"low light"

What are ISO numbers? Lesson 6



A Definition:

The ISO number = how sensitive the camera is to light

“The lower the number the lower the sensitivity of the film 
and the finer the grain in the shots you’re taking.”  
- Darren Rowse

There are 3 basic variables that are part of the process of taking a picture. We talked about the first two variables in Lesson 4 and Lesson 5 – the camera’s aperture and shutter speed. The last variable we will talk about is the ISO.

Can you remember waaay back to the film days before basically everything went digital? (I wasn’t even taking pictures back then!) Anyway, when people bought their film, they had to choose what light sensitivity they wanted – what ISO number to choose. The higher the number, the more sensitive the film was to the light. People chose a higher speed film such as ISO 800 for use indoors and bought a lower speed film like ISO 200 to use outside.

Of course, nowadays most people have digital cameras and therefore don’t use film, but changing the ISO according to your circumstances is still important. There’s no reason not to! It’s so much easier than changing film!

Q: Why not just use ISO 800 (or another high ISO number) all the time? After all, it’s more sensitive to light!

A: The higher the ISO number, the grainier, “noisier” and lower the quality of the resulting image. The lower the ISO speed, the better the quality and the less grainy or noisy the picture is.

 



This is the view at 100% of part of a picture that was taken using a high ISO number. You can see the grain and noise, can't you?




Here is a view zoomed in at 100% of part of a picture taken at a low ISO number. The picture details are much cleaner and clearer in this shot.









Here is the total picture. The place where the 100% crop was taken from is circled in red.
The more you spend to buy a camera, the better it will perform at higher ISO numbers. (Point and shoot cameras are especially prone to noise and grain, even when the ISO number is only sort of high!)




The camera’s aperture, shutter speed, and ISO all word together. You can change any one of these and the exposure will change (the picture will turn out lighter or darker) if the camera is set to M (manual mode). For the other camera modes, the camera compensates for the changes you make to any of these settings.

Look at the three variables - aperture number, shutter speed, and ISO number - as if they are 3 crucial ingredients in a cake. If you change one of them the picture will turn out differently.


In the photo on the left, I used an aperture of f/3.5, and a shutter speed of 1/250 sec. at ISO 200.

In the photo on the right, I used an aperture number of f/3.5 and a shutter speed of 1/1500 sec. at ISO 800. By having the ISO number at 800 instead of 200, I could raise the shutter speed. (not that I needed to in this instance!)
Even though the settings are different, the picture can still turn out basically the same. The only difference is the lower quality of the one that was taken at ISO 800 (When an 8x10 print is made of each image, the difference in quality is much more apparent.)

 





For this picture, I changed the aperture number to f/19. This meant that the shutter speed or ISO number had to change also. Since I didn't want to raise the ISO number any higher than 800, I used a longer shutter speed - 1/45 second - to let in more light and compensate for aperture number I chose.








Do you see in these pictures that in order to get the same exposure (same brightness of the image) if I change the aperture, the shutter speed changes. If I change the shutter speed, the aperture changes too. If I change the ISO, either the shutter speed or the aperture (or both) have to change also.

Q: How do I know what camera mode to use and what settings to adjust?

A: This depends on what you want the final picture to look like. Let me explain.
  • If the background in the image needs to be out of focus, set the camera to Av (aperture priority mode) and set the aperture to a small aperture number for a small amount of the picture to be sharp. The camera will adjust the shutter speed for you.


  • If you are after the dreamy, soft feel of a slow shutter speed, set the camera to Tv (time value) and select a slow shutter speed. The camera will then adjust the aperture to get the correct exposure – not too bright and not too dark.


  • If you are in a dim environment and need the camera be more sensitive to the light, know that the picture quality will suffer somewhat when you boost the ISO number, but boosting the ISO number will enable you to take a picture that otherwise might have been impossible to capture.


A Review:

  1. If you used to use a film camera, bumping up the ISO is the equivalent of putting in a higher speed of film
  2. Low light – in situations where the light levels are very dim and you can’t use a lower shutter speed or bigger aperture to let in more light, boost your ISO
  3. A higher ISO number makes the camera more sensitive to light
  4. A high ISO number does degrade the image quality –  it makes the picture more noisy or grainy
  5. Don’t pick a higher ISO number than is needed.
  6. The lower the ISO, the better, but make sure not to get a blurry picture!


