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What is the spectral response curve (graph) of the EOS R5 sensor?

Bobwithbigbelly
Apprentice

That's the question.

9 REPLIES 9

I'm not sure if this link is permitted here, so if you don't see my link, check to see if they have the info you are looking for at DXOMARK com.

Click here.

Newton

EOS R5, R6, R6II. RF 15-35 f/2.8L, 50mm f/1.2L, 85mm f/1.2L, 100mm f/2.8L Macro, 100-400mm, 100-500mm L, 1.4X.

Bobwithbigbelly
Apprentice

Thank you, but I already saw that and couldn't make head or tail of it. I'm looking for something like these:  Click to show 

Such graphs are easier to find with older more common cameras. Wish Canon had a Gmail so I could contact them directly.

Why you need to know might help answer the question.

While not specific to the EOS R5, these papers compare Canon sensors to other camera brands.

https://arxiv.org/abs/2304.11549

Cite as:arXiv:2304.11549 [eess.IV]

Spectral Sensitivity Estimation Without a Camera

A number of problems in computer vision and related fields would be mitigated if camera spectral sensitivities were known. As consumer cameras are not designed for high-precision visual tasks, manufacturers do not disclose spectral sensitivities. Their estimation requires a costly optical setup, which triggered researchers to come up with numerous indirect methods that aim to lower cost and complexity by using color targets. However, the use of color targets gives rise to new complications that make the estimation more difficult, and consequently, there currently exists no simple, low-cost, robust go-to method for spectral sensitivity estimation. Furthermore, even if not limited by hardware or cost, researchers frequently work with imagery from multiple cameras that they do not have in their possession. To provide a practical solution to this problem, we propose a framework for spectral sensitivity estimation that not only does not require any hardware, but also does not require physical access to the camera itself. Similar to other work, we formulate an optimization problem that minimizes a two-term objective function: a camera-specific term from a system of equations, and a universal term that bounds the solution space. Different than other work, we use publicly available high-quality calibration data to construct both terms. We use the colorimetric mapping matrices provided by the Adobe DNG Converter to formulate the camera-specific system of equations, and constrain the solutions using an autoencoder trained on a database of ground-truth curves. On average, we achieve reconstruction errors as low as those that can arise due to manufacturing imperfections between two copies of the same camera. We provide our code and predicted sensitivities for 1,000+ cameras, and discuss which tasks can become trivial when camera responses are available.

https://arxiv.org/pdf/2304.11549.pdf

https://eprints.ncl.ac.uk/235852 

Estimation of the spectral sensitivity functions of un-modified and modified commercial off-the-shelf digital cameras to enable their use as a multispectral imaging system for UAVs

Lookup NU author(s): Dr Elias Berra, Dr Rachel Gaulton 

This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract
Commercial off-the-shelf (COTS) digital cameras on-board unmanned aerial vehicles (UAVs) have the potential to be used as multispectral imaging systems; however, their spectral sensitivity is usually unknown and needs to be either measured or estimated. This paper details a step by step methodology for identifying the spectral sensitivity of modified (to be response to near infra-red wavelengths) and un-modified COTS digital cameras, showing the results of its application for three different models of camera. Six digital still cameras, which are being used as imaging systems on-board different UAVs, were selected to have their spectral sensitivities measured by a monochromator. Each camera was exposed to monochromatic light ranging from 370 nm to 1100 nm in 10 nm steps, with images of each step recorded in RAW format. The RAW images were converted linearly into TIFF images using DCRaw, an open-source program, before being batch processed through ImageJ (also open-source), which calculated the mean and standard deviation values from each of the red-green-blue (RGB) channels over a fixed central region within each image. These mean values were then related to the relative spectral radiance from the monochromator and its integrating sphere, in order to obtain the relative spectral response (RSR) for each of the cameras colour channels. It was found that different un-modified camera models present very different RSR in some channels, and one of the modified cameras showed a response that was unexpected. This highlights the need to determine the RSR of a camera before using it for any quantitative studies.

https://eprints.ncl.ac.uk/file_store/production/235852/2A11815A-0BAA-4D52-A17A-F866376C58E3.pdf

This paper explains the design of Canon sensors with DPAF: https://www.imagesensors.org/Past%20Workshops/2015%20Workshop/2015%20Papers/Sessions/Session_1/1-03-...

 

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https://www.rsok.com/~jrm/


@Bobwithbigbelly wrote:

Such graphs are easier to find with older more common cameras. Wish Canon had a Gmail so I could contact them directly.


You can go to the Canon USA Support web site, scroll to the very bottom and click the "[+] Feedback" link. They don't make it easy to find 🙂

Canon Support Link-1.jpg

Newton

EOS R5, R6, R6II. RF 15-35 f/2.8L, 50mm f/1.2L, 85mm f/1.2L, 100mm f/2.8L Macro, 100-400mm, 100-500mm L, 1.4X.

johnrmoyer
Mentor
Mentor

Illiah Borg created a spectral response curve for the EOS R3 bare sensor with no lens. I have been told that often the curves are similar for all sensors from a given manufacturer from about the same time period.

https://www.dpreview.com/forums/post/65726551

 

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https://www.rsok.com/~jrm/

johnrmoyer
Mentor
Mentor

How to create your own and some examples.
https://arxiv.org/abs/2304.11549
https://arxiv.org/pdf/2304.11549.pdf
At this link, you may search for Canon EOS R5 and view a graph. So far as I can understand, it is made from the numbers that are used to convert raw photon counts into a color image: https://color-lab-eilat.github.io/Spectral-sensitivity-estimation-web/

I might guess that the measurements made by Canon engineers during the development of the sensor are trade secrets, but the resulting images  are not. So, it might be possible to reverse engineer the portion of the spectrum captured by the sensor that is used for creating color photos. 

 

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https://www.rsok.com/~jrm/

John_SD
Whiz

LOL. Or, as I said yesterday...

 

 

Bobwithbigbelly
Apprentice

@johnrmoyer

So you want to know why I want the spectral graph? It's because I do astrophotography and I want to use narrowband filters with my unmodded camera, which is possible, but I need to know the sensitivity for 656nm (H-alpha) and 500nm (OIII) so that I can buy the right filter. Thank you for the links (especially the "color lab eilat" link) and the long writing.

@FloridaDrafter

Thanks for showing me where to go. Wonder why Canon wants to hide their Gmail.

I will compare what Canon shows me (if they show me anything) with the Color Lab Eilat graph, and I will make a conclusion.

Bobwithbigbelly
Apprentice

There is something wrong with the Canon Feedback links. My antivirus flagged it because it contains a phishing virus and site cannot be reached anyway. I'm not going there.

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