Ban Resolution

Author: John Honovich, Published on Feb 18, 2013

The word 'resolution' should be banned in surveillance. What all IP manufacturers mean when they say 'resolution' is 'pixel count.' We should be clear and precise, calling it what is - pixel count - to avoid confusion and making important mistakes.

Two Meanings

Traditionally, resolution meant the ability to resolve, or see, details. This focused on the user and the ability of the device to deliver meaningful visible benefits.

Now, resolution means the number of physical pixels that a sensor has - 1 million pixels 'resolution', 3 million pixels 'resolution', 10 million pixels 'resolution'.

What's Missing

Pixel count is only one element in a camera's capability to deliver visible details. Other critical ones include lenses, compression, frame rate, low light and WDR performance - some of which actually can be worse with more pixels. As such, resolution as 'pixel count' ignores critical elements in delivering real 'resolution'.

Height in Basketball

Pixels are like height in basketball. If you are too short or have too few pixels, you can never be the best at either. But being the tallest or having the most pixels does not ensure success. In basketball, a very tall person might lack coordination, athleticism, drive, intelligence, etc. just like a super high pixel count camera might be terrible in many other ways. More pixels can be useful but, just like height in basketball, smart 'scouts' should consider the whole package.

Call it Pixel Count

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A simple solution would help a lot. Stop using 'resolution' and start saying 'pixel count'. Then users and specifiers can think more clearly what more pixels actually delivers.

For more on image quality, see our tutorials on resolution, PPF, WDR, lenses and compression.

'Real' Resolution Tested

By comparison, see our real resolution test using ISO TV line counts.

Comments (40)

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Videoimage quality—suitability for the viewing task—is what the Video Quality in Public Safety initiative is about, which has developed a number of resources including an online Guide to Defining Video Quality Requirements. This is an online tool that follows a defined process for developing camera requirements, including lighting.

The guide is great John, I especially appreciate that you carefully point out that there is much more to consider than just PPF-calculation. And your approach to specifying and testing earns you respect. However – I’m aware about the industry is going towards PPF but this puzzles me somewhat since the method is lacking so much of accuracy. There should be other methods or performance specs that camera manufacturer could develop or use.

Let me try this theory with you and the other forum readers.
The “old” testing method with test target showing the horizontal TVL resolution is actually giving a more or less exact measurement of the image resolution (both live and recorded). Wouldn’t it be a perfect specification for the manufacture to present in product sheets which different TVL resolution (total/whole width) the camera can perform depending on which compression is used/set (this should be easy for the manufactures). Then you would be able to calculate TVL per Foot instead.
Then of course you still have to consider many of the other issues regarding facial angle, light etcetera but that is another problem to address…

Audio had the exact same problem when VoIP was introduced and what we ended up with was Mean Opionion Score (MOS)

http://en.wikipedia.org/wiki/Mean_opinion_score

My point is that no matter what, video will remain subjective and the statistics and data will help, but the uses of video are so diverse... As always, your mileage will vary...

John, You can't change HISTORY, resolution is here to stay, its left over from the Days of Television, the Indian Resolution Pattern. It won't go away untill all the old timers are gone or the manufacturers start using Pixel Count in there marketing literature.

Ray, thanks for sharing the VQIPs documents. They look revised in the last year. Unfortunately, the overall vagueness and scatteredness of them makes it hard to understand. I think IPVM should prepare a free public 101 image quality guide to help end users.

Jan, you could use TVL for IP cameras but there are still some important shortcomings: The results would still be dependent on light levels (just like analog) so a camera good at ideal lighting might be weak at low light or WDR scenes. Plus, it depends on the compression level set and manufacturers would certainly game it for as low as possible to maximize their TVL rating, even if that compression level would rarely if ever be used in production.

Luis, it is history but it's more than history. The biggest part of the problem is that the word 'resolution' means so many things in the English language that it is inherently confusing to use.

It seems to me that this is just the tip of the iceberg. Unless I'm just not good at it, it seems almost impossible to me to get any real gauge on how good a camera is going to be in certain conditions just by reading the camera spec. Obviously you can normally get some idea as to whether a camera is going to be completely unsuitable by looking at things like minimum scene illumination, resolution, colour only/day night etc.However seems that there are very few items on a standard spec sheet that are a real measure of how good the picture is going to be when you get the thing on the ceiling.

