Participle Clauses

A participle is a form of a verb - either ING or Past Participle (3rd form of a verb). A participle clause is a subordinate clause which begins with a participle. They act like adverbs and are linked to the main clause of a sentence. They usually show things like event order, time, cause and effect:

Stepping on camera, I relaxed completely. (When I stepped on camera)
Filmed inside, the footage was too dark to use. (Because it was filmed inside)
Fried in lemon, the fish would taste delicious. (if the fish were fried in lemon)
Turning round slowly, I tried hard not to make a sound. (As I was turning round slowly)

It is very important to remember that participle verbs do not change their form to show tense. This actually happens in the main clause, and participle clauses usually mimic the same tense as the main clause:

Stepping on camera, I relaxed completely. (When I stepped)
Stepping on camera, I relax completely. (When I step)
Stepping on camera, I will relax completely. (When I step - future time clause)

However, it is possible to put a tense in a participle clause by itself. For example:
Knowing I was filming today, I wore a shirt.

Participle clauses often have implied subjects. This means that the subject of the participle clause is the same as the subject of the main clause and so it is omitted in the participle clause. For example:
Seeing the mistake, she corrected it immediately. (When/ because she saw)
Feeling unwell, he went to the doctor. (Because he felt unwell)

However, it is possible for a participle clause to have its own subject – and this is a little bit more formal. So, for example:
Seeing she had made the mistake, she corrected it immediately.

Be careful not to make a pariticiple clause with a confusing subject:
Seeing it fall, the tree hit me in the back. (This implies the tree saw it fall - Better to say 'As I saw it fall' or 'When I saw it fall')
Feeling weak, the boy attacked the man. (Who is feeling weak here? - Better to say 'While the man was feeling weak, the boy attacked him') 

To make a participle clause negative, we use ‘not’, and this comes before the participle verb.  So, for example:
Not knowing the baby slept, she phoned.
Not seeing the bus, the dog stepped into the road.
Not saying anything, she poured the glass of water over his head.

However, the ‘not’ can come after the participle verb depending on your meaning. So, for example:
Not knowing the baby slept, she phoned. (Because she didn't know the baby slept.)
Knowing not to call because the baby slept, she waited until the next day. (Because she knew not to call...)

To make clear that one action is finished before the action in the main clause is begun, we use Having + the past participle. And this basically works the same way as ‘because’ or ‘after’. So, compare:
Putting away the equipment, they talked about going home. (While putting away...)
Having put away the equipment, they went home. (After they had put away...)

Other examples:
Having been to France, I can speak French. (Because I have been)
Having unpacked the suitcases, she took a shower. (After unpacking.)
Having decided what to do, I made my move. (Because I had decided)

Finally, all sorts of prepositions can sit before the participle verb to further emphasise or clarify events’ order, time, cause and effect. Words like after, before, since, while and with. So for example:

After eating, we sat on the couch.
Before leaving for work, they watched TV.
While waiting, I thought about my family.
Since coming to England, I have met a lot of new people.
By practising every day, she passed her driving test. (Because she practised - this describes the method)
Without knowing it, I had ruined everything. (Although I didn't know it)