Cinematography: Exposure Experiments

In our second Cinematography class we joined the Photography class to learn more about the exposure triangle, and define a few terms.

The Exposure Triangle. (2013). Retrieved from http://djshawphotography.com/new-dslr-the-exposure-triangle/

The Exposure triangle is made up of the Iso, Aperture and shutter speed; which are the key elements that need to be correctly balanced to achieve correct exposure in a photo or film.

Aperture: Measured in F-Stops, this refers to the lens or eye of the camera which can be opened of closed in order to let in light.  The F-Stop is a ratio between the diameter and the length of the lens.  An F-Stop of 22 is has a smaller diameter opening and lets in less light than an F-Stop of 1.4, and each stop either doubles or halves the amount of light let into the camera.

Shutter Speed:  The shutter speed is measured in time, and refers to how long the shutter is open.  Shutter Speeds are given in fractions of a second.

ISO: ISO is the sensitivity of the camera's sensor.  If a camera is being being used in low light then the ISO may need to be increased.

Each of these elements are affected by light, which is the main factor influencing any changes to these settings.  In order to correctly exposure a photo these elements need to be balanced.  The most commonly noted connection is the relationship between Aperture and Shutter Speed.  If a low F-stop (eg 1.4) is used, more light will be entering the lens. To counterbalance this a faster shutter speed must be used to limit the amount of light and prevent overexposure. 

Low F-Stop (1.4) = Short Shutter Speed
High F-Stop (22) = Long Shutter Speed

These are all things I learnt during photography classes taken at school, so they are all familiar concepts.  However in regards to film, this is something that will take a little bit to wrap my head around, as it is obvious to me how these things affect a stills camera but not so clear how this translates.

To illustrate these ideas further we completed an exercise where we needed to take a number of correctly exposed shots using as many different Apertures as we could.  For this exercise the Shutter Speed and ISO were locked, although we did alter the shutter speed once during the exercise to allow for the weather conditions.  This ended up being a really useful way to show the theory in practice.

Cinematography: Shutter Speed Experiments

Over the past week I have had my first two lessons in cinematography, with the main subject of these classes being the relationships between exposure, shutter speed and f-stop.

The first exercise we completed in class was to look at the connection between shutter angle or frame rate and exposure.  Our camera was set up to film at 50i which gives interlaces footage.

We filmed a series of clips at different frame rates to experiment with this, and what we found was that filming with a higher frame-rate caused there to be less motion blur and strobing then the footage that was shot using lower frame-rates.  The higher the frame rate the more crisp the image became, and it began to look almost too clean.  The footage also demonstrated the relationship between the frame-rate, aperture and the resulting exposure of the footage.  As we increased the frame-rate the footage became more underexposed.  Something worth mentioning is that filming at higher frame-rates gives an opportunity in post-production to slow down footage without losing quality.   

Wanting to understand more about this I found an article that discussed the affect of shutter speed on video.   There was some interesting information there that talks about high speed shooting etc, but I also found a youtube clip there that demonstrates essentially what we were trying to explore in class (aside from the link to exposure). 



In animation we always rendered for HD delivery, using 25fps Progressive, so I wasn't sure what effect filming at 50i would have on our footage.  Obviously the main difference between interlaced and progressive is to do with the field order, or how the image is delivered on screen, but how filming in either format affects the footage was beyond me.

Since I really didn't know much about this format I decided I had better do some research about the difference between interlaces and progressive.  I started out by reading a number of articles which talked about this topic.

Essentially interlaced footage is delivered in two passes, or fields.  Each field contains half of the horizontal lines which make up the image, with one field containing the odd numbered lines and the other the even numbered.  Each field is displayed alternately, for 1/50th- 1/60th or a second (depending on the frame rate) which gives an illusion of a complete image

Most of the articles I read agree that Interlaced footage shot will deliver a crisper image of fast movement, but some say that very fast movement will cause softening of the image. Interlaced footage can also cause a strobing effect or artifacting when filming things such as striped shirts, plaid jackets or bricks.  Interlaced footage is sometimes considered to give a more news broadcast look to film, and I read that is can also give good results to sports etc.  

