Exercise: Higher and Lower Sensitivity.

For this exercise take similar shots at normal and high sensitivity. Note whether there were photographs that could not be taken successfully at the lower sensitivity but were possible at the higher sensitivity. Compare the two images close up, what are the obvious differences and note the outcome.

1.

1/200 f7.1 ISO 200 48mm

2.

1/200 f14 ISO 800 48mm

Once I had enlarged the digital view to 100% there was not as great a difference between the too images as I was expecting. I looked in two places, the first in the middle of the paddock where there is less detail and the second at the base of the tree where there are deeper shadows. The ISO at 800 does obviously show some noise but for some reason I think I was expecting it to be greater.

3.

1/800 f5.6 ISO 200 90mm

4.

1/3200 f5.6 ISO 800 90mm

For a start I am unsure why the shutter speed was so fast for this shot, I'm not really sure what I was thinking but it is rather unnecessary. The difference between these two shots is instantly noticeable. The grainy effect of the higher ISO can be noticed before I even blew it up. Set to 100% the ISO 200 image still retains clarity in the centre of the frame where as the image with  the higher ISO has lost that detail.

5.

1.400 f3.5 ISO 200 18mm

6.

1/1600 f3.5 ISO 800 18mm

Whilst photo 6 does show quite a lot of noise, although not as much as I was expecting again, I actually quite like the speckled quality that this gives the image more so than photo 5.

7.

1/50 f4.8 ISO 200 42mm

8.

1/200 f4.8 ISO 800 42mm

After blowing these images up there is obviously quite a lot of graininess to photo 8. There is no real area that is smooth with little detail so this was not an option for comparison. There are areas of deeper shadow which again have quite a lot of the speckled appearance. Even blowing up the image slightly shows considerable noise.

9.

1/80 f4 ISO 200 28mm

10.

1/400 f4 ISO 800 28mm

Here I have gone for another quite detailed image with varying tones. I was actually expecting the image with the higher ISO to have considerably more noise in it that it actually does. The grainy quality it still there but in this image it does not bother me too much. Obviously if this image was to be say A4 or larger then I would not be as happy, but wallet sized the noise is hardly noticed.

11.

1/60 f5 ISO 200 58mm

12.

1/250 f5 ISO 800 58mm

There is not really a large difference between the two here.

Conclusion.

Overall the higher the level of sensitivity the more the image will show a more grainy, speckled quality. The noise is caused by there being a less than ideal quantity of light reaching the sensor. In some images I have found that while the level of noise present may be quite high, it has not actually bothered me too much and I quite like the grainy appearance. This is obviously less than ideal in many circumstances and does also depend on the size of print being created. The larger the print will be the more the noise will be noticeable. I also think that if the subject being photograph is particularly interesting then the noise may be less noticeable.