You're Smarter Than Your Camera - ISO - Help Shutter speed and Aperture are Just not Enough!!!
Good morning and welcome to the 10th blog on 'You're Smarter Than Your Camera'. Wow....and congratulations, you have made it to your 10th blog and you can be sure your understanding of your camera is improving!!
This week we look at what we can do to get a little more out of the camera when you are struggling with the settings we have already talked lots about - shutter speed and aperture. The setting is ISO and we will also touch on the negative aspects of increasing ISO.
The May blog will also look at how lenses can affect the light entering the camera and how to make some sense out of the histogram - your best friend for assessing exactly how exposed your image is. More advanced topics will detail different types of noise and touch on some of the development and creative effects that can help to manipulate it.
Thanks for reading and hope your continuing to enjoy my blog...do get in touch in you have any comments or suggestions, or would just like to share your experience so far.
ISO - The Introduction
There are situations where we stretch the capabilities of our camera, where we want to get great shots, but the lighting isn't very good or the subject is moving too quickly or we want to get a greater depth of field in a landscape image. These are all examples of when shutter speed and aperture alone may not give us the image we want. For example we want a high shutter speed (reduces the light entering the camera) because our subject is doing sports, we are happy with a shallow depth of field (increases the light entering the camera) but that isn't enough, the light sensor is telling us that the image will be way underexposed! Help, what can we do?!!
Enter the ISO setting. This is the third and final setting on your camera that controls the amount of light that creates the image. Unlike aperture and shutter speed it doesn't change the actual amount of light entering the camera, but rather controls the sensitivity of the sensor. Remember the films days in which we used to be able to buy films with different ASA speed??? 100, 200, 400 it was an indication of the sensitivity of the film. The equivalent with digital cameras is ISO.
ISO - So What Does it Mean?
Normal ISO ranges from 200 to 1600, but today's digital cameras can go as low as 50 or as high as 204,800 (~www.nikonusa.com), not sure if you would be able to detect the subject from the noise in that high setting - I'd like to see it!!
Low ISOs such as 100 or 200 are most commonly used in good light situations. Where the light is limited or you don't have access to a tripod, higher settings need to be used. Each time you double the ISO (i.e. from 100 to 200) the camera only needs half as much light to create the same exposure.
Great! So we are able to create images in lower light situations, well yes and no. The impact of increasing the ISO on the image is that 'noise' is created, and it's funny that the 'faster' films for the pre-digital camera's also had the same problem - 'film grain'. Cameras today can go up to high levels of ISO without compromising the image too much; 1600 and above is often used.
Below is an image of my Nikon D7000 and how to change the ISO, you may have to go through a menu setting to change it depending upon your camera.
Just in Case You're Curious - Why is it Called ISO?
ISO actually started out as ASA (American Standards Association). In the film days a commercial film manufacturer created a set of numbers that represented the sensitivity of different types of film. The set of numbers were accepted by the ASA so that all US manufacturers could use the same standard. This was then adopted by the ISO (International Standards Organisation) and ASA became ISO.
So How do I set it?
Basically, in good light situations you want a low ISO - 100 or 200, but in low light situations you may want to increase it - see my drawing below.
You may think that ISO is equivalent to aperture and shutter speed and should be adjusted with the same frequency as them. This isn't the case....ISO is the goto or the 'wildcard' in your hand, if you can't get the exposure you want from shutter speed and aperture settings. If you can, then you shouldn't adjust ISO at all.
Ok so you're on your way to mastering aperture and shutter speed or at least you understand the concept. Continue with your camera on the manual setting (auto focus) and try to create a situation where you are challenging the limits of your camera. I.e. choose a subject - lets say a sunset. First you probably want a fairly small aperture (high f number) to allow most of the scene to be in focus, lets say f16. Second, you don't have a tripod and so can't go below the shutter speed that you can hold manually, lets say 1/60. Now, depending upon how much light there is, your camera may be telling you that your image will be underexposed. Change the ISO and take a variety of shots with different ISOs to see the effect it has on your image and exposure.
Next week we will get into how to figure out the exposure of your image using the histogram, sometimes (actually most of the time) the LCD screen is just not good enough. I will also go into more detail about the effects of increasing the ISO.
Until then, thanks for reading and enjoy your photography :-)
As always, I would love to hear any comments or questions you have.