Prior to undertaking this exercise, I thought I should undertake a little research> ISO settings are now part of every day digital photography. But this has not always been the case as in the days of wet film.
Bryan Peterson in Understanding Exposure-ISBN 081746300-3, pages 20-26) explains why ISO settings are so important. He, as always, make was could be a rather complicated subject a little easer to understand by using worker bees. (1 iso =1 worker bee)
” …. If my camera is set to iso 100 and yours to iso 200 you have twice as many bees than me. So if the two cameras are set to the same settings your camera will need less time to capture the same image as me image as there are twice as many bees bringing light to your camera.”
“… when you increase the iso (or number of worker bees) you cut the time necessary to get the image captured…”
Iso settings are part of the Photographic triangle which is made up of the following
- Iso Setting
- Shutter Speed
And the second
Here are two screen shots at 100%
Screen Shot above
There is a clear difference between the two screen shots, especially the sky.
I took a further image of the skyline as it got darker to see if the results would be the same. Although this image was effected by the wind causing movement to the camera , as you see.
Later I walked along Victoria Street to see if I could capture an image at an even higher iso.
I found girl camped out , waiting for the Royal Wedding. She had picked a dark spot under some trees, so she could get some sleep.
I decided that if I were a press photographer I would need to get this sort of image what ever the situation. I worked my way through the iso setting untill I got this image.
I found that in order to get an image that was of any use I had to go up to Iso 5000. The screen shot below shows what the image would be like at 100% crop.
I chose an area in the image that contained writing to show a greater effect.
You can clearly see noise and although you can not read the writing the images are still visible.
Further images were now required to see how high I could push the camera and still have a usable image. I captured this image of a cameraman
It was very dark here , but I got an image that was reasonably clear, however as you will see from the screen shot a lot of noise is shown. As a further test I decided to take this crop at 150%. The results were interesting as you can see.
The audio ports can be seen and the writing is still visible.
I noted that the noise appears to be more visible on the black parts on the image rather than the silver. I noted similar results on some of the crops above.
Is noise greater on dark sections of the image or lighter sections?
In view of the above results I set off again to try and find an image that would test the camera even further.
Again this shot was taken hand-held in the street.
After looking at the result we are now getting to the stage where the quality of the original image is showing a lot of noise. I think that this is still a usable image if it was captured by a press photographer of an important event that nobody else had captured.
Below are two crops, one at 100% and a second t 150%
and the second
These crops were taken from this area of the original image
The 100% crop still shows detail however the 150% crop is, in my view, of little use.
I decided to go back onto the roof of the building I was using to get a further long distance image of a London landmark from a distance. There would be very little light , due to the distance , so my only option would be to shoot using very high iso.
Here is the result, I’m sure we all know this building.
Here is the crop at 100% , which I was rather pleased with
Clearly lots of noise, but there is still detail, look at the brick work and the detail in the tower behind.
How would conversion to black and white effect the image if it was say, going into a newspaper, well her is the result.
I thought that this looked better, what do you think?
End of great exercise.Further review to follow.