A run-down watch is still a watch and can be rewound. An old watch, by contrast, becomes so worn and unreliable that it eventually is not worth mending. (New Concept English, Book 4, L. 37)
[原译]手表停了还是手表,还能重新上紧发条。打个比方,一只旧表磨损得非常厉害,变得非常不可靠,以致最后连修也不值得了。(中译本)
by contrast 是指“打个比方”吗？
by contrast with, 可以译为“与……比较起来”“与……相对照”。例如：
By contrast with our previous failures, our minor success this time may even be considered significant.
跟以往几次失败比较起来,我们这次小小的胜利甚至可以说是意义重大的。
by contrast 单独使用时, 是一个起连接作用的词项, 韩礼德(Halliday) 和哈桑(Hasan) 认为它是表“反意”的连接词项，一般可译为“与此不同”“与此相反”“相反”“相比之下”“对比起来”“而”。例如：
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Secondly, the native speaker's comment probably owes a good deal to the fact that he does not feel the rules of his own language — rules that he has acquired unconsciously — to be at all constraining; and if ever he happens to be called on to explain one such rule to a foreigner he has very great difficulty. By contrast, the grammatical rules he learns for a foreign language seem much more rigid and they also seem clearer because they have been actually spelled out to him in the learning process. (GCE) 其次, 这个讲本族语的人讲这句话, 可能在很大程度上是由于他根本不觉得本族语有什么规则在约束他(其实他已不自觉地掌握了这些规则)。但如果有一天有人请他给外国人讲解这样一条语法规则的话, 他会觉得非常困难。与此相反, 他所学习的某种外国语的语法规则, 倒显得严谨得多, 也显得更为清楚, 这是因为在学习的过程中, 这些规则实际上已有人一点一滴地给他讲解过了。
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By contrast, even the most modern aircraft look clumsy and slow. 相比之下，甚至最现代化的飞机也显得又笨又慢。
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Today, by contrast, the area is a lively and colorful fruit, vegetable, and flower market. 与从前不同，这个地区今天已成为一个繁华的、丰富多彩的水果、蔬菜和鲜花市场。