The Holding Tank

Hardware

EOS 7D vs 20D ISO Performance

| Noise Crops No NR |

| Noise Crops Default NR |

Table of Content

Introduction

No Noise Reduction Results

Default Noise Reduction Results

Conclusions

Introduction

This test looks at the 7D noise performance over its ISO range comparing this to my previous camera the 20D. Currently the only RAW converter I have in common is DPP 1.7 supplied with the 7D, so all the results are produced by this converter.

For a meaningful comparison it is necessary to compare noise and sharpness and try and keep one parameter nearly equivalent. This test is designed to check both.

The test target was exposed using an exposure setting derived from an incident light meter. No contrast, white or black point adjustments have been made in DPP even though this is a low contrast subject. Clearly in normal photography one would attempt to expose to the right as much as possible. The 7D files had the "Standard" picture style set.

The EF 100mm f2.8 macro USM lens at f8 was used in all cases. All 7D exposures have the same focus setting as do all the 20D exposures.

Two sets of results are produced, No Noise Reduction where the sliders for luminance and chrominance noise reduction and DPP sharpening are set to zero.

The second set Default Noise Reduction, uses the DPP default luminance and chrominance noise reduction settings but still sets the DPP sharpening to zero.

The DPP defaults and settings used are tabulated here.

The post processing sequence is defined below:

a) Conversion to 16 bit TIFF using DPP 1.7.

b) Sharpening using my standard lens test process Photoshop Action, that is also used to check the MTF 50% sharpness in these noise tests, see here. This is minimal sharpening sufficient to just overcome the camera anti-alias filter. It is edge masked and so will not affect the noise levels of flat areas of tone used for noise measurements. The output of this process are 8bit TIFFs in sRGB.

[Note that the MRAW and SRAW sizes will not be band limited by a physical filter; however assuming Canon are doing the down sample correctly, rather than just binning, some software lowpass filter will need compensating for.]

c) The 20D RAW, 7D RAW and 7D MRAW are then also down sampled to the 7D SRAW size (2592 X 1728) using the Photoshop "bicubic sharper" algorithm. This provides a common resolution size for comparison that is close to a minimal print resolution (230 dpi on A4).

The MTF 50% sharpness was then measured using ISO slanted line method software as detailed above. Additional the RMS noise level of the black test tone was recorded using bespoke software. The two software packages also produce crops of the areas measured. The crops can be accessed using the menu system above.

A note about the measured MTF 50% sharpness. In earlier lens tests the 100mm macro on the 20D achieved a sharpness of about 66 lp/mm in the centre at f8 using the Adobe Camera RAW processor and same sharpening method.

These test are clearly not 100% perfectly focussed as the ACR result at 100 ISO on the 20D is only 58 lp/mm, however this is still a very good level of sharpness and will be sufficient for evaluating the effect of noise and its reduction on the sharpness.

Additional when converted using DPP the same frame gives about 50 lp/mm, clearly the DPP demosaic algorithm includes less gradient emphasis than ACR.

The 7D RAW at 100 ISO managed about 56 lp/mm via DPP. I am fairly sure better performance is possible, but again this is more than enough for the test.

For information the SRF plots for the two camera's full resolution without and with noise reduction are shown here.

Below, you will find the principle parametric plots for the two test groups. Finally the conclusions section will discuss the results and draw the conclusions of the test.

No Noise Reduction Results

Default Noise Reduction Results

Conclusions

No Noise Reduction Results.

Although this gives the sharpest results the noise performance of the 20D and 7D is essentially the same over their common ISO ranges.

Downsizing by using MRAW or SRAW or by using the bicubic sharper algorithm on the RAWs reduces the noise levels a little. These trends are fairly clear for the luminance noise, but less so for the chrominance, however the chrominance noise is fairly well clustered.

For the RAWs the sharpness degrades towards the higher ISOs as might be expected. Using smaller RAW formats or downsampling compresses together the resolution traces and reduces the effect of the high ISO, again as might be expected.

Default Noise Reduction Results

Using the default DPP noise reduction settings reduces the 7D files sharpness slightly, but has a dramatic detrimental effect on the 20D file MTF 50% sharpness that is apparent even after downsampling.

Despite this, the reduction in 7D luminance and chrominance noise is very significant compared to the 20D [The default DPP settings for the 20D do not include any chrominance NR!!]. The luminance advantage is about two stops and the chrominance advantage is about 3 stops at the maximum ISO settings.

Again, downsampling or lower resolution RAWs reduces noise levels, sometimes not by much, although for the SRAW this reduction is more significant.

Noise Performance at Comparable Sharpness Levels

The sharpness of the 20D RAW image is comparable or slightly lower than the 7D RAW image when the 20D has no noise reduction and the 7D has the default noise reduction.

On this basis, at 3200 ISO, the luminance RMS noise on the 7D is about 3 and the 20D is about 8. For the same sort of noise level the 20D would need to be around 400-800 ISO, so a 2-3 stop advantage.

Similarly, for the chrominance noise at 3200 ISO the 7D achieves an RMS noise level of about 1.5 and the 20D about 5.5. To achieve 1.5 the 20D would need to be at 100 ISO and is still not quite as good, so a difference of 5 stops or more.

In Summary

Using no noise reduction will not in general be optimal for the 7D, dramatic improvements in noise performance are possible with a little noise reduction without compromising sharpness excessively.

However, when operating at 100-200 ISO, with ideal to the right exposures, it may be desirable to maximize sharpness by minimizing noise reduction.

At high ISO some noise reduction is very advisable for the 7D. For comparable or better sharpness the 7D is capable of a noise performance that is 2-3 stops better than the 20D.

Last Updated 17/10/2009

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