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Author Topic: 5D Make II ISO characteristics  (Read 4746 times)

Panopeeper

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5D Make II ISO characteristics
« on: October 26, 2008, 11:47:56 pm »

I downloaded the raw files from the akihabaranews site and made some preliminary analysis. Preliminary not because the camera is a preproduction copy (it is naive to believe, that the sensor will be changed of a camera, which hits the shops in two-three weeks). Preliminary, because the shots are only limitedly suitable for such objective analysis.

I measured the per pixel noise in terms of standard deviation on selected spots in a selected raw channel. It is important to understand, that it plays no role, which channel is picked, only the pixel values are of meaning in this aspect.

The first observations are:

- the top real ISO is 3200; compare this to  5d: 1600, Nikon D3: 6400, 1DMkIII; 6400, 1DsMkIII: 3200, 40D: 1600, 50D: 3200;

- the 1/3 EV ISOs are fake, like with the 40D and 50D, unlike the Nikon D3, the Canon 1DMkIII (and probably the 1DsMkIII). Though this is irrelevant for raw shpooters;

- the per pixel noise is practically equal to the 5D at ISO 400 and slightly lower than the 5D at ISO 1600;

- compared to the Nikon D3: they are so close, that the results of measurements are somewhat ambiguous.

Some scepsis about the real usefulness of higher ISO gain is justified. Sensor manufacturers can increase the gain until it "catches" a single electron, but does the gain contribute to the image content with details (better distinction between details with almost identical intensity), or will only the noise be increased?

My first observations based on these 5D2 raw files are that

1. the step from ISO 800 to 1600 yields a big real gain,

2. the step from ISO 1600 to 3200 is almost worthless.

(As posted already earlier, ISO 6400 does not yield any real gain).

To 1: I don't have any ISO 800 shot, but I do one with ISO 640, which is the same as ISO 800; however, it has been shot not 1 EV but 1 1/3 EV higher than the ISO 1600 shot (of course), thus the DRP adjustment has to be 1.33.

Example:

5D2 ISO 640 DRP 8.31 NR 26

A spot with the same amount of captured light appears in the dynamic range position 1.33 EV higher in the ISO 1600 shot.

Example: ISO 1600, DRP 7.01, NR 20; *the ISO gain reduced the noise a lot*:

5D2 ISO 1600_DRP 7.01NR 20

To 2:

a) Both shots were made @ f/6.3, the ISO 3200 with 1/20s, the 1600 with 1/10s, The histograms show, that these shots are directly comparable:

5D2 ISO 1600 Histogram
5D2 ISO 3200 Histogram

b) The noise-to-signal ratio (NR) in the ISO 1600 shot at the dynamic range position (DRP) 7 is about 20%; I found this in several selections, one example is posted just above.

c) Pixels with the same amount of captured light appear in the ISO 3200 shot 1 EV intensiver ("brighter"), i.e. at DRP 6. Several selections show, that the NR is 19%, i.e. the one stop higher ISO managed to reduce the noise to signal ratio from that fixed amount of light only 5%; *this is meager*. One example for such a selection (keep in eye: the color is irrelevant; the subject is not the light coming through the lens but the light captured by the sensel);

5D2 ISO 3200 DRP 6 NR 19

d) Only for comparison: the NR in a shot with ISO 3200 at DRP 7 (i.e. half the light compared to the selection with DRP 6) is 32%:

5D2 ISO 3200 DRP 7 NR 32

The analysis has been done by Rawnalyze
« Last Edit: April 26, 2009, 09:04:49 pm by Panopeeper »
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Gabor

BruceHouston

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5D Make II ISO characteristics
« Reply #1 on: October 27, 2008, 04:50:07 am »

Quote from: Panopeeper
I downloaded the raw files from the akihabaranews site and made some preliminary analysis. Preliminary not because the camera is a preproduction copy (it is naive to believe, that the sensor will be changed of a camera, which hits the shops in two-three weeks). Preliminary, because the shots are only limitedly suitable for such objective analysis.

I measured the per pixel noise in terms of standard deviation on selected spots in a selected raw channel. It is important to understand, that it plays no role, which channel is picked, only the pixel values are of meaning in this aspect.

