Category: Lessons

Getting to know you.

8) What’s It Mean? Contrast…Part 2

In Part 1 of the Contrast Lesson, a simple definition was introduced, with a few examples. Then you were requested to notice details in bright light and shadows while you live life.

Why?

Because there is a difference between what we perceive and what we are aware of. Your job as a professional-in-training is, 1) to learn how to be aware of things that you already perceive, then 2) how to communicate well when things are not as good as they should be.


We don’t think about it, but most of our vision is out of focus and not colored. Take a moment to observe: While you focus on this page, much of everything else is very out of focus, and most everything is greyish. You can still see movement if it happens – even in the out of focus areas. You can even tell the direction of a movement. [Sound is similar; while concentrating on something, non-important sounds get ignored, just part of the background, but an urgent noise will be noticed quickly, and with very precise location.]

We are constantly perceiving, even if we are not paying attention to something.

When our eyes blink, we rarely notice – but part of our vision went black for a while! How can we not notice that? When we see someone sitting at the table, we rarely notice the variations of color on their pants or their socks or their shoes. We glance and see the shoes as red. But if we look closely we actually see that the color might be dozens of shades of bright and dark red. If they are in shadows, that red is mostly dark, and some parts might actually be black.

The same shading is happening on the movie screen when you look at it…or at least it should be. If it isn’t, there probably is a problem. Your customers may not know what is wrong, but they will have a feeling that something is wrong. If it is irritating they may just not come back, even if they can’t describe it.

Sometimes you go in to check the picture only to get sucked into the movie and forget to stare at the dark or bright parts of the scene. These are the parts that will inform you if the equipment is working well. There should be detail in the bright – soft shades of colors – and most importantly, there should be exquisite detail in the dark.

So, trick number one. Don’t forget what you are looking for. Trick number 2…Look. Trick number 3: Become better at being aware of what you see…difficult at first but wonderful when you get used to it.


There is a technical way to measure light. If you promise not to laugh, we’ll tell you that it is based upon the light of one candle. All that stuff in Lesson 1 was true.

The term is candela and the measurement for the reflected light from the screen answers the question of “How many candles of light does it take to make the eyes perceive bright white.

The answer is: 48. 48 what? 48 candela per square meter.

Oh my. What is a square meter?


A meter is one of those obscure things for Americans, but very common every place else in the world. And, a square meter is even more odd. Let’s walk through this.

Put your arms out in front of you with your hands flat, facing down. Now, keeping your hands flat and at shoulder level, bring them toward the front of your neck and place the ends of your middle fingers together. Your arms make almost a straight line now. From elbow to elbow is about a meter. Some people will have a shorter distance, some a longer. Doesn’t matter for this purpose. Imagine that length at the bottom of the movie screen. Imagine the sides of a square going up the screen, but only for the same distance. The box with all those equal sides is about a square meter.

Imagine that only that square meter of screen will reflect light…the rest of the screen is dark and actually eats light.


Now, imagine a candle in a dark room shining on your square meter of screen. Put your imaginary candle one meter away from the screen. The light reflects back to you. That is one candela of light per square meter. And that, friends, is also Luminance. And luminance is what technicians measure off the screen with their fancy equipment.

And, if you want to be really cool, if you want to use the word that directors and cinematographers and colorists use, say ‘nits’. “Yeah; the screen is 48 nits…I saw them shoot it with the meter.”


Back to Contrast

Who cares? The picture is on the screen, the sound is hot, the popcorn didn’t burn this morning…all is good.

And maybe it is.

In a perfect world the contrast is the range or difference between what looks like white and what looks like black on the screen.

In most auditoriums, there is no real white on the screen or real black on the screen. There are many reasons for this, and it will always be this way. Even the most fancy DolbyVision, or Laser IMAX or Sony or Samsung LED wall doesn’t have as much light as a foggy day. But that is a lesson for another time.


There is a range that each room is capable of, and the equipment is in a war to try to make it stable …which it always loses. A bulb gets weaker, electronics get too hot or finds some other reason to fail. The screen material gets darker every week and month and year as it ages – and yellowish instead of whiteish –  and sometimes computers just don’t talk to other equipment correctly.

Since it is your job to ensure quality, it is your job to decide whether contrast has reached a point of concern. So, it is time to learn how to judge it. Here are some examples.

