The primary consideration is the tool that most facilitates your work. I’ll pay for a good tool, if need be…
What I find as a programmer is that most of the investigative tools make quick work of figuring out a problem, but sometimes data types and/or algorithms then require significant work to translate correctly to the “production environment”, which for me is now C++… (used to be Pascal, but where did that go…? )
For those of you looking to move to a new numerical computing language, I’d suggest taking a look at Julia. It’s a real pleasure to program in, and extremely fast too.
If you’re building the box, I need to recommend consideration of a small change. The camera is focused on the distance to the slit, and that 12" length may not be long enough to accommodate your lens’ min focus distance. Now, that min focus distance is measured from the focal plane, so take that into account.
My Z6 with the 24-70 f4 min focus distance is 0.3m, so I have a few cm to play with. However my D7000 with the 18-140 is 0.45m, so with that I’m right at the slit-focal plane distance. Time to pull out the macro lens…
That was one of my intentions. I currently have an old Nikon D90 with an all round 18-200mm lens. But the focus distance of that one is ~45cm (18in), and unfortunately, I don’t have a better lens (I’m planning to switch to a Z6 in the coming months 
).
I was also thinking about modifying the build to allow multiple lengths. Or even borrow Lego bricks from my kids to build the box.
Do you know if the inner color of the box could change the results ?
The light from the slit will reflect on the walls, hence the baffle. Painting the walls with flat black paint doesn’t help; it still reflects, but the baffle mostly takes care of it.
I’ve not painted the latest boxes; it seems that if you can get a clean spectrum surrounded by black, you can have bits of light around the edges of the image. I still try to minimize it, as a bright green pixel somewhere will vex the search algorithm in tiff2specdata.
I did my D50 with the 18-200, and I got a profile with max cc24 DE of 1.8. I’m looking at the lens as part of the optical chain to be characterized.
I’ve considered making the diffuser/slit positioning variable, just keep in mind you really need a port on the end that won’t leak light. That’s why my second design made the ends cover the entire box, including the lid. My first box end didn’t do that, and I spent all sorts of time trying to patch it so it wouldn’t leak…
We have a box of Lego “orphans”, bricks and parts that have been separated from their kit. I almost tried that, but I don’t own the contents of that box… 
@ggbutcher , Thanks for such inspiring posts. I plan to build your spectrometer and create profiles for several cameras.
Did you post drawings or dimensions for your design online?
I am looking forward to getting camera profiles made with an RGB lightsource for use with Lightroom.
Thanks,
Thanks for reading this far; if you’re going to build something, make sure you also read this:
And, somewhere in all this I posted instructions on how to build the spectroscope that works a lot better than the original one described in this thread. Here 'tis:
Camera_Profiling_Spectrometer-Build_Instructions.pdf (746.4 KB)
One of the design considerations for the new model was simplicity of construction; I got the use of power tools down to a radial arm saw and a drill. Please be sure you operate these machines safely, including getting some instruction from an experienced individual if you haven’t used either before.
The above post has links to all four posts in the series.
@ggbutcher Thank you for the instructions. I look forward to building and using it.
Your posts and design are beautifully detailed and described. Thank you!
Let me know of any ambiguities or errors in the build instructions. I don’t write so good, sometimes… 
@ggbutcher I see that some spectrometer designs use a collimating lens between the slit and the grating.
And other designs use a collimating mirror. Do you not need that because of the length of your box? Or did you leave it out because of cost? (The one I show above used a 50mm f/2 Pentax objective like old toys I have kicking around too).
Thanks again,
David
The diffusion filter accomplishes essentially the same thing.
Since the diffusion filter cuts a lot of light that’s helpful to doing a precise focus on the spectrum, this is one part I recommend using a proper filter rather than the paper.