The first observations are:

- the top real ISO is 3200; compare this to  5d: 1600, Nikon D3: 6400, 1DMkIII; 6400, 1DsMkIII: 3200, 40D: 1600, 50D: 3200;

- the 1/3 EV ISOs are fake, like with the 40D and 50D, unlike the Nikon D3, the Canon 1DMkIII (and probably the 1DsMkIII). Though this is irrelevant for raw shpooters;

- the per pixel noise is practically equal to the 5D at ISO 400 and slightly lower than the 5D at ISO 1600;

- compared to the Nikon D3: they are so close, that the results of measurements are somewhat ambiguous.

Caveat: I am suspecting, that these shots have been made with High ISO Noise Reduction and that it has affected the raw data. If so, the noise measurement is invalid; but it is possible, that only ISO 6400 and above are affected.

Some scepsis about the real usefulness of higher ISO gain is justified. Sensor manufacturers can increase the gain until it "catches" a single electron, but does the gain contribute to the image content with details (better distinction between details with almost identical intensity), or will only the noise be increased?

My first observations based on these 5D2 raw files are that

1. the step from ISO 800 to 1600 yields a big real gain,

2. the step from ISO 1600 to 3200 is almost worthless.

(As posted already earlier, ISO 6400 does not yield any real gain).

To 1: I don't have any ISO 800 shot, but I do one with ISO 640, which is the same as ISO 800; however, it has been shot not 1 EV but 1 1/3 EV higher than the ISO 1600 shot (of course), thus the DRP adjustment has to be 1.33.

Example:

5D2 ISO 640 DRP 8.31 NR 26

A spot with the same amount of captured light appears in the dynamic range position 1.33 EV higher in the ISO 1600 shot.

Example: ISO 1600, DRP 7.01, NR 20; *the ISO gain reduced the noise a lot*:

5D2 ISO 1600_DRP 7.01NR 20

To 2:

a) Both shots were made @ f/6.3, the ISO 3200 with 1/20s, the 1600 with 1/10s, The histograms show, that these shots are directly comparable:

5D2 ISO 1600 Histogram
5D2 ISO 3200 Histogram

 The noise-to-signal ratio (NR) in the ISO 1600 shot at the dynamic range position (DRP) 7 is about 20%; I found this in several selections, one example is posted just above.

c) Pixels with the same amount of captured light appear in the ISO 3200 shot 1 EV intensiver ("brighter"), i.e. at DRP 6. Several selections show, that the NR is 19%, i.e. the one stop higher ISO managed to reduce the noise to signal ratio from that fixed amount of light only 5%; *this is meager*. One example for such a selection (keep in eye: the color is irrelevant; the subject is not the light coming through the lens but the light captured by the sensel);

5D2 ISO 3200 DRP 6 NR 19

d) Only for comparison: the NR in a shot with ISO 3200 at DRP 7 (i.e. half the light compared to the selection with DRP 6) is 32%:

5D2 ISO 3200 DRP 7 NR 32

The analysis has been done by Rawnalyze

Thanks for putting the work into this, Pano; very helpful!

Bruce
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Ray

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5D Make II ISO characteristics
« Reply #2 on: October 27, 2008, 05:37:16 am »

Gabor,
You seem to have put a lot of work into that analysis, but some of the the source images may be suspect, as you mention, which is a pity.

What I find with the 5D is that image resolution begins to decline above ISO 400, however slightly. But at ISO 1600 it's noticeable. If I were to upgrade to the 5D2, I would hope that at ISO 3200 (with the 5D2) I could get a large print as sharp and at least of equal quality in all respects to a 5D shot at ISO 1600, assuming an ETTR for both images. That is, at least equal resolution, at least equal DR and at least equally low shadow noise, for an equal size print.

Would you estimate that this would be the case?
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Panopeeper

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5D Make II ISO characteristics
« Reply #3 on: October 27, 2008, 09:18:02 pm »

Quote from: Ray
What I find with the 5D is that image resolution begins to decline above ISO 400, however slightly

I don't understand the correlation. I am really interested to see images demonstrating this effect, if possible then somehow objectively.

Quote
If I were to upgrade to the 5D2, I would hope that at ISO 3200 (with the 5D2) I could get a large print as sharp and at least of equal quality in all respects to a 5D shot at ISO 1600, assuming an ETTR for both images. That is, at least equal resolution, at least equal DR and at least equally low shadow noise, for an equal size print.

Would you estimate that this would be the case?

I can't even speculate on this, and If I could, I would not publish it, for I myself dislike speculations. Particularly the resizing issue is suspect for me, I am not into equalizing totally different images.

Anyway, it seems that the three years difference in the technology made it's mark.