When you see someone’s leg under a table or something in a shadow during a movie, you have an opportunity to “See Into The Dark”. At worst, you won’t even see that a black shoe isn’t part of the shadow. At best, you will see that there are different shades of black and grey in the shoe and sock and the pant cuff and the folds in the pants. Notice these things in real life, notice how there is a constant gradient in dark shadows, and how a colored floor will go off to black in the distance.

The opposite will happen in the brilliant whites and colors. There will be ‘blown out’ white where things are not distinguishable at all…just one flat and too-bright-to-look-at white. The funny thing is, the brightest that the very best projector and screen combination can create is 108 units of light, and most strain themselves to create half that.

[Remember from the lesson above: The standard is 48 candela per square meter, which again, simply means: the amount of light that would be created if you held 48 candles at a distance of one meter (3 feet) in front of the screen, then measured all the light reflecting from one square meter of the screen (which is about nine, almost 10 square feet).]

Outside, 100 units are nearly nothing. The reflection of the sun on a car is thousands and thousands of units. (Perhaps we should stop saying ‘units’ since we know that people in the industry call that unit of light a ‘nit’. Just don’t get confused when a tech uses an older term like Foot-Lamberts. 48 nits…48 candela per square meter is equal to 14 foot-lamberts. And yes, it was named after Mr. and Mrs. Lambert’s son. He was famous for a lot of things.)

On-screen, look at some bright part of the sky or something flat and nearly one color – a refrigerator, for example, or even a close up a white dog. The white should actually be many shades of white. You’ll see that this is true of a real dog, or a real sky, and the same is on screen: One solid, flat color is wrong (except in a cartoon!) A smooth gradient of white to lighter or darker white, or another color is correct. There will be shadows in the hairs of the close up of that white dog as well.

So, that is your task. Learn about Contrast by looking: What looks natural in real life and on screen. At first you will write to the tech and say, “In auditorium 5, it really seems like something is wrong in the shadows, but I don’t know what…it is better in the other rooms.” As your abilities grow you’ll be able to say, “The gradient in the darks is off in auditorium 5, they get muddy too quickly. The blues especially seem wrong…it seems like the yellows go toward the brown instead of toward the greens.” Won’t that be fun?

Do well and enjoy the ride.

 

10b) What Does It Mean: Scope and Flat? Part 2

Scope or Flat can best be shown with some examples of how it goes wrong. These drawings were made because exactly this problem happened in a local screening room for a movie screening to a room full of experts.

The intention isn’t to make fun of anyone, of course. These things happen by mistake more often than by negligence or bad repair. The screening company representative said that there was a run-through previous to the showing and everything was fine. Since she left the room after her welcome statement, we don’t know if what we saw is what she saw previously. It is possible that she didn’t know what to look or listen for, which is exactly why we need to document this. This Lesson will help you to understand this situation, recognize it right away as you do  your auditorium inspections…and fix it right away. Continue reading “10b) What Does It Mean: Scope and Flat? Part 2”

1) What Does It Mean: DCP

Let’s start with something that we will hear about all the time.

A DCP is a Digital Cinema Package. You will never hear, “Did we get the Digital Cinema Package?”. No one will ever say, “Will you play my independent movie please? I can send you the Digital Cinema Package.” No. Instead, they will say, “We got the DCPs.” Or, “I’ll send you the DCP on a hard disk.”

Yes, it is digital, and it is cinema. Digital simply means that is capable of being used by a computer. In case you are not certain, the projector, and the media player for the projector, and sound system are basically just specialized computers. Cinema, of course, means that it has something to do with motion pictures, usually in an auditorium. (The word “cinema” hasn’t had a long life, only about 100 years. The originators of modern motion pictures, the Lumiere brothers, chose the word from the Greek word from Ancient Greek word kínēma – which means “movement”.)

The reason the DCP is called a package is that it holds all the frames of the movie, plus all the music, dialog, sound effects, all the subtitles and the files for the blind/partially sighted, deaf and hard of hearing, and the security keys. In addition, the package has some extra files that tell the computers which of those files to play, and when. Continue reading “1) What Does It Mean: DCP”

10) What Does It Mean: Scope and Flat?

The first question: Why Do We Care?

Every Answer begins the same way: There are many things that can go wrong with the presentation of the moving picture.

