Saturday, 8 January 2011

Exercise 29 - Higher and Lower Sensitivity

 The weather prevented my from capturing the suggested street scene for this exercise so I decided to use a poorly lit room and have the cats playing with a toy so that there was some movement. using me wide angle lens at its widest aperture the average exposure reading was 0.6 secs when using ISO100. My camera does have ISO 50 but I read that this is a digital simulation and not the best the sensor can do so I never use it. 

 So as the ISO is increased I am able to use a faster shutter speed and reduce the amount of blur caused by the movement of the cats. The difference between the shutter speed is small at first and a tripod was used for all of these shots which obviously helps maintain the composition but also allows for slow shutters and a better ISO demonstration.

By the time I got up to ISO 800 the shots reasonably exposed with little blur. The lens I was using doesnt have any kind of image stabilisation but I must also acknowledge the fact that as time went on the cats got less interested in their race track thingy and were moving about less.

The jump up to 6400, the highest setting allowed a shutter speed of 1/80 which effectively froze the action. I could at this point have achieved it hand held but the image shows how the quality has degraded as a result.

Shadow Close-ups

Here you can see that with the ISO ramped up to 32 the detail in the shadow (on the darker cat) is lost to the point where it is just specs of light and dark.
The same cat in shadow at ISO 100 is smother with a lot more fine detail, albeit lost in blur due to the necessary slower shutter speed.

The lighter areas which are smooth with little detail show the noise much more clearly. At ISO 3200 the wall is a mess of noise and artefacts.

At ISO 100 the wall is smooth and clear.

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