Tuesday, July 16, 2019

Lesson 2 - Cameras & Lenses - Part 2

It's been a while since my last post, been busy building a website. However, here is more info.

All cameras have at least three things in common; film/sensor, aperture, and shutter speed. Let's take a look at each:

FILM and/or SENSOR - each film or digital sensor has a rating established by the film or camera manufacturer. This rating is commonly called the ISO rating of each. These letters stand for the International Organization for Standardization, the group that has classified film/sensor ratings since the late 1980's. 

With film, which I use exclusively, the ISO is built into the film as its produced. The ISO of a digital camera is a setting that's within the camera and can be changed by the photographer as seen fit for any particular image. 

The higher the ISO, say ISO 3200, the more that rating is sensitive to light. It will take less time and light to get a proper exposure. Typical setting for night photography for example. ISO 25, on the other hand, is the exact opposite. This setting requires more time and light to achieve a correct exposure. You might well need a tripod to create an image using the low ISO rating, also called ISO speed by some. Your best mage at this rating would be bright light outdoors.

The most common ISO ratings are 50, 100, 200, 400, 800, 1600, and 3200. You'll notice that each number is twice or half the other. For example, ISO 200 has twice the "speed" of ISO 100 meaning less light/less time for a proper exposure, half as much. In other words, if a good exposure at ISO 100 takes 2 seconds of time, at ISO 200 it would only take 1 second. Likewise, ISO 1600 is twice as slow as ISO 3200. A good exposure using ISO 3200 at 1 second would mean an exposure of 2 seconds at ISO 1600. Can seem a little confusing but once you get in the habit taking your own meter readings, instead of shooting "automatic-let the camera do it", you'll become very familiar with the ISO ratios.

APERTURE - this term refers to how much or how little you open the diaphragm that's built into each lens. The diaphragm typically has metal leaves that open or close as you set your f stop. This terms refers to focal, as I understand it, but more than the name is the function. 

Picture if you will the human eye. When exposed to bright light, your eye closes down and in the dark, it opens up to constantly control the amount of light you see. Another way to look at it is to think of a faucet. The more you open it, the greater the water flow. When you shut it down, you get less water. Your control of the f stops does the same thing in your camera. 

These f stop settings can be most often found on the exterior barrel of your lens. The full line of f stops is f/1, f/1.4,  f/2,  f/2.8,  f/4,  f/5.6,  f/8,  f/11,  f/16,  f/22,  f/32,  f/44,  f/64. Most modern day cameras have a range of f/2.8 through f/16 or f/22. Important fact for you to always remember is that the lower f stop you choose, the greater the diaphragm opening (more light/"water") and the higher the f stop number, the less light is passed through. 

Think of it this way, at f/1.4, your aperture is a big as a half dollar, let's say, while at f/64, your aperture is barely a pin hole. Critical principle, opening up one full f stop ( f/11 to f/8 ) doubles the amount of light entering the camera while closing down one full f stop ( f/16 to f/22 ) cuts the light in half. Numbers going down, more light. Numbers going up, less light.

SHUTTER SPEED - this term refers to the amount of time your camera shutter remains open allowing the light to come through the f stop you chose and then ending at the film our sensor within your camera. This timing can be in minutes, seconds, or fractions of a second depending upon the limitations of your particular camera. Many cameras today can give you multiple minutes of shutter speed and as quick as 1/1000's of a second or even faster. 

There is a shutter speed dial on most every camera that allows you to choose the speed you wish. The speeds can be 1 second,  1/2,  1/4,  1/8,  1/15,  1/30,  1/60,  1/125,  1/250,  1/500, and 1/1000 of a second. Of course, many cameras have a slower speed than 1 second and a faster speed than 1/1000 of a second but the key thing to remember is the ratios again. Just like ISO and APERTURE, shutter speeds have the same relationship. Slower the speed, the more time light has to enter the camera. Faster shutter speeds reduce that amount of time. Each speed is either twice that of another or it's half.

Now let's do a hypothetical case to show the correlation of ISO, aperture, and shutter:

1) We'll use ISO 200 either by buying that film or setting our digital camera as such
2) We'll take a meter reading in bright sunlight at a park, meter set to ISO 200
3) Metering reading equals:  ISO 200 - f/16 (aperture) - 1/250 (shutter speed)
4) We set our camera to ISO 200 (film/sensor) - lens to f/16 - set speed dial to 1/250
5) Great shot - good exposure

Now let's change things a little leaving ISO 200 the same: 

1) We get the exact same shot by choosing f/11 @ 1/500 (more light, faster speed)
2) We get the exact same shot by choosing f/22 @ 1/125 (less light, slower speed)
3) If we change the ISO (faster/slower) we get the exact same shot by adjusting the f stop/speed 

I trust this information will prove helpful for you. Thanks for stopping by!


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