In this case, we are working with the shape of the picture. Movies evolved from almost square to very wide.

This topic is a little tricky. Even if the shape is wrong – too narrow or too short – at least the image is on the screen. In some cases, the images may look OK if you just glance at the image. But there are things to look for.

Will the audience care? Many will. They will think that the screen looks too small, or the image looks too small. (Nobody ever complains about too big!) They may complain that the people on screen are too thin, or too fat.

Buzzwords: “Scope” “Flat” “Format” “Constant Height” “Constant Width” “Aspect Ratio” “Two-Three-Five” “One-Eight-Five” (written 2.39 or 1.85 and 2.39:1 or 1.85:1). We will show the definition of these terms with examples. Don’t look them up now – they have too many meanings and most explanations are more complicated than we need to be.

The Complication: There are 2 correct forms for an image on the screen. Even in the same facility, some auditoriums may be one type, and other auditoriums may be the other type!

Masking and Curtains in a Cinema Auditorium

Potential Points of Failure: Screen. Curtains. Motors for Curtains. Cord for Curtains. Masking. Motors for masking. Chains for masking. Automation Electronics. Projector. Automation setting on Playlist. Instructions that tell which setting to put into the playlist!


Don’t let this get too complicated. We are only talking about the size of the rectangle of the movie on the screen.

Movies are created in 2 different shapes. The measurements for both of them is just about 2 times as large side to side (the width) compared to the dimension from top to bottom (the height). For example, the following picture shows this concept of a rectangle that is 2 times wide and 1 times high.

A pretend cinema screen two times wide and one times high

A simple way to write this is ‘2 to 1’ or ‘2:1’, which means 2 units in one direction compared to 1 unit in another direction.)

The important things to remember is:

There are two formats

One format is slightly smaller than 2 times wide and 1 times tall – that format is called Flat.

One format is slightly wider than 2 times wide and 1 times tall – that format is called Scope.

Here is a picture of those 2 formats placed with our 2 to 1 picture.

Two to One, with Flat and Scope

The choice for this happens very early in the movie making process – probably during the first hours of conversation between the producer and director, or sometimes the director and the cinematographer. Will we shoot this movie wide or do we shoot this movie tall?

Of course, they don’t use those terms. Art and Science are never that simple – there are always special words, or words with special meanings. They choose between “Scope” or “Flat”.

There is no rule that says a movie should be one way or the other. Sometimes a director will only work in one form, then suprise you by making a movie in another. Or, sometimes people will say that all action movies are in Scope. But a little research will show that isn’t always true.

Anyway, after the director’s decision, every scene of that movie will be shot through a lens that is in that form – what is called a format. And of course, the last lens of the movie process – the lens that is attached to your projector – will make the movie appear in that format on your screen.

Here be dragons!Maybe you remember those old maps with the ship at the edge near the sign that says: Warning – Here Be Dragons~! Well…Warning — Here Be Maths~! …and, yes, we promised to keep math to a minimum. But there will be drawings too, with arrows and bright colors. So, be brave. Continue reading “10) What Does It Mean: Scope and Flat?”

7) Measuring Light

For this Quality Assurance Project, there are many goals (I want to learn a bit more about the technology of movies, or, I want to be part of a well trained team that keeps customers happy…) and many purposes (If I can help create happy customers, they come back more often…or, if I have good control of the basic skills, I can use them to get even more important skills.) To accomplish these goals and achieve these purposes, there are many things that need to be done.

The top layer of these goals and purposes is responding to the quality of presentation that the CEO (Cheif Executive Officer of the company) intends them to be. She or he will acknowledge that there is a range of possibilities: Perfect Perfect, Perfect, Kinda Perfect, Mostly Kinda Perfect, OK, Kinda OK…all the way to I’m embarrassed but maybe someone won’t notice and the boss won’t hear about it.

(in the auditoriums  ensuring that the are  – acknowledging that not every room is a Palace of Perfection. Another layer has to do with ensuring that each patron is satisfied with what the facility and staff have to offer, which also includes an educated staff that is able to communicate intelligently with patron and tech staff.  Fortunately, they don’t all have to be done at the same time. They can be added too and tweaked and made better and more as time goes on.

