EOS 5D MARK3 - Noise issues at low ISO and Highlights Priority On

Wednesday, 1 May 2013
eos5d-markiii-ef50mmI have an Eos 5D Mark3 since few months, it replaced the Eos 5D2 I used in India that had partially left me because of poor weather sealing giving problems to the contacts. I always judged with some reservation the image quality of the 5d line , coming from the 1Ds mark2. These cameras do produce excellent images, but some  really bizarre problems in cameras of this level do continue to appear.
Already in the Indian photos, taken with Eos Eos 40D and 5D Mark2, I started to notice some strange things: the old 40D held up much better than the other when some overexposure of the shadows is applied in ACR, without altering the overall exposure. The Eos 5D Mark2 had often noise in the shadows at low ISO, even 100, a noise made of stripes (vertical banding), as the image from a fax.
I have not changed the Mark2  because the camera was broken, the problems with the contacts were resolved immediately by the excellent Canon Service Center in Rome. I decided to change it for many reasons, starting from the AF, a most versatile one,  but also for a significant improvement in the well-known problems of noise, at least as for these already seen in the EOS 5D2. A general upgrade in short, without waiting for miracles but certainly hoping for a more complete and versatile camera for all uses, eg. also for sport, in which the Mark2 was very lacking.
I have not used much so far Mark3, until recently I did a photo shooting for a wedding, with intensive use of this camera, always mounting a 50mm fixed on it. Aside strange behaviour AF due in part to the lens but that I did not expect, the AF was not very responsive, very slow in certain situations, but what has made me very suspicious is the image quality.

I’ll make it short, then I will expand this post as soon as I check AF behaviour in better ways. As for image quality, it seems to me that it is on part with EOS 5D2, which is "embarrassing" for a camera costing 3000 Euros. The amount of noise at very low ISO is too much. I have then identified the problem in the "Highlight Tone Priority", which I always keep active for the rare occasions when I have to shoot directly in Jpeg and I want an higher compression of the highlights. My photographic technique pushes a lot towards the highlights to get more detail in the mid-tones and a compression of highlights in a manner I had with certain films I used always seemed helpful. I Imagined that the RAW, of course, did not mind this step (apart from the stop of ISO, ISO 100 becomes ISO2oo) so I kept the function always active. It was a mistake. By shooting in RAW and using ISO 200 but without optimization, significantly improves the quality of the shadows.

Here are two 100% crops from one with and one without the Highlight Tone Priority. Both are open in ACR and Photoshop without any noise reduction or sharpening mask. The photos were overexposed +5 stops to pull out the noise in the blacks. Photo cap was closed. The results speak for themselves:


Evidently something happens, beyond the increase in the level of ISO, in the image acquisition, with a compression generating noise in the blacks at a much higher grade than the values ​​based on the same ISO. This function simply ruins the photos. In principle, just stay below the limit of the highlights, maybe 1/3 stop less for safety, but without compression in the highlights, and then you can proceed in the digital darkroom to the optimization of lights and shadows.

The demon of suspicion was not yet satisfied. Something disturbed me yet, this time I did the same test with the old and glorious EOS 40D! Same procedure, the same boost +5 stop in postproduction. Here are the results:


Apart from the larger grain due to a relationship between photodiodes and sensor’s surface (which obviously has an impact on the detail level), I do not think there's much to say. The old Eos 40D keeps holding the noise in the shadows better than the new professional EOS 5Dmark3 costing 3000 euro. Even the 40D is a lot worse with the Priority active but at the same settings the results are better with the 40D than the EOS 5D Mark3! Then EOS 5D3 resolves more detail in real images, so this difference is negligible. If my camera has no manufacturing defects, such a result is demeaning.
As final note  I’m not saying that the EOS 40D is a better camera, I just say that if we consider the shadow recovery at low ISO alone, EOS 5D3 is quite mediocre. This does not imply it makes mediocre images, not at all. Of course nobody makes pictures with the cap on and nobody needs to recover up to 5 stops of lights. But we know one thing: all in-camera optimisations ruin photos instead of helping, I see this as a big issue especially for those using the camera for video.
©2013 Marco Palladino – All rights reserved

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