Understanding ISO
lesson no 7 – ISO camera settings
Background
ISO is the third component of the exposure which closes the triangle together with Aperture and shutter speed. We have covered the first 2 in the previous tutorials and we would assume you are already familiar with those. One important difference is that Aperture and Shutter speed will have a mode of shooting associated with them, Aperture Priority Mode and Time Priority Mode, where you can set up one of them and let camera choose the other. ISO is different, it does not have a specific mode, but you have the choice of setting up the ISO manually as a automatic or select a specific ISO
Let’s remember the general rule for the ISO and exposure
for each ISO (100, 200, 400 etc) there is a specific relation between the shutter speed and aperture to make up
ISO is the basis where I should start choosing the camera settings.
Definition
ISO stands for International Standards for Organisation, which in this case is not as obvious for what it does. Let’s ignore the terminology for the time being. ISO is the SENSITIVITY of the sensor and it translates HOW FAST IS THE SENSOR RECORDING – SENSOR SPEED. Not to be confused with the shutter speed
Let’s imagine an old cassette recording music.they used to have a specific speed and it does not matter how fast the singer sings, the speed of the tape is constant. There is a speed of recording for each ISO setting and the greater the speed, the faster an image is recorded onto the sensor
If the speed of recording is suited also to the time when the shutter is open, we are going to get a good exposed photo. If not, we won’t get it.
When and why
ISO or the speed of sensor recording helps in low light situations where there is not enough light for the shutter speed and aperture to expose the image correctly. Probably the aperture would be at maximum size, and the shutter speed will be longer. However, we might want the shutter speed to be shorter in order to get a sharper image and that is why, ISO is the tool to do that. By increasing the ISO we relax the requirements for the shutter speed and aperture, however is comes with a compromise. Please see the tutorial of “understanding camera” for a refresher in order to have the following information very clear:
the greater the ISO, the less quality of the picture. The sensor captures photons, in a specific time. Asking the sensor to work faster is allowing it to get less photons for the image. The speed of photons is a constant and we are willing to accept an image with less photons, , so less clear pixels. The camera will estimate the missing pixels through other methods and that is why we end up with “GRAIN”.
Do not get scared as today the latest digital cameras are doing a pretty good job and in high resolutions will compensate for that.
just recapping: the greater the ISO, the more grain we are going to get. ISO us measured in increments from 100, 125, 160,200 and so on up to 6400, 12800 and even above that for the newest camera models
As a professional photographer I am trying to stay under 1000 as the image becomes to grainy and I am not happy with that. But depending on the situation and the quality expectations a 3200 or 6400 will do the job just fine.
Exercise
in the Academy of Photography spirit we would like to propose 2 tests for you to do in order to understand how ISO is on your camera as the best way to learn for yourself. they are both in low light conditions
test 1 – ISO in automatic mode
set up the camera in fully automatic mode, and take one shot for each ISO increment starting with 100. An example is below:
Automatic mode – ISO 100 – (the exposure selected by the camera – aperture 2.8 and 3 seconds shutter speed)
Automatic mode – ISO 200 – (the exposure selected by the camera – aperture 2.8 and 1.5 seconds shutter speed)
Automatic mode – ISO 400 – (the exposure selected by the camera – aperture 2.8 and 1 second shutter speed)
Automatic mode – ISO 500 (the exposure selected by the camera – aperture 2.8 and 0.3 seconds shutter speed)
Automatic mode – ISO 640 – (the exposure selected by the camera – aperture 2.8 and 0.7 seconds shutter speed)
Automatic mode – ISO 800 (the exposure selected by the camera – aperture 2.8 and 0.5 seconds shutter speed)
Automatic mode – ISO 1000 (the exposure selected by the camera – aperture 2.8 and 1/4 seconds shutter speed)
Automatic mode – ISO 1500 (the exposure selected by the camera – aperture 2.8 and 1/6 seconds shutter speed)
Automatic mode – ISO 2000 (the exposure selected by the camera – aperture 2.8 and 1/8 seconds shutter speed)
Automatic mode – ISO 2500 (the exposure selected by the camera – aperture 2.8 and 1/10 seconds shutter speed)
Automatic mode – ISO 3200 (the exposure selected by the camera – aperture 2.8 and 1/15 seconds shutter speed)
Automatic mode – ISO 5000 (the exposure selected by the camera – aperture 2.8 and 1/20 seconds shutter speed)
Automatic mode – ISO 6400 (the exposure selected by the camera – aperture 2.8 and 1/30 seconds shutter speed)
As you can see above there is no difference in between the images as these images are taken, but the time is getting faster.
test2- ISO in manual mode with a set time and aperture
we are going to select a specific time and a specific aperture and see how the results changes by changing the ISO only
ISO 100 – (manual mode – 1 second, F2.8)
ISO 200 – (manual mode – 1 second, F2.8)
ISO 400 – (manual mode – 1 second, F2.8)
ISO 500- (manual mode – 1 second, F2.8)
ISO 640 – (manual mode – 1 second, F2.8)
ISO 800- (manual mode – 1 second, F2.8)
ISO 1000 – (manual mode – 1 second, F2.8)
ISO 1500 – (manual mode – 1 second, F2.8)
ISO 2000 – (manual mode – 1 second, F2.8)
ISO 2500 – (manual mode – 1 second, F2.8)
ISO 3200 – (manual mode – 1 second, F2.8)
ISO 4000- (manual mode – 1 second, F2.8)
ISO 6400 – (manual mode – 1 second, F2.8)
As you can see above in this case, ISO will hep the image getting more and more exposed. Somewhere in the middle is the correct exposure and we are going form an underexposed image to a significantly overexposed one.
Conclusion
For the first test the obvious question what is really the quality difference?
I guess the answer lies in the enlargement. you will notice a decrease in quality and a grain when the ISO increases. The won’t matter if you are not enlarging your images however that might be the case and you will have to accept that.
ISO 100
ISO 6400
An solution to overcome that issue is to increase the exposure time keeping the IO to a low level, but that might trigger other issue for the moving object.
In conclusion ISO can be used as a good tool to enable to shooter in low light to use faster shutter speeds in low light condition. The amount of compromise both will be the choice of the photographer
ISO camera settings
// ]]>
…………..
// ]]>
The post ISO tutorials – camera sensor sensitivity and settings appeared first on Academy of Photography.