ならともかくIf that were the case, it would be another matter
Marks A as a possible exception, then contrasts it with an actual or more problematic B. A does not have to be good; it only has to be a case for which the speaker might make an allowance or give a different judgment.
How the contrast works
The first part, A, establishes a case that might deserve a different answer: a smaller amount, a special person, a more favorable condition, or another understandable exception. The main judgment then falls on B, which is presented as harder to accept, less reasonable, or simply different enough that the allowance for A does not apply.
Exception first, actual case second
In each example, the scale connecting A and B is clear: a short stay versus a long one, or a repairable machine versus one with no available parts.
一泊ならともかく、一週間もホテルに泊まる余裕はない。
One night would be another matter, but I cannot afford to stay at a hotel for a whole week.
AnalyzeA one-night stay is treated as a possible exception; the actual one-week stay is beyond what the speaker can afford.
私たちは、この機械が修理できるならともかく、交換部品も手に入らないのだから、買うべきではない。
If this machine could be repaired, that would be another matter, but since replacement parts are not even available, we should not buy it.
AnalyzeHere A is a hypothetical condition under which the judgment might change.
An exception is not necessarily approval
Do not assume that the speaker approves of A. A may merely be understandable, tolerable, or small enough to overlook. The expression says that A would be a different matter; the speaker's real evaluation is directed at B.
Exception versus setting something aside
With ならともかく, A is a condition that could change the judgment: “if A were the case, that would be another matter.” By contrast, はともかく primarily sets A aside so that the speaker can focus on something else. Replacing one with the other can therefore remove the exception-versus-actual-case logic.
More examples
初心者ならともかく、経験者がこの規則を知らないのは問題だ。
A beginner would be another matter, but it is a problem for an experienced person not to know this rule.
Analyze五分ならともかく、一時間もここで待つことはできません。
Five minutes would be another matter, but I cannot wait here for a whole hour.
Analyze安いならともかく、これだけ高い商品を、商品説明も読まずに買う気にはなれない。
If it were cheap, that would be another matter, but I cannot bring myself to buy such an expensive product without even reading its description.
Analyze静かならともかく、夜中まで音楽が聞こえる部屋では眠れない。
If the room were quiet, that would be another matter, but I cannot sleep in a room where music can be heard until midnight.
Analyze本人が希望するならともかく、周囲が勝手に進路を決めるべきではない。
If that is what the person wants, it would be another matter, but people around them should not decide their future path on their own.
Analyze緊急時ならともかく、通常の業務で個人情報を持ち出すことは認められない。
An emergency would be another matter, but taking personal information off-site during routine work is not permitted.
Analyze一度だけならともかく、同じミスを何度も繰り返すのは困る。
If it happened only once, that would be another matter, but repeatedly making the same mistake is a problem.
Analyze