- Daylight indoors (for the amount of light - outdoor sunlight would be too bright to allow high ISOs, while much darker would involve long exposure times)
- A combination of sharp detail and textureless areas (such as a white wall), with some of the textureless areas in shadow
Using the Aperture priority setting to ensure no changes to depth of field, I had to take a series of identical images changing just the ISO. The ISO range on my camera let me shoot from 100 to 6400.
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200
ISO 6400
Let's look at a close up crop of these.
ISO 100
Noise free
You might notice a little noise in the clothing but this is acceptable because of the texture and this is how we would expect it to look.
ISO 200
Still no sign of visible noise
ISO 400
Slight bit of noise visible but the blue edge of the iron is still in sharp focus.
ISO 800
Noise visible in the shadow area
ISO 1600
Again noise is visible in the shadow area and edge detail. Noise can be seen in the white area of the wall too.
ISO 3200
The shadow area is very noising and so is the iron. The edges of the blue rim affected too.
ISO 6400
This image is extremely noisy with speckles throughout the picture.
From this exercise I can see that using an ISO of over 800 introduces noticeable noise into your images. This is something to beware of. I rarely shoot with the ISO over 400 so this is something I've learned to avoid already in my work.
There are times though when you will be forced to shoot at high ISOs and the amount of noise in your images depends very much on the scene. Brighter scenes may have less noise whilst darker scenes with deep shadow areas will be greatly affected.
Of course, if you are converting the image to B&W you may not be put off by the noise especially if you are trying to achieve a vintage grainy look.
Tolerance for noise is not simply about the ISO it is also about the scene, processing and what you intend to do with your image.
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