So, if at first you don’t have the organizational support to download DCPs onto a USB drive, then get the DCPs into the Media Player/Projector system right now – you can still download some audio and light measuring tools, and experiment with them until you can use them easily in a dark room.   Continue reading “7) Measuring Light”

6) Measuring – Sound

Since there are many goals and purposes for this project, there are many things that need to be done. Training is high on the list. Practice should be high on the list…but who has the time!?!?
Perhaps you don’t have the a friendly tech or projectionist to

  • download DCPs onto a USB drive and
  • load them into the Media Player/Projector system and
  • make a nice playlist,

You can still download some audio and light measuring tools, and experiment and practice with them until you can use them easily in a dark room.  Continue reading “6) Measuring – Sound”

4b – Audio (Sound Basics): Part 2

Before we took a break from Part 1 of Audio (Sound Basics), we had some tasks.

Become more aware of sounds in the background,
Become aware of differences in the many kinds of sounds around us. And finally,
figure out what sounds are annoying to you.

Every good speaker designer has to learn these things too. Every good designer of auditoriums need to learn these things. Why? Because sound all by itself is complicated, but to make sound go through speakers and reflect of ceilings and walls (and people!), they can take classes and study angles and which magnets are the best to use in different speakers – all that science stuff. And, they also need to know the things that artists know. How to observe. What is pleasant, what is disturbing. Because: Acoustics, designing rooms for sound, is a science, but very importantly, it is an art.

They can design a perfect room. They can set it up with the best equipment to have perfect balance. But when they play their favorite movie scene or recording, they often listen find things that are annoying.

You do not need to know about the 10 or 20 parts for each speaker, or the details about each speaker in each speaker box, or the special wire that connects the speakers to the amplifiers in the best system. You don’t need to know details about the media player and the audio processor and the every part of those.

Putting together all the parts is an art and a science for others.

You should be aware that these things exist. You should be aware that these things can have problems. But mostly, you need to be aware of…to learn how to… listen.


We will work on

1) listening to sound. And we will also learn how to,

2) listen to audience members, and

3) how to listen well enough to fill in the audio questions of the Managers Walk Through Form.


And now, our first real technical word: Frequency.

Frequency is a term that is used when describing both sound and picture. So we will need to get a good idea of it. Let’s do a quick once over to remove a little mystery out from the subject.

Think of a song. Think of the beat. . . . . . . . . . Count that beat for 15 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .For this exercise we are going to use the number 30…30 beats every 15 seconds. That is 2 beats every second. If we counted for 30 seconds we would have 60 beats for every 30 seconds. And, for 60 seconds, 120 beats. 120 beats per minute. 2 beats per second. You can clap your hands that fast. Imagine the beat being 4 times faster…8 times every second…that may be faster than you can clap your hands.

Beats every second is a frequency. Beats every minute is a frequency too. Beats every day is a frequency, but the number may be too huge to count…and your hands would be pretty tired! But, the planet has made 1 revolution around its axis in one day…1 revolution every day is a frequency. And the planet earth will go around the sun in 365 days…1 every 365 is a frequency.

People usually say the word “per” instead of “every” when we talk about frequency. 1 revolution per 365 days. And sometimes we have to be careful – does that mean 1 revolution around the axis or 1 revolution around the sun? But with music…that is, with sound…and color…that is, with light…people understand that we are using seconds.

And, instead of beats we use the word “cycles”. Cycles are a little more fun.

When you clap, your hands go toward each other, then away from each other. They wave at each other going one distance out and then back in.

Waves are like that. They repeat their sequence. You can start counting the wave when the hands hit…the bottom of the cycle, or you can start counting the wave when your hands are farthest apart. Or start someplace in the middle. The important part is the cycle of the wave and the time. Cycles per Second. Cycles per Year. Cycles per Decade.

Cycles. Time. Frequencies.

Sound frequencies are very easy to think of when we consider a musical instrument like the piano. From left to right, the notes start with the low and rumbling sounds and and go all the way up to the twinkling high notes. If you look at the longest strings of the piano as they are hit, you can almost see the back and forth slow motion vibration as they move through the air – and they act on the air – creating those low notes that hit our ears. If we look at the strings a few notes higher, they move so fast that we cannot see them vibrating.

