low ISO values

[xpatUSA]

Ted I don't have much time for DXO's scoring system. I prefer to look at their measurements and make my own judgements. This is a link to their ISO measurements technique. It's based on ISO 12232.

Dave

Thanks for the link, Dave. Right away I notice that they omit two methods:

"ISO Standard 12232 defines two ways to measure ISO sensitivity."

Incorrect, see below.

"The first relates sensitivity to the exposure necessary to saturate the camera. The second, seldom used, compares the relative exposures to obtain different signal-to-noise ratios. The more common saturation-based method is described below."

That method is increasingly less common, IMHO.

From 2006, ISO defined four ways to measure ISO sensitivity (five, if you count two levels of noise-based), but DxO seized on saturation-based, a method that seems to be going out of favor with camera manufacturers, including the mighty Canon.

Totally untrustworthy . .

[DanK]

Dave,

Yes, what I have found so far indicates that it is nothing more than an EV adjustment, which is what exacts a price in DR (at the highlights end). You can see the DR results for the Mark II here: https://www.dpreview.com/reviews/canoneos5dmarkii/25

[dje]

Thanks for the link, Dave. Right away I notice that they omit two methods:

"ISO Standard 12232 defines two ways to measure ISO sensitivity."

Incorrect, see below.

"The first relates sensitivity to the exposure necessary to saturate the camera. The second, seldom used, compares the relative exposures to obtain different signal-to-noise ratios. The more common saturation-based method is described below."

That method is increasingly less common, IMHO.

From 2006, ISO defined four ways to measure ISO sensitivity (five, if you count two levels of noise-based), but DxO seized on saturation-based, a method that seems to be going out of favor with camera manufacturers, including the mighty Canon.

Totally untrustworthy . .

Ted I don't know when the DXO article was written. But I'm sure they have enough technical expertise to know of the updates to the ISO standard. Maybe they still consider the Saturation method the most scientific? I don't know.

Dave

[xpatUSA]

Ted I don't know when the DXO article was written. But I'm sure they have enough technical expertise to know of the updates to the ISO standard. Maybe they still consider the Saturation method the most scientific? I don't know.

Dave

Yep, it's all very puzzling, Dave.

The Standard that I was referring to is ISO 12232: 2006.

One might think that 11 years is enough for them to catch up, but maybe not so ...

I have a bad feeling that the most popular Method currently is the 'Recommended Exposure Index' (REI) which is where manufacturers, after their "testing:, decide what is the best ISO rating for your camera. Pathetic hogwash, as far as I am concerned . . .

[Manfred M]

Good find.

As to DxO's saturation-based measurement, I've read that Canon has changed to something like the SOS method which allows less headroom.

Personally, I'm rarely happy with DxO's dumbed-down metrics but that is just a personal view, sorry. Still smarting from being told here that DxO is the "industry standard" as if nobody else's measurements mattered (wasn't you, Manfred!).

Ted - the one thing that DxO brings to the table is a consistent comparison of cameras. This is probably of more interest to most users than the arguments over how accurately the tests comply with specific ISO criteria.

This is really no different than say the EPA fuel economy tests. We know that these are based on idealized conditions that no vehicle being used under "real" driving conditions will ever meet. But the results will at least allow a consistent level of comparison between a number of different vehicles. A vehicle that gets 17 mpg city versus 22 mpg city; the 22 mpg vehicle is likely going to be cheaper to run if I only consider the fuel costs (assuming both use the same grade of fuel). If the car companies provided their own fuel economy ratings, we would unlikely be able to have any confidence in the published fuel economy ratings. Let's face it, the vehicle manufacturers are going to "game" the system by tuning the vehicles to operate as efficiently as possible for the test conditions.

So long as we recognize the limitations of the data, we can glean some information that will be useful to the majority of users. On the other hand, if I were buying this equipment for a specific technical purpose, the data might not be particularly useful to me and I might have to evaluate the equipment quite differently, rather than relying on test data from a source like DxO.

The only significant concern that I see is a change in test methodology. That would change the baseline and the test results from before and after the methodology change could no longer be directly compared. I suspect this is why testing organizations like the EPA continue to use the tests, even with the known flaws and oversimplification of the results.

[xpatUSA]

Ted - the one thing that DxO brings to the table is a consistent comparison of cameras.

Manfred: are you suggesting that DxO is the only camera/lens tester that brings to the table a consistent comparison of cameras. Are there others?

[ISO generality is probably of more interest to most users than the arguments over how accurately the tests comply with specific ISO criteria.

My post was directed to @dje by name. We were not arguing. Whether he is part of "most users", I have no way to know.

By measuring only the saturation-based ISO Speed, DxO is actually standardizing all test cameras to meet their single test method. These days that seems to the least popular actual method with manufacturers (I speculate), and so many or most of their ISO tests will not be correct for the camera involved. If most users are happy with, so be it. Others are probably a little more interested in how their cameras work.

For those "least users" who may be interested, here's ISO's table of tolerances for the various methods:



The red is from a previous post; the differences between the methods are of interest to me and possibly a few others here.

"most users" will be uninterested in the content, if I understand Manfred correctly.

Manfred, the strength of your rebuttal of my post to another member gives me again the impression that technical or minority content is unwelcome here - on the grounds of being of little or no interest to "most users". Should I include a caveat in any such post in future, so as to avoid your comments on what "most users" want or understand?

[Manfred M]

Manfred, the strength of your rebuttal of my post to another member gives me again the impression that technical or minority content is unwelcome here - on the grounds of being of little or no interest to "most users". Should I include a caveat in any such post in future, so as to avoid your comments on what "most users" want or understand?

Ted - it may have been directed at a specific member, but as your posting was in an open forum, it was there for all to read. You presented one side of an issue and I presented a different viewpoint. I'm not sure why you consider it a rebuttal; both of us made valid points, I think.

As someone who has a technical background, I am indeed interested in these technical aspects of photography, although frankly not necessarily at the level of detail that you do, at least in the subjects that seem to interest you. My background as a mechanical engineer is more in product design and manufacturing. This means I am less interested in the subtleties of how the electronics work than someone of your background is. I am more interested in the ergonomics, construction and design of the mechanical elements of camera and lenses.

That being said, what is most important to me is probably what is most important to many of the members of this site; getting good images. Photography is an "equipment sport", so having a basic understanding of how cameras and related photographic gear is "table stakes". Getting a good image requires not just the technical knowledge, but also the knowledge of how to organize a scene and to make an emotional impact on the viewer.