Die Bildauflösung ist für die Bilddatei wichtig.

Because Die Bildauflösung is the subject of the sentence — the thing being talked about.

• die Bildauflösung = the image resolution
• ist = is
• für die Bilddatei = for the image file
• wichtig = important

So the basic structure is:

[Subject] + [verb] + [other information]

German main clauses usually put the finite verb in the second position, which is why ist comes right after the subject.

In a normal German main clause, the conjugated verb usually comes in position 2.

Here:

• Die Bildauflösung = position 1
• ist = position 2
• für die Bilddatei wichtig = the rest of the sentence

This is a very important German word-order rule.

You could also move another element to the front, and then the verb would still stay in second position:

Für die Bilddatei ist die Bildauflösung wichtig.

That still means basically the same thing, but now für die Bilddatei is emphasized more.

Both nouns are feminine singular, so they use die here.

But the two die are not doing exactly the same job:

• die Bildauflösung is nominative because it is the subject
• die Bilddatei is accusative because it comes after für

For feminine singular nouns, the article is:

• nominative: die
• accusative: die

So the form stays the same, even though the case is different.

Because für is a preposition that always takes the accusative case.

So after für, you need an accusative noun phrase:

• für den ... masculine
• für die ... feminine
• für das ... neuter
• für die ... plural

Since Bilddatei is feminine, it becomes:

für die Bilddatei

This is worth memorizing: für + accusative.

Because wichtig is being used as a predicate adjective, not an adjective directly before a noun.

Compare:

• die wichtige Bilddatei = the important image file
  
  • here, wichtige comes before a noun, so it gets an ending
• Die Bildauflösung ist wichtig. = The image resolution is important
  
  • here, wichtig comes after sein, so it does not get an ending

After verbs like sein (to be), werden (to become), and bleiben (to remain), adjectives usually stay in their basic form.

Yes, Bildauflösung is one word because German very often forms compound nouns.

Here:

• Bild = image / picture
• Auflösung = resolution

Together:

• Bildauflösung = image resolution

German combines nouns into one longer noun much more often than English does. English often writes these as separate words, but German usually writes them as a single word.

The same is true for:

• Bilddatei = image file
  
  • Bild
    • Datei

In many German compound nouns, the last part decides the gender.

• die Auflösung is feminine, so die Bildauflösung is feminine
• die Datei is feminine, so die Bilddatei is feminine

This is a very useful rule for compound nouns:

The final noun is the main noun, and its gender determines the gender of the whole compound.

Because in German, all nouns are capitalized.

So you get:

• Bildauflösung
• Bilddatei

This is normal German spelling, not special emphasis.

Adjectives and verbs are usually not capitalized unless they begin the sentence, so:

• wichtig is lowercase
• ist is lowercase

Yes. German word order is flexible, as long as the verb stays in second position in a main clause.

For example:

Die Bildauflösung ist für die Bilddatei wichtig.
This is the most neutral version.

Für die Bilddatei ist die Bildauflösung wichtig.
This puts more emphasis on for the image file.

Both are correct. German often changes the first element to shift emphasis or topic.

Yes. In this sentence, für means something like for or with regard to.

So für die Bilddatei wichtig means:

• important for the image file
• important in relation to the image file

It shows what something matters for.

This is a very common use of für in German.

The main stress would usually fall on the most important information, often Bildauflösung and wichtig, and sometimes also Bilddatei depending on context.

A natural reading might sound like:

Die Bildauflösung ist für die Bilddatei wichtig.

If you want to emphasize that it matters specifically for the file, you might stress Bilddatei more.

In general, German compounds like Bildauflösung and Bilddatei usually get their main stress on the first part:

• BILDauflösung
• BILDdatei