70D Dynamic Range is actually great, despite what DXOMark says

Started Jan 21, 2014 | Discussions thread
rwbaron Forum Pro • Posts: 14,210
Re: 70D Dynamic Range is actually great, despite what DXOMark says

David Hull wrote:

rwbaron wrote:

David Hull wrote:

Just another Canon shooter wrote:

David Hull wrote:

So here is a question for you: As you say, the effective system noise (camera noise, if you will) is higher at ISO 100, so tell me how Canon would fix it. in other words, based on the DxO data and the Sensorgen information based on it, what part of the Canon architecture needs to be improved?

I called that read noise, not system noise, and they should improve the readout circuit. It is trivial and not worth discussing.

When you measure it, you do not know where it is coming from (but we have additional info indicating what is going on). What Sensorgen does it to model it as additive noise and a multiplicative one, and fit a curve. Then they report the additive noise as "read noise".

He isn't really modeling anything, he is taking the DxO information and presenting it in a different perspective, one which makes it a bit easier to see what is really going on in the camera. It is certainly read noise but it is not coming from the sensor, it is not trivial and it IS worth discussing for those who want to understand what is really going on in the camera. If you want to understand that DxO DR curve and why it looks the way it does, you have to take the time to understand the camera's electrical implementation, the noise line up etc.

I think one of the things that Canon grapples with is that they do have a very good sensor technology (and have had it longer than anyone else). Their chosen implementation is sub par to the competition in two areas which manifest primarily at low gain settings. However, at the other end (where probably the bulk of people use the camera) they are fine.

Some of us want to know the why behind the what, for those it probably IS worth discussing. My point was simple, the sensor is just part of the imaging system, and in the case of Canon, it does not appear to be the root cause of the low ISO deficiencies that everyone like to point out in these threads.

David,

I wonder if Canon might implement a work around for this problem. From what I've seen of the early implementation of Magic Lantern's dual iso it looks very impressive. I've not taken the time to fully understand Canon's 20 MP dual pixel sensor but possibly they could implement a better dual iso capability and still maintain full resolution but maybe I've missed something about that sensor's design. I'd rather have the cleaner signal and extended DR at low ISO but if dual iso can be made to work as well or better for the same purpose and not sacrifice resolution then I'd be perfectly happy. One forum member has ML's dual iso loaded in his 5D2 and has made some ISO 100 comparison's to his D600 and the 5D2/ML results look better IMO. The downside is there's some loss of resolution but he isn't concerned because detail in shadow content isn't that obvious.

Bob

That seems like more of a Band-Aid approach to me. Hopefully Canon will come up with something a bit more elegant like Sony did. I really think that Sony was trying to address the pattern noise issue more than achieve wider DR. I think this was probably driven by their professional broadcast clients rather than still photographers.

The ML dual ISO examples I've seen are pretty impressive and it's in it's infancy from a free developer.

Knowing large companies I've wondered if it wasn't just driven by cost reduction and component simplification. You know much more than I but it would seem a big advantage to Sony from a cost, design and layout standpoint to eliminate the off chip ADC especially when making as many as they do and the reduction in pattern noise was just a side benefit. Good selling point against the competition.

It's interesting to me that for all the hoopla over this issue on the tech related photo forums this doesn't appear to be affecting Canon, Nikon or Sony sales. Canon seems to be selling as many DSLR's as ever and appears to have even regained some market share in the pro ranks with the 1DX. It blew me away to find Photoshop RAW file guru Scott Kelby recently switch from his D4's to the 1DX. If anyone would be sensitive to this issue I would think he would be.

Bob

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