Не будь освещения, экспозиция была бы другой.

In this sentence, не будь is an idiomatic conditional expression, not a real command.

Не будь X, Y... means roughly:

• if there were no X
• were it not for X
• had there not been X

So:

Не будь освещения, экспозиция была бы другой.
= If there were no lighting, the exposure would be different.

Even though будь is formally the imperative of быть, in this pattern it functions more like a fixed literary shorthand for если бы не было.

Because this construction expresses the absence of something, and Russian normally uses the genitive with negated existence.

Compare:

• Есть свет. = There is light.
• Нет света. = There is no light.

Similarly:

• Если бы не было освещения... = If there were no lighting...
• Не будь освещения... = Were there no lighting...

So освещения is genitive because the idea is essentially the absence of lighting.

That is how Russian normally forms the conditional mood.

Russian uses:

• past tense form
• plus бы / б

to mean would.

So:

• была бы = would be
• сделал бы = would do / would have done
• помогла бы = would help

In this sentence:

• экспозиция была бы другой = the exposure would be different

This is a hypothetical, unreal situation, so the conditional is exactly what Russian needs here.

Because не будь is already a special fixed conditional formula.

A fuller, more explicit version would be:

• Если бы не было освещения, экспозиция была бы другой.

Here the first clause contains бы because it uses the normal если бы pattern.

But in the shorter literary version:

• Не будь освещения, экспозиция была бы другой.

the expression не будь itself carries that hypothetical meaning, so you do not add another бы there.

Because другой here is in the instrumental case, which is very common for a predicate after быть in the past, future, or conditional.

So:

• она была учителем = she was a teacher
• он будет врачом = he will be a doctor
• экспозиция была бы другой = the exposure would be different

With predicate adjectives, Russian often prefers the instrumental when describing what something was/will be/would be.

You may sometimes see nominative in other contexts, but here другой is the most natural standard choice.

Yes. The most direct version is:

Если бы не было освещения, экспозиция была бы другой.

This means the same thing and is easier for learners to parse.

So you can think of:

• Не будь освещения...

as a more compact, more literary equivalent of:

• Если бы не было освещения...

It is understandable and not rare, but it sounds more bookish, literary, or elevated than everyday speech.

In ordinary conversation, many speakers would more naturally say:

• Если бы не было освещения...
• Если бы не свет...

So не будь X is useful to know, but it is not the most neutral colloquial way to express this idea.

Освещение usually means:

• lighting
• illumination
• the lighting setup / light conditions

It is a bit more technical or contextual than simply свет.

In a photography context, освещение is especially natural because it refers to the lighting affecting the shot. So with экспозиция it fits very well.

Compare:

• свет = light in a broad sense
• освещение = lighting / illumination conditions

Because the first part is a separate conditional clause, and Russian separates it from the main clause with a comma.

Structure:

• Не будь освещения, = if there were no lighting,
• экспозиция была бы другой. = the exposure would be different.

This is similar to English punctuation in sentences like:

• If there were no lighting, the exposure would be different.

Yes. Russian word order is flexible, so you could also say:

Экспозиция была бы другой, не будь освещения.

That means the same thing: The exposure would be different if there were no lighting.

The original order puts the condition first, which is very natural because it sets up the hypothetical situation before giving the result.

Yes. The pattern is fairly productive, especially in written or formal style:

• Не будь дождя, мы бы пошли гулять.
  = If it weren’t for the rain, we would go for a walk.

• Не будь его помощи, я бы не справился.
  = If it weren’t for his help, I wouldn’t have managed.

• Не будь этой ошибки, всё было бы иначе.
  = Were it not for this mistake, everything would be different.

So the model is:

Не будь + genitive noun, main clause in the conditional

That is a very useful pattern to recognize.