Understanding Exposure part 5

It goes without saying that if you’re here at part 5 and you haven’t started at part 1… you are not getting the full picture (pardon the pun).

I get so many questions on how to use your camera on MANUAL or at least not on AUTO I decided I had better create a small guide. I call it the Bermuda Triangle of photography, because it is where EVERYONE gets lost… you know, we start talking about f-stops, shutter speeds and ISO and the likes, and maybe even throw in something about histograms and that big numbers are small apertures and small numbers are wide open and 1 stop down halves our light etc, etc, etc… are you scratching your head yet…? if all of this is mumbo jumbo to you then you definitely need to read parts 1 to 4 first! Got it!

Here are the links to the previous 4 parts

Part 1 – the overview

Part 2 – buckets and other stuff

Part 3 – auto no more

Part 4 – what the f-stop

By now I would expect you to have a fairly basic but good solid understanding of exposure. So far you have learnt that your sensor needs a certain amount of light to get a correct exposure, and if you slow down your shutter speed you need to let less light in or you will overexpose, and if you speed up your shutter speed you need more light…

Today we’re going to look at using your histogram and ISO. All of the info in the last 4 parts assumes you have a correct exposure, to ensure you actually have a properly exposed image you need to understand how to use your histogram. In some cases you can just look at your LCD preview screen on the back of your camera and it is obviously too dark or too bright. Unfortunately, these screens are not fool proof and don’t tell you accurately enough whether or not your pic is properly exposed.  Looking at your histogram will give you more accurate information.

If your image is under exposed, the histogram will be all bunched up on the left edge…

Under Exposed Image

If you’re image is over exposed, it will be bunched up on the right edge…

Over Exposed Image

A correctly exposed will have none of the histogram on either edge…

Correctly Exposed Image

If you’re not sure where to find your histogram you will need to get your instruction book out… every camera is different but most make the histogram easy to find from the photo preview screen.

Now you understand how to make sure you have a correctly exposed image, you can control your shutter speed and aperture and make creative decisions for yourself!

It is time for us to have a quick chat about ISO… let’s say you’re in a rock concert, and you want to take a photo of the lead singer as he is jumping around the stage, the stage lighting is dim and you know you need a relatively fast shutter speed otherwise the lead singer will just become one big blur… you put your camera on aperture priority and you open up your aperture to the maximum you can, say f3.5 on your lens, and you take a shot, using your histogram you can see that you have the perfect exposure… but… it is all blurry! You can’t even make out who or what it is in the picture…

Your new best friend is ISO… ISO controls the sensitivity of your cameras sensor, the higher the ISO the more sensitive to light your sensor is… the downside of a higher ISO is it creates what is called ‘noise’, noise is a visible grain in your photo, and the higher your ISO the more you will see it. I ask you this one question…. would you like a blurry or noisy photo?

Increase your ISO from 200 to 400, you have doubled your sensors sensitivity so you can now increase your shutter speed by double too… go from 400 to 800 ISO and you can double everything again… my camera will go up to ISO6400 before the noise gets totally unacceptable… Every camera is different in how well it handles noise, and there is plenty of software that will help you remove noise form your pictures once you have them downloaded to your PC.

Now go out and shoot some pics… the best way to learn is to practice!

The Daily Pic – Tall Timbers

I have driven past this spot several times and every time I did I wanted to stop and get a photo. I am going to get one from each season, so this is the leafless winter shot…. I will be back in spring, summer and then the spectacular autumn colours to round off the series!

Tall Timber

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