There are also a lot of other terms which are very confusing and marketing orientated. I use a lot of Axis cameras, I really like them and we get good results from them. I'm using them as an example here just because I know them and not because I think that they are particularly guilty of this.

Lightfinder - Isn't this just a super-sensitive sensor (which is partly because it's bigger than it was before) with a very good image processing chip? Wouldn't it be nicer if we could have a real gauge on how sensitive the sensor actually is. Something akin to ISO on a DSLR camera would be a good start

P-iris - Isn't this just an accurate iris with some good algorythms for working out what F-stop is going to give the best image? Wouldn't it be nicer to say that the iris is accurate to 0.1 of an F-stop with algorythms that take into account depth of field, image brighness and gain level.

As it is I have no way to know if an Axis lightfinder p-iris camera is going to be better or worse than a camera from another manufacturer because they don't have these terms. Don't even get me started on WDR!

In my experience you can't really tell if the camera is going to be great or merely acceptable (at least I can't) just by looking at the spec. I find that the only way that I can really get a good idea of what cameras to use is to stick to manufacturers that I trust and to try cameras out in a similar environment before I spec them.

Neil,

I disagree only about the P-iris. The P-iris is conceptually different from DC iris. With a DC iris the camera do not know the iris position because it is based in a galvanometer without feedback sensor. The camera only knows if the image level is too high or too low and try to open or close the iris, but there is no way to the camera know the actual aperture of the iris. With the P-iris, the iris control is based on step motors that allows the steps to be counted, so the camera has more precision and can know the actual position and use the algorythms to choose the best configuration.

I hear what you're saying, John, but I think there is more to say about it.

While I do not know if this was the right forum / thread to discuss what anyone should do, or what options are available. Based on the topic "Ban Resolution" I would be inclined to agree with you if there were no other options - but I am sure that there are indeed. We who are working on this at the professional level must somehow ensure that manufacturers are doing what they can to improve the situation. Not least you John, and IPVM, has in an exemplary manner pointed out shortcomings and misleading marketing of manufacturers, distributors and others and that I think is very important and I encourage you to keep on doing so.

And forgive me now because I'm stubborn, but I think you need to split the elephant into smaller pieces. First, determine the visible resolution a camera can perform - then you have basic conditions to relate to (and the horizontal TVL resolution is visually exact (and light conditions doesn’t affect that), pixel count is not). Thereafter you can take lighting conditions, etc. into account. And there are standards and norms that support my argument (but actually also the pixel count in the latest European standard).

You will find, for example, IEEE standard for measuring video resolution here (almost for free ;-). http://ieeexplore.ieee.org/xpl/mostRecentIssue.jsp?punumber=3275

Neil, thanks for raising a number of very interesting points. My feedback:

  • I agree: "It seems almost impossible to me to get any real gauge on how good a camera is going to be in certain conditions just by reading the camera spec." A few metrics can help - if the sensor is too small (1/4" or less) or the F stop is too high (f/2.0 or higher) but overall it's hard to tell just by reading. You need to do test - either yourself, IPVM tests, etc.
  • On Lightfinder, Axis' low light enhancements are legitimately impressive (see our Q1602 and Q1604 test results that compare side by side to competitors). That said, lux ratings just can't be trusted - even if Axis was 'truthful', many other manufacturers are not, making it impossible to compare (see Don't Trust Lux Ratings).
  • As for P-Iris, our P-iris test results show it does not make much of a difference, even if technically it's implementation is more precise than auto iris.
  • For WDR, we have 3 test reports that can help you - the 2013 WDR shootout, the Megapixel WDR shootout and our original 2011 SD vs MP WDR shootout.

Let us know if you have other questions or feedback.

John, I agree about the VQIPS web pages not having intuitive user interaction. You said, "I think IPVM should prepare a free public 101 image quality guide to help end users." I'd be in favor of that.

One of the things I like about the VQIPS initiative is that they are collecting image examples and I think a collection of real scene images at various example resolutions (oops!) would really help. Like you, I am a big fan of field testing and each time I am considering a new technology I do a field test on it in the target environment. But I like to have a good starting point and be able to do the test only once! So that's where a good set of example images to use as standards would help, I think.

Focus is a big issue, along with depth of field, and I have seen many projects where cameras that were capable of doing the job were focused in bright daylight (long depth of field) and had target scene areas out of focus once the light levels started dropping and the auto-iris opened up. I think that good "before" and "after" examples of right focus and other elements would be very helpful.

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