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Author Topic: 1Dx and CF card issue?  (Read 2436 times)

Kevin Weinstein

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1Dx and CF card issue?
« on: August 11, 2012, 11:40:41 PM »
So on my 1Ds MArk III with a 32 gig card, ISO at 800, I get 1037 images.

On my 1Dx using the same 32 gig card, ISO set at 800, I get 864.

Since my 1Ds Mark III has a higher pixel count, why is the 1Dx nearly 200 less images?

Both were reformatted when placed into the camera.

Thanks!

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1Dx and CF card issue?
« on: August 11, 2012, 11:40:41 PM »

neuroanatomist

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Re: 1Dx and CF card issue?
« Reply #1 on: August 12, 2012, 01:01:03 AM »
Do you mean actual shots recorded, or just what the camera estimates as shots remaining?

If you mean the latter, does changing the ISO matter?  It may be the camera just uses a standard average shot size to estimate, and since file size increases with increasing ISO, and the 1D X has a much broader range, it uses a larger average shot size.

If you mean the former, I'm stumped.

I haven't paid much attention to the counter, but when I was shooting a large series of AFMA shots (the only time I shoot JPG), I did notice that the counter incremented down only once every 2-3 shots, suggesting the camera was underestimating (rather severely) the number of shots remaining.
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weekendshooter

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Re: 1Dx and CF card issue?
« Reply #2 on: August 12, 2012, 02:43:16 AM »
+1 for the remaining shot estimate having the potential to be wildly off. I saw the same on my 450D and currently experience this on my (gasp) D700. It reads 605 shots remaining for an empty 16GB card, where I regularly get 1200+ in real conditions.

Just changing the ISO is not the whole story. File size is a function of the entropy of the image, which in this case is most commonly created through noise. As noise is typically highly amplified in shadow OOF regions, these are the sorts of images that will take up more card space. Images with high ISO shot in good light, such as for high shutter speeds, will not increase the file size as much as images shot in low light at high ISO with large amounts of dark OOF areas.

Viggo

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Re: 1Dx and CF card issue?
« Reply #3 on: August 12, 2012, 02:46:10 AM »
Is this in raw or jpeg? Do you have ALO enabled? Or lens correction? There are a lot of things that can increase file size.

Take the same shot with both and see if the file size is in fact the same.
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Kevin Weinstein

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Re: 1Dx and CF card issue?
« Reply #4 on: August 12, 2012, 07:24:14 AM »
Thanks everyone.

It is the latter situation.  Yes.

I shoot RAW, also.

I always found, on the 1Ds Mark III, that the number of shots (estimated) and number I get on a card to be pretty dang close.  Within 25.

Glad to know this is somewhat normal.

neuroanatomist

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Re: 1Dx and CF card issue?
« Reply #5 on: August 12, 2012, 09:42:32 AM »
As noise is typically highly amplified in shadow OOF regions, these are the sorts of images that will take up more card space. Images with high ISO shot in good light, such as for high shutter speeds, will not increase the file size as much as images shot in low light at high ISO with large amounts of dark OOF areas.

Not true.  Are you suggesting that the signal in dark areas of an image has a selectively higher gain, or something like that?  I don't buy that. Read and thermal noise are constant across the sensor. In brighter areas of the image, shot noise dominates and is added to the read/thermal noise, meaning there is actually more noise in bright areas. 

A quick empirical test demonstrates my point.  I set ISO 25600, f/10 in Av, shot one in-focus shot out the window (bright overcast) which metered at 1/6400 s, a second OOF shot inside a dark closet which metered at 0.3 s.  The outdoor shot size is 26.3 MB, the dark closet shot size is 30.3 MB - as the hypothesis predicts, the bright shot has more noise.

I think the explanation for your statement about more noise in dark, OOF areas is not technical, but psychophysical. The human visual processing areas try to form patterns, even where none exist (stare at a dense, regular, repeating geometrical feature and you can observe this).  In the bright and/or in focus areas, your mind pays attention to the subject(s), ignoring the noise.  In the dark OOF areas, there's nothing else to pay attention to, nothing to mask the noise, so you perceive it as amplified.

It is the latter situation.  Yes.

That's a relief, thanks for reporting back!
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Re: 1Dx and CF card issue?
« Reply #6 on: August 12, 2012, 01:53:20 PM »
+1 for the remaining shot estimate having the potential to be wildly off. I saw the same on my 450D and currently experience this on my (gasp) D700. It reads 605 shots remaining for an empty 16GB card, where I regularly get 1200+ in real conditions.

Just changing the ISO is not the whole story. File size is a function of the entropy of the image, which in this case is most commonly created through noise. As noise is typically highly amplified in shadow OOF regions, these are the sorts of images that will take up more card space. Images with high ISO shot in good light, such as for high shutter speeds, will not increase the file size as much as images shot in low light at high ISO with large amounts of dark OOF areas.
If the camera were amplifying the dark regions more than the light ones, all we would get is a gray image with little or no contrast.  Canon has not yet been able to control the gain of individual photosites, and, if they did, they still would not amplify dark ones to brighten them up.  Black is black.

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Re: 1Dx and CF card issue?
« Reply #6 on: August 12, 2012, 01:53:20 PM »