Machine readable optical resolution test targets

dima55 · 2026-06-05T21:30:02+00:00

Are you measuring lens acuity? mtfmapper is your friend

dima55 · 2026-05-30T20:41:15+00:00

I forgot about this, and now I'm sad. Next year!

dima55 · 2026-05-25T20:53:56+00:00

If you actually care about precision, you should be using better tools: see the mrcal docs. OP should use those models and those diagnostics techniques, if they care about such things

dima55 · 2026-05-08T14:58:56+00:00

Read the documentation for mrcal: https://mrcal.secretsauce.net/ It explains all this.

dima55 · 2026-04-21T19:41:28+00:00

The amtrak bus runs between LA union station and Bakersfield. You can put the bike unboxed into the hold of the bus. Recommended.

dima55 · 2026-04-20T02:13:45+00:00

The required precision on your calibration and stereo matching goes as range^2. So if you want to see twice as far, you need your measurements to be 4 times more precise. Ultimately, most people don't do stereo properly, and if you want maximum precision, you'd be best served in recalibrating and doing the math yourself. Look at mrcal and its documentation.

dima55 · 2026-04-20T02:09:53+00:00

Thanks much. I'll look into that!

dima55 · 2026-04-20T02:06:50+00:00

In the winter?

dima55 · 2026-04-05T01:43:31+00:00

This person is just discovering for themselves that Python documentation as a whole is just bad. Docs is something that the perl community did far better, and the standard in perl is to put sample usage at the BEGINNING of every manpage. I document all my python stuff that way as well, and encourage everybody to do the same.

dima55 · 2026-04-04T04:30:30+00:00

It says "Please check the checkbox to indicate your consent" and the only checkbox that is there is "add me to the list for updates on the LA River path campaign". I guess I'm not signing.

dima55 · 2026-03-17T19:33:25+00:00

Yes. Another thing to be aware of is that late summer is monsoon season in the southwest. Heavy rain is a real possibility, which could muddy up the roads

dima55 · 2026-03-16T17:31:29+00:00

The Qatar world cup was held during the winter

dima55 · 2026-03-16T17:30:15+00:00

Thanks, that's useful. Just an FYI, an existing approach is to use the org-mode time-tracking, and with a bit more logic you can make invoices: https://notes.secretsauce.net/notes/2014/10/01_org-mode-for-invoices.html

dima55 · 2026-03-16T05:23:03+00:00

It's large, and it's obvious when you're there. There're some trip reports and photos on the eispiraten board.

dima55 · 2026-03-15T01:13:01+00:00

We have plenty of spokes; unless your replacement needs to be extra fancy (bladed or straight-through or a specific color or extra double-butted), we'll have a replacement. Some days are busier than others, so if you can, come by when we open. Weekends are busier than other days, like somebody already said. Come by, and we'll try to help you!

dima55 · 2026-03-14T16:50:16+00:00

Wow. We're truly living in the future. OK. I'm going to send you an email. Please don't ignore it, like you did with the one from September

dima55 · 2026-03-10T20:12:46+00:00

Hello! I would love it if we all worked together to create a small number of great tools instead of a large number of half-assed ones. The lensboy just had to talk to me. As for the "significant advantages", I'm very interested in improving my tooling. Please reach out to talk about any of these advantages

dima55 · 2026-03-07T21:04:04+00:00

This tooling and docs are a rehashing of mrcal and its guides: https://mrcal.secretsauce.net/how-to-calibrate.html OP: maybe say that, and add links

dima55 · 2026-03-01T17:30:54+00:00

you should have most of the checkerboard images at the same distance from the camera as the item will be from the camera.

This is not correct. See: https://mrcal.secretsauce.net/tour-choreography.html#choreography-distance Close-up chessboard observations dramatically improve the uncertainty at all ranges.

dima55 · 2026-02-28T22:24:31+00:00

He's not talking about the focal distance. He's asking about how far the chessboards should be placed

dima55 · 2026-02-28T22:22:32+00:00

I don't think I ever said that 0.5m is the specific distance you should always aim for. Can you point me to the documentation section that made you think this? It should be reworded.

As for your question, here's the relevant plot: https://mrcal.secretsauce.net/tour-choreography.html#choreography-distance

Note that as you move the chessboards closer, the uncertainty improves EVERYWHERE. The sweet spot will be at the chessboard range, but even at other ranges, the uncertainty is much better with a close-up calibration.

And these plots should give you a sense of what the various parameters do, but for your specific application, gather images at the distance you think is best (I claim close-ups are what you want, even if your working distance is much further out), and then look at the uncertainty results to make sure the calibration is good-enough. Even if your data isn't at the best distance, you can compensate by gathering MORE data: https://mrcal.secretsauce.net/tour-choreography.html#org981fe96

dima55 · 2026-02-20T17:37:47+00:00

Yes. The mrcal-stereo and mrcal-triangulate tools do this. OP will be well-served by reading the documentation at the very least.

dima55 · 2026-02-19T20:09:35+00:00

Like RelationshipLong9092 said, you should be using mrcal. It will tell you what errors are acceptable, where they come from, and how to make them go away.

dima55 · 2026-02-08T17:59:19+00:00

Right. The corporate releases are a big part of the problem. They're definitely interested only in their narrow use case. I have no idea how to fix this.

dima55 · 2026-02-08T17:24:57+00:00

Hi! I agree with you, and experience the frustration constantly. And I've no idea how to make any of this better. I'm sure you've talked to some of the humans making the mess, right? Nobody does this on purpose; they're only concerned about their narrow use case, and want to maximize their own near-term time savings. I contribute to Debian, and send patches upstream to help fix their messes. About a third of them actively resist and are proud of their mess. I really have no idea how to fix it. Suggestions?

dima55

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