The objective of this exercise was to take similar shots at different ISO sensitivities and comparing the results, so I set myself up with a tripod by Derwent Water on an overcast day. I shot between ISO 100 and 3200, but cannot see any real differences in graininess, and due to the tripod, all shots were possible. I decided to repeat the experiment hand hold in a market place as the instructions recommend!
Second attempt shot in Borough Market taking advantage of the situation to try out my new prime lens (faster aperture so should perform better in darker conditions). My aperture was fixed at f/1.8 as I wanted to create blurred backgrounds and foregrounds and I allowed the shutter speed to adjust automatically I moved through the ISO settings.
ISO 100
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| 1/90s |
At ISO 100 the shot is perfectly clear. The exposure is aided by the lighting of the market stall. As the shutter speed at this ISO at aperture is fairly slow, I would think that with greater depth of field, the shot may not have been possible at ISO 100. A close up shows that there is no graininess in the photo but a narrower aperture would have given greater clarity in the shot.
ISO 200
The next image was taken outside the main market using a faster shutter speed. The smell coming from that stand was amazing! I could have used a more narrow aperture for this shot, but with the faster shutter speed there picture is quite clear.
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| 1/500s |
ISO 320
My camera is capable of ISO 250, but I wasn't expecting a huge difference, so my next shot was taken at ISO 320. Indoors again and back to slower shutter speed.
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| 1/90s |
An close up shows that a small amount of graininess is already creeping in. It's particularly visible on the block purple barrier sheets. This has surprised me - I wasn't expecting it to show at this ISO. So now I know! If I want to take an image that I intend to crop and enlarge, I need ISO 100 or 200.
ISO 400
Darker conditions, but a higher ISO affords a faster shutter speed: delicious paella!
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| 1/250s |
ISO 500
Continuing to move up through the ISO settings and although dark, I can use a fast shutter speed, or I could have narrowed the aperture.
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| 1/500s |
Examining the close up, there doesn't seem to be too much grain, although if I zoom in on the wooden branch, it's quite visible. So grain seems to be more obvious with flat colours.
ISO 640
A visit to the mushroom stand, conditions seem to be darker here, so depsite the higher ISO, a slower shutter speed is required. At this resolution, grain is still not visible.
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| 1/250s |
ISO 800
Delighted to find some Cumberland produce, and particularly Herdwick lamb, brighter conditions and a higher ISO afforded a faster shutter speed again.
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| 1/500s |
An enlarged extract shows that grain is ever presen, but it doesn't seem to be getting any worse.
ISO 1000
Now at the levels where I was personally expecting grain to start appearing. I think there would have been a good shot here if I'd taken more time - I liked the colours and tones in this image. Dull conditions, but the higher ISO is affording a faster shutter speed.
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| 1/750s |
The enlarged extract shows the grain quite clearly - particularly on the transparent counter casing.
ISO 1250
I've never ventured this far up the ISO settings so I was curious to see what the results would be. I couldn't resist this shot of the jacket that matched the hanging chilli peppers in both colour and the form of the quilting! It was quite dark in this outlet, so as expected, the shutter speed is lower.
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| 1/350s |
You still can't really see grain in a normal view, but the enlarged close up reveals that it is actually now getting worse!
ISO 1600
Back in the street - the longest queue of all the outlets was for the coffee shop. People need coffee more than food! This shot has quite difficult lighting to resolve - the daylight of the street, the darkness of the interior of the shop and the glow of the lamps. You can see that the people's faces are overexposed, and also not particularly clear. The camera set to a very fast shutter speed at this ISO, so if I was attempting this shot for real, I probably would have widened the aperture and perhaps tried the different metering options.
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| 1/1500s |
And as expected, the shot is grainy when cropped and enlarged.
ISO 2000
Again - difficult light to resolve and completely the wrong exposure for the conditions! Now on a very high shutter speed, but faces are still over exposed.
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| 1/3000s |
The close up is now very grainy!
ISO 2500
I like the depth of field (or lack of it) in this shot of the olive stand. Darker conditions, so a slower shutter speed than the shot above, despite the higher ISO, but still relatively fast. So if grain was not an issue, you could use the high ISO to get the clarity afforded by fast shutter speeds - or to give greater depth of field. I think grain here is starting to show at this resolution.
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| 1/1500s |
An enlarged extract now reveals quite a bit of noise - particularly in the blurred foreground.
ISO 3200
Last one of this series, although my camera does have higher settings still; some people enjoying a coffee. The shutter speed has decreased here - not sure why as the light was better than by the olive stand...Again the exposure isn't really working very well - there is too much reflection of the skin.
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| 1/1000s |
How is this useful?
Apart from knowing to keep the ISO as low as possible, to avoid noise, it could also be used the other way round to deliberately create noise. At the Wildlife Photographer of the Year exhibition one year, I remember seeing a shot of a grass plain with giraffe running across; it was shot in bright sunlight on a very high ISO to deliberately add grain, it was also deliberately blurred and produced in b&w. A very effective image.
I took this image at 1EV over 3200 (what does that mean??) - the grain is visible now at normal resolution.
And changed it to this! It resembles a photo taken by a private investigator!
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