File Sizes - High ISO = Larger Files?

[FlyingPete]

I have just been messing with ISO settings and NeatImage, making some comparisons between lower ISO images and higher ISO images corrected with NeatImage, and noticed something interesting.

When I took a sample shot of a scene at ISO 50, the file size was 1.47MB, when I took exactly the same shot at ISO 400 (same resolution compression settings etc), the image size was 2.20MB.

The only thing I can think of that would make the high ISO image larger is all the image noise being perceived as detail by the compression algorithm, therefore the high ISO image has more 'detail' in it.

Any thoughts?

[CyberDyneSystems]

Higher ISO images are indeed larger files. More color information and as you say, more noise! The Noise is image data!

On the 10D you can look at the "fuel guage" telling you how many images are left on your card,. as you increase the ISO the images remaining count drops... go from ISO 100 to ISO 1600 and the number of images will nearly be cut in half. (with jpeg files anyway,. the effect on the larger RAW file is a little less dramatic proportionally)

:)

[marcel wouters]

flyingpete wrote:
The only thing I can think of that would make the high ISO image larger is all the image noise being perceived as detail by the compression algorithm, therefore the high ISO image has more 'detail' in it.

Any thoughts?


This is what i call the "technocratic syndrome" or the "statistical virtual reality"!
Big size = more details!

Print your pic and see the result!
What result di you prefer?
This is the truth, other data is only irrelevant!

Auto generated details (artefacts) are not part of the original pic!
But of course increase the pic size!

Remember!
To sharp an image, first blur it then sharp it!
The blur remove inconsistency and the sharpen add edge contrast for good appearance!
This is why good camera didn't sharp too much!
Existing artefacts could not easily be removed!

[Jesper]

flyingpete wrote:
The only thing I can think of that would make the high ISO image larger is all the image noise being perceived as detail by the compression algorithm, therefore the high ISO image has more 'detail' in it.


That's right.... the compression algorithm can't know the difference between real image data and noise. The more smooth the signal is, the easier it is to compress; and the more random it is, the harder it is to compress.