Thursday, 25 August 2011

Exercise - Higher and Lower Sensitivity

This exercise is to look at different ISO settings and how they effect image taking. A higher ISO equates to a higher sensitivity to light, which should make taking a handheld picture easier - but there is a payoff  in increased noise - which may make the picture unpleasant to look at.

Example 1.

ISO 100, f/5, 90mm efl, 1/10 sec.

This picture was handheld at the limits of my ability, it is not quite pin-sharp, although this hardly shows given the 'soft' look of the elephants covering.

ISO 400, f/7.1, 90 mm efl, 1/25

Increasing the ISO to 400 has meant the picture is sharper as it was taken at 1/25 sec, there is also a slightly greater depth of field.There is little increase in noise even when looked at at 100%.

 Example 2.

ISO 100, f/5.5, 70 mmefl, 1/10 sec

Here the picture is almost sharp (has not been sharpened digitally) and has a very low key effect, with little detail visible in the background.

ISO 400, f/5.5, 70 mmefl, 1/10 sec.

In this image the ISO has been increased to 400, while all the other settings have remained the same, the picture is much brighter, with more detail in the undergrowth, bur less mysterious, and I think less pleasing. The background areas do show some noise at 100%, with a degree of speckling.

Example 3.

ISO 125, f/2.5, 44 mm efl, 1/80 sec.

Here the low ISO was compensated for by a wide aperture, giving a very short depth of field, which did not include the candle and the glass (only the glass is sharp).

ISO 400, f/8, 44 mm efl, 1/25 sec

This time the higher ISO has allowed a lower aperture (helped by also a longer shutter speed) and the whole of the image is in focus. This would benefit from being cropped and lightened and possibly converted to monochrome.

Example 4.

ISO 100, f/3.3, 106 mm efl, 1/5 sec.

This picture of flowers at the wedding, was a failure at ISO 100 as the shutter speed was too slow and it is out of focus.

ISO 400, f/3.3,  106 mm efl, 1/20 sec

Increased ISO has allowed the shutter speed to be dropped enough to keep the flowers sharp. The already grainy background of the stones hides any noise from this increase.

Example 5.

ISO 100, f/2, 28 mm efl, 1/8 sec.

In the image everything is slightly out of focus. I was aiming to get the backs of the heads sharp, showing people waiting for the wedding to begin. Flash was not possible because of the distances invovled and the setting.

ISO 400, f/2, 28 mm efl, 1/25 sec.

This time the shutter speed was fast enough to show the effect I was after, concentrating on showing the people waiting. Unfortunately the actual image is less good as people have moved and the girl with a red jacket is not so visible!

Example 6.

ISO 100, f/2.9, 65 mm efl, 1/15 sec.

This image is much to dark. It could be lightened digitally. However to do this enough to see the detail in the dancer the contrast is altered and some image artifact occurs, with the colour looking unnatural.

ISO 400, f/2.9, 65 mm efl, 1/10 sec.

Here the statue is much lighter and the detail is visible, while the colour is maintained. Flash would have been possible but would have reflected off the shiny surfaces. There is slight noise visible in the black areas, but it is still more successful than over lightening the previous image. (using a tripod and a slower shutter speed would have been better still).

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