The same is true for the guitar, which is easier to make a video of. Here is a video showing the strings moving in slow motion. Longer and shorter waves for each string…Cool! Longest waves for the bass, the low notes, the low frequencies. Shorter waves for the higher frequencies…but notice, there are more waves on the 3rd string than on the 1st string. Almost 4 waves on the 3rd in the same distance as 2 waves on the 1st. 4 waves per …something, compared to 2 waves per …something. Higher frequency, shorter wave length.

Hmmm…there is something here to study later…some reverse relationship between wave length and frequency. Let’s put that aside for later. It is just interesting, but not important right now.

So, a quick review. Frequency is the number of times that something happens, associated with a unit of time.

I saw my friend quite frequently…about once a week (for example.)

Once per second I am able to type a word…the frequency of my typing is one word per second.

The strings on the lowest note on the piano – the one on the far left – goes back and forth 27 and a half times every second. We say that it has a frequency of 27.5 cycles per second. Some of the notes in the middle of the piano go back and forth over 400 times per second – the ‘A’ note above middle ‘C’ is 440 cycles per second. The very highest strings vibrate at over 4,000 cycles per second.

Now. Why do we need to know about frequency?

Because customers will come to you and say, “The low frequency notes are buzzing.” And you can say, “Ah. Help me to understand more. Do you mean the low frequency, like the rumble of the explosions, or the low frequencies like the man’s voice?”

And your customer will think, “This person is interested and capable of getting this problem fixed – I’ll come back here!~”

Then you can tell the tech – “Yeah, like, the low frequency hits are causing some buzzing in auditorium 7. A customer told me, then I listened and it seemed like the LFE has a cracked speaker. It only breaks up on certain notes.”

The tech can now come into the auditorium with the right equipment, then find and repair the problem in a few minutes.

What was the alternative?

The customer says, “Hey. I’m watching Galaxy 9. Low Frequencies are busting up in auditorium 7.” Your new and uneducated employee falls asleep when the word “frequency” is used and forgets the customer even said an auditorium number. The tech gets a note that says, “Customer says sounds is messed up in one of the auditoriums that Galaxy 9 is playing in.” Tech comes in, has to play a bunch of stuff before hearing which sounds and what speakers are messed up. Spends more time going to get the speaker. Schedules a whole morning 3 days from now to get it fixed. Customers are unhappy.

Part 3 of Sound Basics will follow. But take a few days before you attack that. Listen to sounds again. Judge the difference between low and mid and high frequencies. Listen how most male voices are low, but not as low as many other low sounds. Be aware of your sensation of touch – how often you can feel low frequency tones on the arm of the chair for example.

Take a look at the Managers Walk Through Form. Notice the other sound questions. Get comfortable with the idea of listening for those things, at different places in the environment.

Sound Section of Managers Walk Through Form
Sound Section of Managers Walk Through Form

If you are really brave, dive into the Lesson: So Now You Want To Measure Sound. Go ahead. It is a good idea to get some physical experience instead of all these theory lessons every time. (Theory lessons per week…frequency.)

And, remember these two things: No one was born with this info. Everyone had to learn it, to experience it, to mess up, to learn again, to get better then mess something else up…don’t get discouraged.

And two, keep it fun. On this path are rocks and sand and dust and great distances between knowledge. Scientists still discover things about sound and hearing, just like they do with light and pictures and vision.

Don’t forget to write questions or thoughts in the Comments or in the Contact Form. Let us know what we could explain better, or didn’t explain at all.

Thanks…and until next time (Part 3 of Audio, Sound Basics ), keep a steady beat.

6) So Now You Want To Measure Sound Level

Hopefully you have read through the post named Basics: Audio (Sound), Part 1 and Part 2. It is good to have a basic understanding of frequencies and speakers and surround and amplifiers and level and Loudness. Hopefully you’ve noticed some of the many ways that the human hearing system has made things “interesting” in normal life, and while you have walked around your cinema theaters since learning more about these things. Continue reading “6) So Now You Want To Measure Sound Level”

9) What’s It Mean? Distortion??

Let’s do this again. We will go through a term that everybody uses but which has a different meaning depending on who you talk to. Which meaning do we care about? The meaning that will correctly get an idea across to the Tech Team. We must describe a problem so it can solved quickly and well.

Distortion – For our purpose, distortion is the term that describes the imperfect recreation of the original sound of the motion picture. There are other definitions and uses, including the use with picture details such as ‘brightness and contrast problems’ or ‘focus problems’ or different kinds of color and screen problems. Continue reading “9) What’s It Mean? Distortion??”

