Over the past few weeks in Exposure 1, Exposure 2 and Exposure 3 I have written about the subject from a theoretical point of view, but how does all that translate to the real world when you are new to photography?
I figure it is worth a practical walkthrough that will help beginners get a handle on shooting with a DSLR, without relying upon the auto functions of their camera to save their bacon.
It’s been a while, but I am picking up on the discussion I started a while ago, in relation to exposure.
As a quick recap, in Exposure – Part 1, we covered the concept of exposure and how it relates to the histogram you see on the back of your camera.
In Exposure – Part 2, we addressed aperture, and how it impacts on exposure. We also learned about the tradeoffs that occur when we choose an aperture.
In this post, we will deal with shutter speed and ISO.
Using the tap analogy from the last post, Shutter speed is how long you leave the tap turned on:
Now that we have decided what aperture we are going to use, to fill our theoretical glass we would need to turn the tap on, wait until the glass fills up, then turn the tap off again. In camera terms, this is done by setting the shutter speed (how long the shutter stays open to let light come through the lens and onto the sensor).
Shutter speed is usually measured in fractions of a second. While some exposures might go for many second, minutes or hours, most people will play quite happily in a range from, say, 1/20th of a second (a long exposure) to as high as 1/2000th of a second ( a very fast exposure).
The trade offs with shutter speed are related to artistic objective and sharpness. The shorter that my shutter is open, the less subject movement I get, but the wider my aperture needs to be so that I get enough light in. IF I am taking a picture of children running around, I might want a fast shutter speed to freeze them in action and show their features in sharp detail. Or, I might choose a slower shutter speed that will allow for some blur, to portray a sense of motion. Either is acceptable depending on your artistic objective.
ISO is the size of your glass:
Lastly, think of ISO (which is really a term for the sensitivity of the sensor to the light that is coming though the lens) as the size of the glass. If you choose a tall glass (equivalent to a low ISO), no matter how wide you open the tap it will take longer to fill the glass (Get a good exposure). If you choose a small glass (a higher ISO) you can fill it with less water for the same tap (aperture) opening.
So what’s all this about trade offs?
OK, if you have managed to grasp the concept of the glass of water, we can move on. When I say there are trade offs, let me explain in as simple a way as I can:
When you choose an aperture setting based on how you want your image to look, you will then need to choose you ISO and shutter speeds to make sure that you get a good exposure. Here are some examples, to help you relate:
In the above indoor shot, I wanted a shallow depth of field to blur the background, so I chose a wide aperture. But my subjects was constantly moving, so I needed a reasonably fast shutter speed to get a sharp image. As a trade off, I needed to select a high ISO to prevent subject motion blur. the trade off was image noise (graininess). For interest, My settings were Aperture f1.8, Shutter speed 1/125th second and ISO 800
Alternatively, in the above outdoor shot, I was outside on a bright day, and I wanted a shallow depth of field while freezing the motion of the drummer’s hands. I choose f3.5 to give the right depth of field, together with a shutter speed of 1/2500th of a second. Because it was very bright, I was able to keep my ISO low, so I have a good quality image with little noise.
I realise this gets a bit confusing, so I have put together a table below that summarises the three settings and the trade-offs we have discussed:
Breaking the “Rules” with Exposure – Bonus Points if you read this part:
Now that you have an appreciation of the basics of exposure, let me throw in a curve ball – here are two more images that are well exposed:
How can these two be “well exposed”? The answer lies in my intent. There are no set rules about what is properly exposed, as long as the image communicates what you want it to say. What you will notice about these two images is that the parts of the image that I wanted you to see have good tonal detail. You can see what you need to see without loss of detail or bad image quality. In the case of the first, I wanted a high key, washed out effect. In the second I was happy to allow the shadows to disappear into black.
Ok, it’s a lame topic heading, I know. But interweb, I am keen to tell you that I am moving to a newer, better, brighter and shinier domain!
While www.lineofsight.white-lite.net has been a great place to start up my website and play with it, there are some compelling reasons to make things a bit cleaner and more streamlined.
So as of tonight, my photography website and blog have moved to www.shaneambry.com, which I am sure you will agree has a nice, cohesive feel to it. In fact, I like the domain name so much, maybe I’ll change my name by deed poll to match it…. 8-P
I have also tidied up the navigation bar on the right hand side of the blog, so it’s a bit easier to find the things that you want.
If you have an RSS feed (yes Mum, that means you), then I suggest that you pick up the new one from the bottom right hand side of the blog page.
And in case you forget, don’t despair, I’ll be placing an automated re-direction on the old address, so you’ll automatically be forwarded on.
So I hope to see you on the other side!
My son, the long suffering test subject – he thinks it’s boring and would rather be playing with his trains.
Love you, Buddy.
