帖子

我很注意去除空气铃的动作，幸好至今还未发生过。至于预湿胶卷的动作，我没有详细比较过，无法回答你，不好意思。