AYWMC: Part 1 Technical, Lesson 4: ISO

Lesson 1.4 in my own words:

• ISO (International Standards Organisation) - a measure of sensitivity to light
• 1 of 3 options (along with aperture and shutter speed) to control the amount of light hitting the camera's sensor.
• Technical aspect: increasing ISO makes it easy to take photos in low light.
• Creative aspect: none
• Potential negative aspect: high ISO can degrade the quality of the photo.
• Changing ISO
• Auto ISO - lets the camera choose
• Manual ISO - check camera manual for instructions
• When to change ISO
• On manual shutter speed 
• long shutter speed may require a lower ISO to darken the exposure
• fast shutter speed may require a higher ISO to lighten the exposure
• On manual aperture settings 
• as depth of field increases (due to smaller aperture), more light is needed for proper exposure.
• increasing ISO is an alternative to lengthening shutter speed, which increases the risk of camera shake.

This week's project:

• Step 1
• Learn how to change your ISO manually. 
• Find out if you have Auto ISO and in which modes it works.
• Step 2
• Choose either the aperture or shutter speed exercise from lessons 2 or 3, and experiment with the ISO for each.
• Don't worry about the quality of the photo (graininess/noise). The purpose of the exercise is to begin to understand ISO through experience.

I decided to try the homework on both aperture and shutter speed. I took these photos at the largest resolution my camera offers (6000 pixels by 4000 pixels), which is way too large to display on this blog. So I resized them to 500 pixels by 333 pixels, to display the entire image. To get a closer look at image quality, I also cropped a 500x333 selection from the original photo.

I started with aperture.

Large aperture (f/5.0) and low ISO (100)

Same photo, clip from original size

Large aperture (f/5.0) and high ISO (25,600)

Same photo, clip from original size

Small aperture (f/32.0) and low ISO (100)

Same photo, clip from original size

Small aperture (f/32.0) and high ISO (25,600)

Same photo, clip from original size

Then I took a second set with different shutter speeds.

Short shutter speed (1/40 sec) and low ISO (100)

Same photo, clip from original size

Short shutter speed (1/40 sec) and high ISO (25600)

Same photo, clip from original size

Long shutter speed (1/4 sec) and low ISO (100)

Same photo, clip from original size

Long shutter speed (1/4 sec) and high ISO (25600)

Same photo, clip from original size

What I learned:

• I could definitely see the point of the lesson, that photo quality degrades with higher ISOs. 
• Since I manually controlled only two of the three things that affect exposure (aperture, shutter speed, and ISO), and the camera compensated by automatically adjusting the other one. 
• That correct exposure is a complex task and will take a lot of practice to master (or at least get half-way decent at.)
• That my camera does a really good job compensating. (So, I'm not sure I got all the subpoints of the lesson).
• I won't have to worry much about ISO for any photo I publish on the internet. Graininess can't be seen after resizing them for online use, unless I crop like I did for this exercise.
• For print photos, I'll have to take more care to avoid grainy pictures.