TAOP - Light - Exercise Higher and Lower Sensitivity

Exercise-  Higher and Lower Sensitivity

The course notes are confusing here because the exercise talks about a first part but doesn't mention a second or subsequent part.

Anyway for the initial element of this exercise I have taken a series of images hand held of a single subject which in poor lighting conditions I have gradually increased the ISO until the shutter speed has increased to a reasonable level to reduce any potential camera shake that will be present when shooting hand held with a slow shutter speed (all images taken in aperture priority

All images in this initial set are at an aperture of f/3.2 for consistency

I've left the ISO at the base setting of 200. The camera has set a shutter speed of 1.6 seconds so being hand held the result image has camera movement

The ISO has been increased to 400 which has raised the shutter speed to 0.8 of second so again camera movement is seen in this image

The ISO has been increased to 800 which has raised the shutter speed to faster 0.4 of second. The image is getting sharper with the faster shutter speed (look at door mouldings). I'm not sure in this image I'm seeing any more noise than in the first image.  

The ISO is now at 1250 and the shutter speed slightly faster at 1/4 of a second

The ISO increased now to 1600 and the shutter speed increases to 1/5 of a second

The ISO increased now to 2000 and the shutter speed also increases now to 1/6 of a second


In this set of images I'm trading of increased ISO sensitivity to shutter speed. Once I reach a shutter speed of a round 1/4 to 1/5 of second I think the image is sufficiently sharp and further increases in ISO will not give me any more image sharpness / less camera movement. 

There is noise in these images but perhaps in testament to the camera's sensitivity abilities there appears minimal change in image noise. I think I'd be unlikely with the camera I'm using to start seeing dramatic noise increases until around 3200 to 6400


In this next set of images I've taken 3 pairs of images in challenging lighting conditions to judge movement at low ISO and then with increased ISO to eliminate movement

Pair 1

At ISO 200 the camera has set the fastest shutter speed it can in these lighting conditions to 0.8 second. At this slow speed the image has slight camera movement and most certainly subject movement

At ISO 1250 the shutter speed is now able to increase to a faster 1/5 second and the image shows no camera movement of subject movement. At this ISO I'm not seeing any increased noise at an ISO of 1250 with the image at 100%

Pair 2

I've deliberately selected a small aperture of f/18 which has resulted in a slow shutter speed of 1/13 second and there is some camera movement as it was handheld with ISO at 200

In this image using the same aperture just increasing the ISO to 500 has almost doubled the shutter speed to 1/25 allowing a more camera shake free image



Exercise Learning

a) In challenging lighting conditions, shooting in aperture priority, the resulting shutter speeds can be low and so both camera movement and subject movement can result - this can be unwanted

b) Increasing the camera sensor's light sensitivity by increasing ISO will allow faster shutter speeds and can help eliminate unwanted camera movement and subject movement

c) The trade-off to increasing ISO can be the inclusion of digital noise in an image. However in the majority of circumstances some noise is preferable to get a sharp image. Its far easier to reduce some image noise in post processing after the image has been taken than it is to increase an image's sharpness where camera movement and subject movement have occurred

d) Wedding photography in Churches where flash photography is not allowed would require higher ISO to obtain sharp images

e) From previous exercises I know increasing aperture size can increase shutter speed but this is will impact depth of field

f) It is important through either test experimentation or by research to understand at what ISO levels noise can start to impact an image and at what level noise becomes unacceptable. Understanding this will help the photographer judge to what ISO extremes he can go to in challenging lighting conditions and still get acceptable image quality