Exercise 29: Higher and lower sensitivity

This exercise is regarding noise and involves taking shots at both normal and high sensitivity.  The course notes suggested choosing a situation which is marginal, where the mixture of light level and subject movement or depth of field is only just possible.  It suggests a busy street market on an overcast day.  My day started overcast but 'unfortunately' the sun came out half way through my shoot.

I have converted all images to black and white as I think you can see the noise in the image more clearly.

My Canon 5DMkII has noise reduction software and I forgot to turn this off.

Photograph 1: ISO 100

Canon EF85mm f/1.8 USM Lens, 85mm, f/5.6, 1/100s, ISO 100

This image is sharp with no loss of detail in the dark or light areas.

Photograph 2: ISO 160

Canon EF85mm f/1.8 USM Lens, 85mm, f/5.6, 1/100s, ISO 160

Again this image is sharp with little or no noise.  I needed to greatly increase the ISO!

Photograph 3: ISO 640

Canon EF85mm f/1.8 USM Lens, 85mm, f/5.6, 1/400s, ISO 640

As you can see CMOS sensor in my Canon 5DMkII is excellent (I also had noise reduction still turned on).  However, I can start to see some noise in the shadow areas.

Photograph 4: ISO 1250

Canon EF85mm f/1.8 USM Lens, 85mm, f/5.6, 1/1250s, ISO 1250

Even at ISO 1250 the canon files are still sharp with very little amount of noise in the shadow and darker areas.  These images were however much easier to shoot and freeze the action as a shorter shutter speed was required.

Photograph 5: ISO 1600

Canon EF85mm f/1.8 USM Lens, 85mm, f/5.6, 1/80s, ISO 1600

I moved inside to try and make the sensor work harder and increased the ISO to 1600. As you can see there is quite a lot more noise in this image especially in the shadow areas of the faces.

Digital noise appears on digital files as random, unrelated pixels, often of bright colours (whites).  Noise is often seen or more prevalent in shadow areas and degrades image quality.  Digital noise is caused by the heat generated by the sensor, which can be most noticeable during long exposures and by the process of amplification used to increase the light signal at higher ISO ratings.  

The easiest way to avoid digital noise is to use only ISO (less than ISO 400) and to maintain shutter speeds faster than 1 second.  This however, isn't always possible and as can be seen by the images above modern sensors have extremely good noise reduction built in.