Please note that the camera comparisons are only based on image quality. Also note that all images are down-sampled to the size of the sensor with the lowest resolution (12 MP, Nikon D3s).
Compared to Canon 5D Mark II
Let’s see how much better the new 5D Mark III is compared to the older 5D Mark II.
Canon 5D Mark III vs Canon 5D Mark II ISO Comparison at Low ISOs
Here are some low ISO image comparisons between ISO 100 and 800 (Left: Canon 5D Mark III, Right: Canon 5D Mark II):
It is hard to see much difference between the two cameras at low ISO levels – both perform really well from ISO 100 to 400.
At ISO 800, the Canon 5D Mark II seems to have a little more noticeable noise, but it is still quite good in comparison.
Canon 5D Mark III vs Canon 5D Mark II High ISO Comparison
The situation starts to change when ISO levels are increased on both cameras:
You can see a little more noise on the 5D Mark II throughout the image, especially in the shadows.
ISO 3200 still looks worse on the 5D Mark II.
And ISO 6400 is noticeably worse on the 5D Mark II, especially in the shadow areas – noise is more pronounced and grain is clearly bigger in size. I did not bother providing boosted ISO levels on the 5D Mark II, because they look very similar to the above ISO 6400 crop, with the 5D Mark II having more noise with higher color and detail loss.
Canon 5D Mark III vs Canon 5D Mark II Summary
At low ISO levels from 100 to 400, both DSLRs look very similar with no noticeable noise. At about ISO 800 though, the Canon 5D Mark III takes the lead, providing cleaner images with more details and colors. The difference in sensors is clearly seen at ISO 6400, where the 5D Mark II seems to be about 2/3 of a stop worse in comparison. The biggest advantage of the new 5D Mark III sensor seems to be at high ISO levels, where it seems to apply a more clever noise reduction algorithm, similar to what Nikon did when going from D3 to D3s.
Also, the resolution of the 5D Mark III is a little higher in comparison, so the size of pixels got a little smaller, while noise performance has gotten better. Had the number of pixels stayed the same, we would have seen even better performance, but Canon probably did not want to look like it did nothing to the physical sensor. Is there are a two-stop difference between the Canon 5D Mark III and 5D Mark II like Canon has been claiming? No, absolutely not. Simply because the new 5D Mark III has two more native ISO levels to use does not mean that it is in fact two stops better.
See the above crops for yourself – do you see a two-stop difference at any ISO level? If there was a two-stop difference, ISO 6400 on the 5D Mark III would have looked about the same as ISO 1600 on the 5D Mark II – it clearly does not. Sadly, the 2 stop improvement claim is just a myth – it is a clever marketing trick that all manufacturers are sadly using today to make people believe that an upgrade is justified. The 3-year-old sensor on the 5D Mark II still yields beautiful images that are only marginally worse, and only at high ISOs.
Please note that all of the above images were compared in RAW format, processed by Adobe Photoshop Lightroom.
Canon 5D Mark III vs D3s ISO Comparison at low ISOs
What about comparing the Canon 5D Mark III to the Nikon D3s? Let’s take a look:
Similar to the 5D Mark II, I cannot see much difference between the two cameras at low ISO levels – both perform really well from ISO 100 to 400.
Stopped down to ISO 800, the Nikon D3s looks a tad cleaner in comparison.
Canon 5D Mark III vs D3s High ISO Comparison
Let’s see what happens when both are pushed to ISO 1600 and above:
ISO 1600 also looks very comparable between the two cameras, although the Nikon D3s looks a little cleaner to me. While both were shot at the same exposure, the Canon 5D Mark III image is still a little brighter, which contributes to more noise in the shadows. I tried dialing 1/3 negative exposure in Lightroom, but the D3s image still looked cleaner overall.
At ISO 3200, the Canon 5D Mark III shows more pronounced noise in the shadows.
And as you can see from the image itself, the difference is even more obvious at ISO 6400.
Increasing ISO to 12800 again results in better performance by the D3s, with about 2/3 of a stop difference.
When pushed to ISO 25,600, the Nikon D3s is cleaner and retains colors, while the Canon 5D Mark III is much noisier in comparison. The process of down-sampling the image from 22.3 MP to 12 MP does help the Canon 5D Mark III quite a bit in terms of details, but there is still way more noise throughout the image.
Canon 5D Mark III vs D3s Summary
The Nikon D3s has been Nikon’s best low-light camera since it came out in 2009. When the Nikon D4 came out, I thought it would be about a full stop better than the D3s that it replaced. As it turned out and I reported in my Nikon D4 vs D3s ISO Performance Comparison article, the Nikon D4 pretty much matched the performance of the D3s when images were down-sampled to the same resolution – there was not a full stop of difference between the two. So Nikon pretty much kept the high ISO performance the same but provided more options for resolution at lower ISO levels. Hence, I saw no reason to try to compare the Canon 5D Mark III to the D4 (which I am still waiting for) and I used my D3s for comparison instead.
As it turned out, when properly down-sampled, the Canon 5D Mark III performs quite well at lower ISO levels and only struggles at very high ISOs, where it is up to 1 stop inferior in performance.
Canon 5D Mark III vs Nikon D800 ISO Comparison at Low ISOs
Let’s see how the Canon 5D Mark III compares to the Nikon D800:
At base ISO, both are very clean, with very similar output and detail.
Unlike the 5D Mark II, the new 5D Mark III matches the performance of the D800 at ISO 800.
Canon 5D Mark III vs Nikon D800 High ISO Comparison
Let’s see what happens at high ISO levels above ISO 1600:
Looks like the D800 is a tad cleaner in the shadows, otherwise both show very good performance.
ISO 3200 is clearly noisier on the Canon 5D Mark III, as can be seen from the above image and the grain is a bit larger too (again, mostly due to down-sampling).
And even more so at ISO 6400 – look at the shadows.
The grain throughout the frame is bigger on the 5D Mark III at ISO 12,800, although there is not a huge difference. I would say between 1/3 to 2/3 of a stop max.
Pushed to ISO 25,600, both are pretty similar, although the Canon 5D Mark III still shows larger noise artifacts. Again, down-sampling does the magic for the D800 here!
Canon 5D Mark III vs Nikon D800 Summary
As you can see, the Nikon D800 sensor performs overall better than the sensor on the Canon 5D Mark III. Although the Canon 5D Mark III shows impressive levels of noise at lower ISO levels, it still cannot quite match what the D800 can do when images are normalized to the same print size. Don’t forget that there is also a big resolution difference between the two – the Nikon D800 is 36.3 MP, while the Canon 5D Mark III is 22.3 MP. So at base ISO levels, the Nikon D800 is going to have a resolution advantage for landscape and fashion work. And as I have already shown in the first page of this review, the Nikon D800 also has much more dynamic range in comparison.
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