ISO and Shutter Speed assistance

pictureperfekt · Oct 11, 2012

I am trying to understand better the relationship between the ISO and shutter speed and thought if I took some similar shots and wrote down what I had done, this might help me retain this information in my head better.

I set the ISO to 200, Aperture to 5.6 (kept it at 5.6 for all of these shots) and adjusted shutter speed to 1/320 for a correct exposure:
View attachment 22561

Than I changed the background and kept ISO 200 and adjusted shutter speed to 1/160:
View attachment 22562

Adjusted the angle of the light a little and Shutter Speed to 1/250:
View attachment 22563

On this I adjusted ISO to 100 and shutter speed to 1/320:
View attachment 22564

This exercise has helped me a little bit to think about what I am doing.
Now that I have given thought to what I have done...my question is:
Am I doing anything right?

SCraig · Oct 11, 2012

What is it that you are TRYING to do? With a scene like that changing the shutter speed and ISO is not going to show any visible difference other than some underexposure, especially with the ISO that low.

The relationship between shutter speed, ISO, **AND** aperture (all THREE are related) is that for any given exposure you cannot change one of the three without changing another to maintain the same exposure. That's why it is commonly referred to as the "Exposure Triangle".

Your first shot was ISO 200, shutter speed 1/320, f/5.6. Assume that was a "Proper" exposure.

Your second shot was ISO 200, shutter speed 1/160, f/5.6. You lowered the shutter speed 1 full stop (which allows twice as much light in during the exposure) without changing either of the other two to compensate which should have overexposed the shot by one full stop. To maintain the same exposure when you halved the shutter speed you would have needed to halve the ISO or aperture to compensate.

pictureperfekt · Oct 11, 2012

I was working with direct sunlight on different backgrounds trying to figure out the relationship between the ISO, Aperture, and Shutter Speed, and see for myself if I changed one how I would set the others to assist with a "proper" exposure.

Your second shot was ISO 200, shutter speed 1/160, f/5.6. You lowered the shutter speed 1 full stop (which allows twice as much light in during the exposure) without changing either of the other two to compensate which should have overexposed the shot by one full stop.

On the second shot I changed two things 1 - the background lighting and 2 - the shutter speed to compensate for that. I had thought that I would have had to compensate for changing the shutter speed, but saw this wasn't the case based on the amount of light that I had. Basically these shots got me to think and after them it left me thinking...Oh, I guess that makes sense.

Dao · Oct 11, 2012

Maybe you can try this.

1 Put the camera on a tripod or on a table or sandbag.
2 Put a soda can on the table about 4 to 5 feet from the camera.
3 Focus on the soda can.
4 Set ISO to 100, aperture to f/5.6 and whatever the camera meter think the shutter will be and take a shot.
5 Set the ISO to 200, keep the same aperture and change the shutter speed to half of what you use in the previous step.
6 The result exposure should be the same. (except the ISO 200 photo may have a little more digital noise)
7 Repeat step 5 with with higher ISO and faster shutter. Each time, double the ISO and cut half the time for the shutter speed.

Repeat the above and keep the shutter speed constant, vary the ISO and aperture. You may also notice the background changes with the aperture size.

2WheelPhoto · Oct 11, 2012

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Rick58 · Oct 11, 2012

I'm a confused as everyone else. It sounds like you are looking for changes due to changes of shutter speed. Shutter speed alone won't change the appearance of a static object. If you are expecting depth of field changes, you need to change your aperture (f-stop), not shutter speed.
Now, keeping your ISO constant, changing your shutter speed will require a change in f-stops to give the proper exposure. If you want more Depth of field, a slower shutter speed will allow you to use a smaller f-stop which will increase your DOF, and visa-versa.

Think of a Pie. Now cut the pie into 3 pieces. The 3 pieces become you ISO, Shutter speed and Aperture. You can't go outside of the pie, so if you take more of any one piece, you have to sacrifice something with the remaining two peices.

ISO is mainly changed according to the amount of light you are shooting at. Generally, the lower ISO you can use will result in finer photos. The higher you raise the ISO, your picture begins to lose quality. Higher ISO's will allow you to shoot in lower light. You can change the ISO to raise or lower shutter speed and aperture, but that's another lesson.

EIngerson · Oct 11, 2012

Set your camera to AV. pick an F-stop. Change the ISO and watch what happens to the shutter speed. THAT will show you the relationship between ISO and shutter speed.