8) What’s It Mean? Contrast…

As usual, the first question for every “What Does It Mean” topic is: Why Do We Care?

Every Answer begins the same: there are many things that can go wrong with the presentation of the moving picture. In this case, we are working with how much dark and how much bright there is on the screen.

This one is a very tricky. The image is onscreen. In most cases, the images may look OK if you just glance at the image, or if you don’t know what to look for.

Will the audience care? Maybe not. They don’t know what “Correct” is.  They will think that the picture lacks “Pop”, or some other quality. But if you don’t know that the black suit is really supposed to have fine light blue lines in it, then the black suit might look OK.

Buzzwords: “Black Levels”, “Crushed Black Level”, “No Greys”, “Gamma Problem”, “Brightness”.

We will show the definition of these terms with examples of how they apply to our situation as someone who is checking the quality of the picture. Don’t look them up now since they have many meanings and most are more complicated than we need.

Complication: Almost all cinema projectors have a problem creating perfect blacks. But there is a range of deep blacks and deep grays that they should create without problem.

And white too! Perfect white is never shown – it would ruin your eye’s ability to notice differences between things when the picture is too bright.

Which is the problem with Contrast…too bright, you can’t see details in the darks. Too dark – muddy – you can’t see the detail in the bright.

There needs to be a good range – when you look in the dark, in the shadows, there should be richness in the dark reds and and dark blues and and dark greens and and greys. And when there is is bright scene, there should be good pastel colors too.

Another problem is – We don’t always know what the artist wanted – a lot of movies are ‘moody’ and ‘dark’. But even dark movies shouldn’t be mushy.

Potential Points of Failure: Bad setup on the Projector. Wrong Lens. Port Window, if very dirty. Old screen. Dirty screen.


Look at these three versions of the same winter scene at Yosemite Falls in California.

In the first one, you can see the amazing falls against the crisp rocks, and the golden hour sun is beautifully lighting up the mountaintop.

In the 2nd one you can almost taste the frost from the frozen lake. The air is so crisp and clear that you can see several layers through the trunks of the trees. If you hadn’t already seen the gold in the mountains, the 2nd picture would be OK.

The 3rd is in between…not as on fire, not as clear through the tree trunks…dark in fact. The falls don’t stand out as sharply against the rocks.

By now you may have guessed, the 3rd one is the one that the artist created. The difference in the three is entirely the level of Contrast.

Low Contrast


So. What is Contrast?

Simply, in the cinema, there is a level of white and a level of black. Outside, on a sunny day, the level of bright can be 30,000 or perhaps up to 120,000 at the brightest day at the brightest time in the brightest place…and reflections on cars…they can be 10’s of thousands of bright too! And, the level of black? Wow, a dark night sky in a forest when you can’t see the hand in front of your face – a single candle will seem very bright indeed. Let’s call a candle at arms length 1. Move the candle away and it becomes .1 and .01 and .001. In theory, our eyes can still see that candle on a perfectly dark and clear night when it is many miles (or kilometers) away.

Move the candle close to you, or put several candles in your hand…or a light that has the power of several hundred candles …well, at some point you get too much light in your eyes and, in protection, they shut. And inside the eyes, in protection, there is a protection mechanism as well.

But let’s not get off the point: Contrast is the difference between the highest level of bright and the lowest level of dark. If black is 1 and white is 2,000, then we say the contrast is 2000 to 1. It is written like this – 2000:1. When it is written like that, it is called the Contrast Ratio.

Why do you need to know that?

You want to have a good feeling about your ability to notice good and bad contrast. And, most importantly, how to tell the technician what you see when there is a problem.

We give a little more detail about these things in Part 2, with more examples.


But first, take a break. The exercise for this lesson is to look in shadows while you are living life.

Notice: there are important details to see in the shadows. Look under tables. Look into the dark and notice how colors shift down to black. You might have to purposely shade your eyes from a bright light.

And: Notice how there are things to see even in light that is almost too bright to look at. The colors will be softer in bright light, even for the same shoe or car or face that was a deep rich color when you saw it in the dark.


When you have experience and a good feeling for these ideas of Contras, click into Contrast – Part 2

Photo by Rodrigo Soares on Unsplash