Why does my camera have ISO, and what is it's purpose?

   Welcome everybody! Ready for the next step in knowing your camera and the components needed to create an image? Ready to take that thing off of "auto pilot" and grab the controls in "manual mode"? ALMOST! I know.... I have some seasoned shooters following who already are shooting manual who are probably just waiting to see if I can explain how without confusing people completely. At the bottom of each article, there's a place where you can post a question. If you don't fully grasp the message.... don't be shy and ask.
   ISO.... you've all seen it and heard of it probably. I should have taken a minute to look up on Google what "I.S.O." stands for, but these segments are being composed off the top of my head without borrowing others info. First one to comment the answer, gets a prize:)  I would guess "Image Sensor Output", but regardless... ISO is all you need to know.
    Back to the human eye... and NO I'm not an eye specialist. So if YOU are, please don't try to teach me anatomy LOL. What ISO means to me is "Optic nerve". ISO refers to the sensitivity level of your camera's sensor, which is where all the light let in through the lense gets collected. The ISO button is on the back of your camera, and if you push it in any of the manual modes (above the green rectangle on your selection dial) you will see numbers come up on your screen starting at 100 and going much higher such as 100-5600 (or higher). You can thumb your arrows left and right to highlight the ISO you want, and hit "set" in the center to save your selection.
     The numbers on the ISO chart indicate the sensitivity level of your camera's sensor as I mentioned. The low number is the least sensitive and the high numbers are most sensitive. Why?  It's obvious... if you have less light, you can compensate for it by increasing your ISO resulting in a brighter image because the sensitivity of your image sensor is now higher. If there's plenty of light for your image, you can easily go with the lowest ISO setting. The sensor doesn't need to be so sensitive if there's a reasonable amount of light hitting it.
     So... ISO can make the picture brighter or darker. Isn't that the same thing shutter speed does? Isn't that the same thing aperture changes do? Yep.... but NO!!!!!!! As I mentioned before in the aperture article, there are bi-products that are good or bad with each camera adjustment you make. With ISO, it's digital noise! The higher you go, the more noise (grainey) the picture will become. My personal goal is to use the lowest ISO setting I can get away with keeping my images crisp.
    Confusing... I know it is. But to shoot in manual mode, you MUST know what each of your settings do.
Here's an example of high ISO noise: Go into a dim room (not dark/blackened) with a cell phone that has NO flash. Just rely on the lights in the room and take a pic of yourself. Looks good on the phone, yes? Put it on the computer and look at it bigger. You will see a grainey image that really looks pretty crappy. Because there was no flash to assist, the room was not bright and the phone shoots in auto mode.... it automatically chose the ISO option to correct the low light condition. Your phone chose a high ISO which did allow an image to be captured, but it's grainey!
     90% of the time I am shooting a human subject rather than landscapes. I personally RARELY shoot higher than ISO 200. I prefer to keep the ISO lower resulting in a bit darker image sometimes... and bringing in the off-camera lighting to get my subject lit up. Photoshop (even the basic cheap programs) offers solutions that will brighten your background to a more appropriate level. I can live with a little "noise" in the background, but NOT on my model.
     Fear not!!! Soon we will be discussing everything that you'll need to know to do it like the pro's. In a couple of days I will recap all of the manual settings that we have discussed. But even better, I will list how each setting affects another as well as the "good's" and "bad's" that happen with each. But before that.... one last thing....White Balance. No worries.... that's an easy one ;)

~Tommy Post
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