“Whoso offereth praise glorifieth me: 
and to him that ordereth his conversation aright will I shew the salvation of God.”

Psalm 50:23

Controlling the Camera’s Shutter Speed: Lesson 5

The shutter speed you select controls how long the camera’s shutter is open letting in light and making the picture.

Why should you learn how to control the shutter speed?
  1. Be able to set a shutter speed high enough not to get blurry pictures at low light levels
  2. Be able to create all kinds of pictures that show movement.

Camera Mode to use: Tv (time value) – controls the shutter speed


In your camera, the shutter speeds looks something like this: 1/60 (the shutter is open for one sixtieth of a second), or this: 1/200 (the shutter is open for one two hundredth of a second), etc.

Regularly, the goal when taking pictures is to freeze a moment in time forever. If the room is dark or the lights are dim, the camera will often set a slow shutter speed, motion will not be frozen, and you will be left with a blurry picture and only a mental picture of how cute baby Anna Marie or little Timmy looked.

There are two types of motion that have to be compensated for: your shaking hands and the movement of your subjects.

For shaking hands – and everybody’s hands shake at least a little! – If your camera has something called IS (Canon), VR (Nikon), or OS (Sigma), use it!

Image Stabilization (IS) or Vibration Reduction (VR) or whatever you want to call it (!) is very helpful in compensating for small jiggles on your part, but does nothing to fix the blur of your dog dashing towards you or any other movement in the scene apart from your movement. Bracing your hands or camera against something solid or using a tripod also helps reduce or eliminate blurriness from your hand movements.  Remember that what is needed to fix the blur of a dog running past you is a high shutter speed.



I’m sure you’ve all seen pictures of water – rushing through rocks, and in streams, rivers and waterfalls. When photographing water, you have a choice to make. Either pick a high shutter speed (1/2000 of a second) and capture each water droplet as it is sprayed into the air, freezing the moment, OR pick a slow shutter speed (1/2 to 2 seconds depending on how fast the water is flowing) and capture the silky smooth, painterly motion of the water.

For these fun shots, the girl or boy had to stand VERY still for several seconds and then duck out of the picture quickly at my signal for the rest of the exposure time (the camera was on a tripod). The effect turns out different every time! (If needed, the faces can be lit with a weak flash light from off to the side of the camera, but be careful not to hurt their eyes!) I took these pictures several years ago when I was first learning to control my shutter speed. :) 



In this photo, I wanted to take a picture of this tiny toy in a dramatic way. The problem: it was dark and it was evening. So, I picked up a flashlight and BAM! I had dramatic lighting. All I had to do was set the camera on a solid surface, set the 2 second delay timer, and keep the flashlight shining on the truck. The shutter speed was 1/8 second. One other important point: Remember to set the exposure compensation if you’re taking a picture of a dark scene and don’t want the blacks to end up as grays. Here, I set my exposure compensation to -1.

An Interesting Thought:

When taking a picture...
A small aperture number and a shorter shutter speed = A big aperture number and a longer shutter speed

Some general guidelines:

  1. Check your pictures for blur, especially indoors or at twilight. If they’re blurry, boost the shutter speed!
  2. If you have very steady hands, you’ll be able to handhold your camera at much slower shutter speeds than those whose hands aren't super steady. Experiment to find out how low you can go while still getting crystal clear pictures. Keep in mind that when you are excited or rushed, you may have to set the shutter speed higher.
  3. If you can, a minimum shutter speed of 1/500 of a second is a good shutter speed to start with for freezing action. Even 1/500 doesn’t stop all action! Sometimes I have to set a shutter speed of 1/2000 of a second or even 1/4000 of a second!
  4. It’s always best to err on the safe side and choose a higher shutter speed than you think is needed (if the lighting is bright enough for you to have that option!). Better safe than sorry!


Assignment:


Go out and test your knowledge! Don’t be afraid to try anything! (We learn by making mistakes -  sometimes I wish that wasn’t so true!)

So many creative possibilities open up once you’ve learned how to control the shutter speed. I can’t even begin to cover them here. See ya later!

Have a marvelous day!

~ Laura

"And the angel answered and said unto the women, 
Fear not ye: for I know that ye seek Jesus, which was crucified. 
He is not here: for he is risen, as he said.”
Matthew 28:5-6a

I hope you all had a meaningful Resurrection Sunday!