If you posted shots of Jonathan's DR sheet (STRONGLY underexposed, at least 3 EV) or a Stouffer wedge or an underexposed color checker with different ISOs, I would make more comparisons. I have such shots from you, very suitable for making measurement, but they are all ISO 100.
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Gabor

Ray

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5D Make II ISO characteristics
« Reply #4 on: October 27, 2008, 10:25:41 pm »

Quote from: Panopeeper
I don't understand the correlation. I am really interested to see images demonstrating this effect, if possible then somehow objectively.

I must admit, I haven't done any objective testing of this issue. It's just an impression I get from shooting a variety of scenes over the years. The effect can be seen at Imaging Resource's comparator, comparing A900 shots with 1Ds3 shots of the same target at various ISOs. At base ISO of 200, the A900 is at least the equal of the 1Ds3, perhaps providing marginally greater detail than the 1Ds3, but matters change rapidly above base ISO for the A900. By ISO 1600, the 1Ds3 is shown as producing noticeably better detail than the A900.

 
Quote
If you posted shots of Jonathan's DR sheet (STRONGLY underexposed, at least 3 EV) or a Stouffer wedge or an underexposed color checker with different ISOs, I would make more comparisons. I have such shots from you, very suitable for making measurement, but they are all ISO 100.

I'll try to do this when I have the time. Perhaps I'll also use a Norman Koren line chart.
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Ray

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5D Make II ISO characteristics
« Reply #5 on: October 27, 2008, 11:05:20 pm »

Quote from: Panopeeper
Particularly the resizing issue is suspect for me, I am not into equalizing totally different images.

I have difficulty in understanding your objection here. If one uses, for example, an A3+ printer which produces a maximum print size of 13"x19", then one would quite likely make A3+ prints whether one's camera is an old-fashioned Canon D60, a modern 50D or a G10. Both the 50D and G10 will make A3+ size prints at 240ppi without upsizing. The D60 image would have to be interpolated to get an A3+ print at 240ppi. On the other hand, if one's printer is an A4, or if A4 size is roughly as big as you want to print, say 8"x12", then the D60 images will be fine at native resolution and 240ppi, but the 50D and G10 images would need to be downsized.

In practice, it would probably be better to raise the ppi in proportion to the downsizing so that no information is thrown away. At least, that's what I do, although one would be hard pressed to see any difference between 240ppi and 360ppi (or 400ppi) on the print, without using a loupe.
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Panopeeper

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5D Make II ISO characteristics
« Reply #6 on: October 28, 2008, 12:09:22 am »

Quote from: Ray
I'll try to do this when I have the time. Perhaps I'll also use a Norman Koren line chart.

But please think of smooth, unicolored, very evenly illuminated spots in the very deep shadows for measuring the noise.

Quote
I have difficulty in understanding your objection here. If one uses, for example, an A3+ printer which produces a maximum print size of 13"x19", then one would quite likely make A3+ prints whether one's camera is an old-fashioned Canon D60, a modern 50D or a G10

If a shot does not satisfy my quality requirement, then I don't qualify it as "good, but small".
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Gabor

Ray

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5D Make II ISO characteristics
« Reply #7 on: October 28, 2008, 08:24:59 pm »

Quote from: Panopeeper
If a shot does not satisfy my quality requirement, then I don't qualify it as "good, but small".

I still don't understand. Are you equating pixel count with technical quality? My experience is, that the technical quality of a shot will depend on factors such as, good exposure, sufficiently fast shutter speed for the conditions, correct choice of aperture for desired DoF, use of a good lens which doesn't produce soft edges, blurred corners or unwanted flare, and accurate focussing.

I make prints of a variety of sizes depending on the nature of the subject rather than the pixel count of the camera. I have produced 24"x36" prints from 6mp D60 files, which I think look just great.

Noise and general loss of image quality at high ISO I have always found to be a problem. I have quite a few shots, taken on the spur of the moment with camera in aperture priority mode, which are good only for small prints because the shutter speed was inadequate. I don't know why Canon have not given us a programmable auto-ISO feature, like some Nikon models. That is, set the desired aperture and shutter speed and let the camera choose the appropriate ISO.

I've also taken images which are not sharp as a result of indecision about the trade-off that can take place when one moves up to a higher ISO for the sake of a faster shutter speed. Which is better, a tack sharp image obscured by noise, or a less sharp image with less noise?
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marcmccalmont

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5D Make II ISO characteristics
« Reply #8 on: October 29, 2008, 01:01:28 pm »

Any analysis of DR?
Marc
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Marc McCalmont
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