So, you're back? I'm taking this to mean that you had some fun yesterday and you're rearing to go to learn more? Did you try playing with the different settings, including the ISO to see what happened? Today I'll talk a bit more about ISO, then I will move on to showing some photo examples.
If you tried changing your ISO while keeping your aperture the same, you might have noticed that it affected the shutter speed. Remember on Monday I said that ISO measures light sensitivity? To explain it in practical terms you can think of ISO as your light gatherers, bringing the light into the camera. An ISO of 200 would be twice as many light gatherers as an ISO of 100. This means that you will need the aperture to be open half as long, which means your shutter speed would be half what it was at ISO 100.Still with me?
This is why you use a higher ISO in low light conditions.When the light is low, you need as many light gatherers as possible in order to use the fastest shutter speed possible, otherwise you will end up with blurry photos, (remember that a slow shutter speed can't freeze the motion and you will see motion blur). Conversely on a bright sunny day you use a low ISO such as 100 (some cameras even go as low as 64!) because with the abundance of light, you don't need as many light gatherers and you will be able to have a pretty fast shutter speed to get a correct exposure (and avoid blur).
At this point it is also useful to remind you that you also control the amount of light entering your camera with the aperture - how wide the door is open. In low light you usually want to have the lens as wide open as it will go. Ironically this corresponds to a LOW aperture number (the technical name is an f-stop but I never think in these terms so I am avoiding using it!). So you would set your aperture to the lowest it can go. This would depend on your lens. If you are using a standard kit lens the lowest available is usually 3.5, with the lens zoomed out as far as possible. My favourite 50mm lens will go as wide open as 1.8.
I urge you to take your camera and go out to practise. It takes time for this part of it to click, and it will only truly click with lots of trial and error. Believe me, I have lots of very blurry and dark photos to prove it!
Now for some examples to illustrate.
One of the ways I love to use to see the effect of changing shutter speeds is to take photos of flowing water. I do this everytime I am near to a river or stream! This summer I took these two shots.
High (fast) shutter speed
In this shot my shutter speed was 1600 (technically 1/1600) and you can see that it practically froze the water. You can almost see the drops splashing up!
In this second shot I slowed it down to 1/10 and now the movement of the water is blurred, giving that milky white appearance.
A couple weeks ago at the park Kieran amused himself by running laps around me. I just had to try to capture his enjoyment. My first few shots were a wash, with too low a shutter speed 1/60
It's kind of cool because you can definitely tell that he was moving, but it wasn't exactly what I was going for. So I upped the shutter speed to 1/160
You can still tell that he is moving, because there is still some slight blurring, but this photo really captured what I wanted.
Just so you know I took over 30 shots in this five minute period and most of them were bad. But I was able to get this awesome one in between as he flew by me and gave me a happy grin.
Totally worth it sitting there shooting like a maniac while people looked at me like I was crazy.
Here are a few examples illustrating what you should expect with changing apertures. Apart from the aperture controlling how much light gets into the lens, it also plays in role in what your background will look like. The technical term for this is Depth of Field (DoF). A wide depth of field means that pretty much everything in the shot is in focus, that's what you get with a high aperture value like 16. A narrow depth of field means that only very little is in focus - the result of a low aperture number.
In the photo on the left, with the aperture set at 6.3 most of the strawberries are in focus. In the photo on the right with the aperture set to 3.5 you can see that the starwberries towards the back are softly blurred.
Here are some photos of Kieran at the park. The aperture changes from 8.0 to 3.5 to 2.2.
Can you see how the grass in the background changes while he remains in focus? In the first photo, you can actually make out blades of grass, but not in the last one. And in case you're wondering my other settings were: ISO 200, White Balance - Shade, and Shutter Speeds 1/80, 1/320 and 1/800 respectively.
So, still with me? Now it's your turn to go and play some more! Tomorrow I will share some of my tips for shooting in various circumstances, including everyday shots and events. Is there an area you'd like me touch on? let me know in the comments! And as always feel free to ask any questions you might have.