Friday, 7 January 2011

Exercise: Higher & lower Sensitivity

In this exercise we are to explore the effects of ISO levels against the amount of light that they require and any side effects. It is clear that higher ISO (or faster films) require less light and produce faster shutter speeds. However the cost of this additional speed is quality, just as with fast film that is more grainy, digital sensors too suffer from noise. The following images show this in detail. 
The first image taking in a subway is IOS 100 and given the available light even at f2.8 only produces a shutter speed of 1/6 showing motion blur in the people.



Raising the ISO level to 800 gives a respectable speed of 1/90 second in which I have a clear and sharp image.


Looking at the walls which are a neutral part of the images at 100%, it is clear that the amount of digital noise has increased and the second image at IS0 800 is much more grainier.




In concentrating on a darker part of the image it can be seen that there is more digital noise (speckles) in the second image, though I think the camera has done quite a good job here at reducing this and there is a good level of detail



The following 6 images also follow a similar pattern, the first shows motion blur at ISO 100 and 1/10 of a second but a good clean image, whilst the second at the higher end of ISO 1250 has a crisp image at 1/125 of a second.



However on investigation at 100% the floor can be seen to be significantly nosier using the higher ISO setting of 1250.



Finally , in the darker parts of the images it can clearly be seen that there is a lot more speckled digital noise in the high ISO image. The image at 100 is blurred but certainly no noise at all.



In conclusion using higher ISO values is a useful tool when shooting in low light where faster shutter speeds are required, but only as a last resort and always switch back to the standard 100 ISO once finished.

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