Are you using the EMVA1288 data sheets?
Cocquelin: Yes, but mainly for internal reasons. It really helps us to compare between different cameras. Because we have such a variety of applications within our industry, it will take a lot of time to go through any test or application. Coming back to standards and having some pre-qualification based data on the same measurement brings value regarding our own customers, because they don’t look at all this data. What they’re interested in is the result of the image and if it is working. Everyone has a smartphone and images are all around. Today’s feedback is more linked to pure feelings if it is a good image quality or not. They compare between different camera images and think this one is better than the other. As long as they have a sharp and clear image that you can display they think that they have a good camera. For them, the performance comes from processing and the end result you get from the camera.
Von Fintel: EMVA1288 is a certain quality level which the camera manufacturer should have on their homepages. It makes it easier to make a first choice, e.g. Basler has more than 700 different material numbers alone for cameras. If you’re searching for information in terms of QE or SNR the fixed pattern and spatial noise data gives you a feeling about the quality of the camera. At the moment, EMVA1288 is getting a little bit less important than it used to be. Now there are more important things like how easy it is to integrate, the software (functionalities) you get, or your processing load within the system. We are trying to give more understanding of the overall system performance and how these things work together instead of only saying EMVA1288 data is the one and only. Nevertheless, if you compare cameras to each other, it’s still a good choice for having some indications. Internally we use EMVA1288 in production to see any quality differences we get with the cameras and we use it to evaluate new sensors for new cameras.
Contine: It is also important to consider the lens. The lens and the camera are two separate objects but it’s very important to consider them as a whole an select the most appropriate lens for the given sensor. Depending on the SNR of the image sensor you must select a different kind of lens or, thanks to a proper shading on the pixel, you can have a bigger aperture of the lens. You can easily get twice the light that you have on a different sensor. It’s not only QE, sensor or camera, you have to consider the whole vision system as well, because with a simple trick you can double the light and so you can really double the SNR and get much better images.
What is a better approach: to select a camera manufacturer for all use cases or to identify the best fitting camera per use case from different suppliers?
Cocquelin: All camera manufacturers are trying their best to cover all applications and all needs, but that’s almost an impossible task. Of course, we are working with preferred manufacturers, building long term partnership but it’s really difficult to find one camera manufacturer for all our use cases. That’s why we are having standards: to move in that direction and to be able to build the best system for the application.
What do you think of small and large pixel and how can we use them?
Contine: If you have a lot of light you can use small pixels. The SNR depends on the pixel area and the read noise. If you have a larger pixel you increase the SNR or you have a smaller pixel with a much better read noise. In this case you have the same SNR. So it depends on the noise. The SNR linearly increase with pixel size. The SNR linearly decrease with the read noise. So if you have two electrons instead of one, it means that you have to compensate with twice the pixel size to have similar performance. Most of the time, bigger pixels are more expensive because it’s like renting a house. The base price is per square meter. Users should focus on read noise instead of pixel size unless you really have a lot of light or you need dynamic range. In those cases you need both: lower noise and a high full well capacity that comes with big pixels.