Digital low noise test?

[hhelmbold]

Waiting for the 1D X I have had too many opportunities to shoot with different cameras as I rent a lot of bodies for different shoots. At the last wedding I did I mainly used available light as the venue was ideal and lighting was perfect for it, but I did have to push up the ISO a bit at stages. Something that I have taken for granted several times is that as soon as you push up the ISO, your number of available shots left on the memory card decreases, because noise takes "extra space" so to speak.

So I was wondering... The 7D and the 1D X are both 18 megapixel cameras and in THEORY if you take the same shot with both cameras the file size SHOULD be roughly the same... Am I correct?

But if the noise reduction is indeed lower on the 1D X, then we should see smaller file sizes compared to the 7D?

This is just something I was wondering about and would love to hear what others have to say about this?

[sanj]

Is the sensor size not of prime importance in this consideration?

[hhelmbold]

Is the sensor size not of prime importance in this consideration?

True... I was too focused on the megapixels and forgot about sensor size. But I would like to know what the file size comparisons are between FF 18 megapix and Crop 18 megapix.

But this is where the techno guru's can be of help :-) If I am not mistaken... Theoretically if you could set the camera's to take a 1024 x 768 photo at 18 megapix and take an identical photo with both cameras, the file size should be the same. BUT the fullframe captures a bit more of a dynamic range and thus more detail, so FF filesize will be more...

It was just a thought I had and I guess it is not really an easy comparison to make as there aren't same megapix cameras in "first and second generation" in terms of noise reduction. But I would love to see a filesize comparison between 5D mkii and mkiii of the same photo in RAW. The image processing algorythms will also be different between the cameras and this is just a very theoretical thought I had... but I thought it would be interesting to explore

[mb66energy]

Each compressed file format - if jpeg or RAW - lives from describing areas of identical pixel (color, brightness) with less data than describing EACH pixel itself. Example: If you have a lot of clean blue sky in your image, you find large areas with the same color&brightness. Compressing means that you describe these areas as a region of lets say 30x300 pixels with the SAME properties with some bytes instead of storing 30x300x3 bytes (the last 3 for the three primary colors).

If you use high ISO settings you will increase the noise. The mentioned area of 30x300 pixels hasn't the same color anymore but will be spoiled by noise. The compression algorithm doesn't see a region of SAME properties anymore and tries to find smaller areas with SAME properties or stores the pixels itself.

This effect can be seen just between different subjects: A blue sky with a few clouds doesn't need the same storage compared to a close up shot of very detailed scenes, I remember a shot of some objects in the sand. The sand grains force the compression algorithm to store pixel by pixel.

A larger sensor size with the same MP decreases the noise and ... the rise of storage demand with increasing ISO should be less observable.


Hopefully this explains the situation - best, Michael


Some remarks about compression:
RAW compression doesn't loose information. RAW just stores the data more intelligent just like ZIP-software which doesn't alter texts or other data (otherwise it wouldn't be very useful  ).
The JPEG compression deletes - depending on the degree of compression/quality - information.

[hhelmbold]

Each compressed file format - if jpeg or RAW - lives from describing areas of identical pixel (color, brightness) with less data than describing EACH pixel itself. Example: If you have a lot of clean blue sky in your image, you find large areas with the same color&brightness. Compressing means that you describe these areas as a region of lets say 30x300 pixels with the SAME properties with some bytes instead of storing 30x300x3 bytes (the last 3 for the three primary colors)...

Thanks for the explanation... I always knew how the compression works, but you put it more into perspective and it makes even more sense now. But it also highlights what I am trying to say. The new generation of 5 and 1 camera has better noise reduction. So even with keeping the compression algorythms in mind, if you take a picture with a 5Dmkii and take the same picture with the 5D mkiii  (if sensor sizes were the same) the newer 5D mkiii should give a smaller file size because there is less noise. The question is just... how much smaller... You should (once again in theory) get the same file size from the 5D mkiii at ISO 1600 that you would get from the 5D mkii at ISO 400 (if it is true 2 stops better noise performance and if sensors were the same size AND if it was the exact same picture)

A lot of IFs, ANDs and BUTs here 

[Drizzt321]

Each compressed file format - if jpeg or RAW - lives from describing areas of identical pixel (color, brightness) with less data than describing EACH pixel itself. Example: If you have a lot of clean blue sky in your image, you find large areas with the same color&brightness. Compressing means that you describe these areas as a region of lets say 30x300 pixels with the SAME properties with some bytes instead of storing 30x300x3 bytes (the last 3 for the three primary colors)...

Thanks for the explanation... I always knew how the compression works, but you put it more into perspective and it makes even more sense now. But it also highlights what I am trying to say. The new generation of 5 and 1 camera has better noise reduction. So even with keeping the compression algorythms in mind, if you take a picture with a 5Dmkii and take the same picture with the 5D mkiii  (if sensor sizes were the same) the newer 5D mkiii should give a smaller file size because there is less noise. The question is just... how much smaller... You should (once again in theory) get the same file size from the 5D mkiii at ISO 1600 that you would get from the 5D mkii at ISO 400 (if it is true 2 stops better noise performance and if sensors were the same size AND if it was the exact same picture)

A lot of IFs, ANDs and BUTs here 

Not necessarily, because while you might have less noise, you might have more detail. So if you're looking at, say, and very detailed piece of sculpture or something, the filesize difference between high ISO w/low lighting might give you about the same file size as at low ISO w/good lighting.

Not really sure what this has to do with digital noise testing though...

[hhelmbold]

Not necessarily, because while you might have less noise, you might have more detail. So if you're looking at, say, and very detailed piece of sculpture or something, the filesize difference between high ISO w/low lighting might give you about the same file size as at low ISO w/good lighting.

Not really sure what this has to do with digital noise testing though...

I think we are saying the same thing here about FF and non FF sensors and that one records more detail than the other. But I am saying file size could be a digital way in testing (actually comparing I suppose) low noise instead of looking with the eyes. IF you had a 1st generation FF sensor at 18 megapix and a FF 2nd generation sensor at 18 megapix, the 2nd generation low noise camera should give smaller file sizes if it really records 2 stops less noise.

But the reality is that we don't have 2 such cameras to test with - so this stays a theory