Progressive video displays the entire image at the same time, with each frame containing all of the image information.  Because all of the information is shown at once, the images appear smoother and sharper with less artifacting. It takes more bandwidth than interlaced footage but this is steadily being improved due to digital storage and transmission.  (ISF Forum, 2007).

Articles:

"Choosing your direction: Progressive or Interlaced". (2008). http://www.videomaker.com/article/13755-choosing-your-direction-progressive-or-interlaced

"What's the difference between interlaced and progressive video?". (2007). http://www.isfforum.com/FAQs/view/All-About-HDTV/What-s-the-Difference-between-Interlaced-and-Progressive-Video/33.html

"How does shutter speed affect video?". (2013). http://photography.tutsplus.com/articles/quick-tip-how-does-shutter-speed-affect-video--photo-12092

A New Year and New Challenges: Interning on Human Traces

It seems unbelievable that it is nearly the end of February already.  Classes are started up and projects are kicking off.  I haven't actually had the chance to go to many of these classes yet though, because I've had something pretty exciting to work on.  Since last Wednesday (11th) I've been Interning on a test shoot and trailer for Human Traces, a feature film that will hopefully be shot later in the year.

Human Traces is being produced by Nadia Maxwell of Overactive Imagination.  Nadia has worked as a Producer and Production Manager for many years on short films, documentaries and television commercials which have been broadcast on TVNZ, TV3, National Geographic, FilmFour (Channel 4 UK) and Al Jazeera International channels.  Human Traces is written and directed by Nic Gorman, who has been long involved in the creative industries: theatre, fiction writing and film.  Nic and Nadia worked together on a short film Here Be Monsters which won Best Short Film, 2013 Rialto Channel New Zealand Film Awards; along with many of the same crew involved with Human Traces.

For this internship, along with Lee, I took on a role as a production assistant/ runner.  This was my first internship, and because of my animation background, only my 4th film set that I had been on.  This also meant that a lot of the film talk went over my head, and my inexperience showed itself many times.  As it worked out Lee did most of the heavy-lifting production-wise, while I did more running and helped out Ruby with Art Department.  On the days leading up to shooting I found myself doing a few data entry type tasks, as well as arranging for rental cars and hotels.      

I feel that this worked out well for Nadia who was the producer on this test shoot as it played to the strengths and knowledge that both Lee and I had already.  Lee knows a lot more about producing than I do, so was able to take more of the pressure of Nadia.  Whereas because I have less knowledge I was better suited to clearly defined tasks.

While on set I was mostly responsible for making sure people were comfortable, that they had stopped to have a drink and snack or had sunblock on if we were outdoors.  The sole difficultly I had with this, was picking a moment where I wouldn't be interrupting the flow of things.  It was really difficult to tell from my station outside what stage the actors and crew were at inside the building, and whether it was a good time to enter.  I was really aware that by choosing the wrong moment I could throw the crew and actors off there game, or even ruin a shoot.

I learnt a lot on this internship, both from observation of how things were done on set, and also a few personal achievements.  One thing that I had been really nervous about leading up to the internship was the prospect of having to drive unfamiliar vehicles in an unfamiliar area.  This nervousness about driving is something that I experience often, as I have barely driven for the last 3 years and feel out of practice.  I also have a notoriously bad sense of direction, and had never driven a van before.  Needless to say, I spent a fair bit of time during the days before filming pouring over maps of the area.  We had a few issues with trips to get things (including lunch) taking longer than anticipated due to road conditions.  I think if I were to be a runner again I would try to be more aware of this and try to leave additional buffer time. 

I was really lucky that my first internship was with such a nice group of people, who were really understanding towards my mistakes.  I think that for future internships in this same position, knowing more about production would make things a lot smoother, and allow me to be more useful to the internship providers.      

I came across this article that mentions the test shoot, and also about Lee and I interning on it.
http://www.stuff.co.nz/southland-times/66159350/Southland-a-playground-for-filmmakers

Internship Hours: 80hours.