within reason

To an extent which is reasonable; not beyond what is reasonable.

Japanese Meaning

合理的な範囲内で / 妥当な限界内で / 無理のない範囲で

You can borrow my camera within reason, but please return it clean and on time.

カメラは妥当な範囲で借りても構いませんが、きれいにして時間どおりに返してください。

Sense（1）

To an extent which is reasonable; not beyond what is reasonable.