Bevegelsesuskarpheten øker med lang lukkertid.

Because Norwegian usually writes compound nouns as one word.

This word can be broken down like this:

• bevegelse = movement
• linking -s-
• uskarphet = unsharpness / blur
• -en = the definite singular ending

So bevegelsesuskarpheten is literally something like the movement-blur, which in natural English is the motion blur.

This is very normal in Norwegian. Where English often uses separate words, Norwegian often combines them:

• kamerahus
• bildekvalitet
• lukkertid

That -s- is a linking sound/letter used in many Norwegian compounds. It does not mean possession here.

So this is not like English movement’s blur. It is just the normal way some compounds are formed.

You will see this in many words, for example:

• arbeidsdag = workday
• livsglede = joy of life
• bevegelsesuskarphet = motion blur

Unfortunately, there is not always a simple rule for when the linking -s- appears, so learners often just need to get used to common compounds one by one.

The ending -en marks the noun as definite singular in Bokmål.

So:

• bevegelsesuskarphet = motion blur
• bevegelsesuskarpheten = the motion blur

In this sentence, the speaker is talking about the phenomenon as a specific effect being discussed, so the definite form sounds natural.

This kind of definite form is very common in explanations and technical descriptions, where English might or might not use the depending on style.

In Norwegian, it is very common to leave out the indefinite article in general, descriptive, or technical-style expressions, especially after a preposition like med.

So:

• med lang lukkertid = with long shutter time / with a long shutter speed
• med en lang lukkertid is also possible, but it sounds more like you are thinking of one particular long shutter time

Without en, the phrase sounds more general:

• in conditions of long shutter time
• when using a long shutter time

This kind of article omission is very common in Norwegian style.

Because lukkertid is a singular common-gender noun, and the adjective before an indefinite singular common-gender noun normally stays in its basic form.

So:

• lang lukkertid = correct
• langt would be used with a neuter noun
• lange would be used with plural or definite nouns

Compare:

• en lang dag
• et langt opphold
• lange dager
• den lange dagen

So here:

• lukkertid is singular
• it is not definite
• therefore the adjective is lang

Lukkertid is a photography term. It is a compound noun:

• lukker = shutter
• tid = time

So it literally means shutter time.

English often says shutter speed, but Norwegian very often uses lukkertid, focusing on the duration the shutter stays open rather than calling it a speed.

So even if the English equivalent shown to the learner is shutter speed, the Norwegian word itself is closer to shutter time.

Øker is the present tense of å øke.

• å øke = to increase
• øker = increases / is increasing

A useful thing for English speakers: Norwegian verbs do not change form depending on the subject.

So you get:

• jeg øker
• du øker
• den øker
• de øker

The form stays the same.

In this sentence, øker is used intransitively, meaning the subject itself increases:

• Bevegelsesuskarpheten øker = the motion blur increases

Yes, med literally means with, but here it is being used in a broader sense.

In this sentence, med lang lukkertid means something like:

• with a long shutter time
• at long shutter times
• when the shutter time is long

So med is introducing the condition or factor associated with the increase.

This is very common in Norwegian. Prepositions often do not match English word-for-word, so it is better to understand the whole phrase than to translate med too mechanically.

The sentence follows normal Norwegian main clause word order:

• Bevegelsesuskarpheten = subject
• øker = verb
• med lang lukkertid = prepositional phrase

So the pattern is basically:

subject + verb + other information

A key rule in Norwegian is that the finite verb usually comes in second position in a main clause. This is often called the V2 rule.

That means you can also move the prepositional phrase to the front:

• Med lang lukkertid øker bevegelsesuskarpheten.

That is also correct, because øker still stays in second position.

It is understandable, but it changes the feel of the sentence.

• Bevegelsesuskarpheten øker ... sounds more like you are talking about the motion blur as the effect under discussion
• Bevegelsesuskarphet øker ... sounds more abstract or dictionary-like, and is less natural in this kind of explanatory sentence

In technical or instructional Norwegian, the definite form is often preferred when referring to a phenomenon that is being discussed as a recognizable effect.

So the version with -en is the more natural choice here.