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| Sunday, 14 April 2024 | Dereel | Images for 14 April 2024 |
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Manipulating data in the Microsoft space
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Topic: technology | Link here |
I've been running autocutsel for a while now, and it works, up to a point. If I copy something on Microsoft, it automatically updates the clipboard on the machine that runs the rdesktop. If I mark text on an xterm, it also appears in the clipboard. But it doesn't change the cutbuffer in any way, and that's not what I understand from the documentation:
When the clipboard is changed, it updates the cutbuffer. When the cutbuffer is changed, it owns the clipboard selection. The cutbuffer and clipboard selection are always synchronized.
There's this word “own” that I don't understand. But I do understand “always synchronized”, and that's not what I see. Is this a bug, a misdocumentation, or what?
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How to save an SMS
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Topic: technology | Link here |
I've been trying for years to find a way to save or copy an SMS. Based on my almost complete lack of success, you'd think that somebody wanted to avoid it. Even the mobile phone apps that promise to save or forward them don't work for me.
But finally I've found a way to at least save the text, if not the metadata:
Simple, isn't it. You have to love Microsoft.
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Understanding depth of focus
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Topic: photography, technology, opinion | Link here |
One of the things I learnt as part of my cataract operation was the term depth of focus. I know that, right? No, what I know and use is depth of field. And while they're closely related, there's a subtle difference: depth of field is measured in distances, the closest and furthest distance in acceptable focus when you focus on a specific point. I've known this for ever, at least since I started using cameras 60 years ago. The lenses had a depth-of-field scale on the lens, here a Diaxette that looks just like the one I had at the time:
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The top (black) scale is distance, in feet, and the lower (red) scale is depth of field. Here the focus is set to 30 ft (10 m), and the scale shows a depth of field from a little over 20 ft to a little below 60 ft at f/2.8, or 14 ft to beyond ∞ at f/8.
The devil's in the detail, of course, and 14 years ago I found the contradictions enough that I wrote my own program to calculate depth of field.
The problem with depth of field is that it depends on the distance. Depth of focus is measured in dioptres, the correction needed to move the edges of acceptable focus to the prime focus. And that makes sense: it's independent of the distance.
Or is that the definition? The Wikipedia page is currently very vague:
Depth of focus can have two slightly different meanings. The first is the distance over which the image plane can be displaced while a single object plane remains in acceptably sharp focus; the second is the image-side conjugate of depth of field. With the first meaning, the depth of focus is symmetrical about the image plane; with the second, the depth of focus is slightly greater on the far side of the image plane.
The first definition looks like the inverse of depth of field: instead of measuring the subject distance, it measures the object distance. And clearly the claim that the depth of focus is symmetrical is just plain false. At 1:1 magnification the values are the same. And the “second definition” seems to be the same thing. Without formulae the whole thing is too fuzzy to understand. But the formulae presented are just plain wrong: they're formulae for depth of field. The page also stated:
While depth of field is generally measured in macroscopic units such as meters and feet, depth of focus is typically measured in microscopic units such as fractions of a millimeter or thousandths of an inch.
That's clearly only part of the statement, of course. In optometry depth of focus is usually measured in dioptres, so I said so.
So: clearly the Wikipedia page is almost useless. What else is there? The first hit on Google tells me:
In optometry depth of focus is usually measured in dioptres.
That's quite impressive. It's a reference to what I wrote in Wikipedia only a few hours earlier. And clearly it's useless for confirming my claims. How about Gemini?
Q: How do I calculate depth of focus in dioptres?A: Depth of focus (DOF) isn't directly calculated in diopters. DOF is typically measured in linear units like millimeters or feet https://en.wikipedia.org/wiki/Depth_of_field.
That's a quote from an older version of the Wikipedia page! And it uses the term “DOF”, which I always took to mean depth of field. But there are others who disagree. This article, from the US National Institutes of Health, writes:
In theory, only one plane or surface of world can be in focus at one time. However, the eye exhibits a certain tolerance to out-of-focus images, a feature that is known as depth-of-focus (DOF). The corresponding distance range in which the objects are seen “clearly” is known as depth-of-field (DOFi).
Somehow the term NIH sounds appropriate.
And there's more. This paper goes into some detail, and maybe it contains all that I need to know. It refers to human eyes, and interestingly (on page 830) it comes up with a depth of focus of 0.1 dioptre for adult humans. I just need to read it more carefully.
In summary, I'm just as confused as I was at the beginning. I need to check my maths, but it seems that the concepts are poorly understood, and measuring depth of focus in dioptres is really independent of the subject (or object) distance. That's why depth of field scaled work. But measuring the depth of focus by distances from the sensor is not distance independent. Eyes are a special case because the sensor is always at the same distance from the entrance pupil. But even there, the linear depth of focus should not be symmetrical, which should be particularly apparent when using strong auxiliary lenses (say +20 dioptres, bring focus to 5 cm).
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Off the net again!
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Topic: technology, opinion | Link here |
Idly checking ping times today brought a failure: I couldn't ping eureka.lemis.com from lax.lemis.com. Nor anywhere else, for that matter.
Firewall problem? No, a traceroute stopped much earlier than that. Is there something wrong? The block has been routed here for nearly a year, and in May last year I confirmed:
=== grog@eureka (/dev/pts/24) ~ 33 -> whois -h whois.cymru.com " -v 192.109.197.0"
AS | IP | BGP Prefix | CC | Registry | Allocated | AS Name
NA | 192.109.197.0 | NA | AU | ripencc | 1991-05-01 | NA
4764 | 192.109.197.0 | 192.109.197.0/24 | AU | ripencc | 1991-05-01 | WIDEBAND-AS-AP Aussie Broadband, AU
And what do I have now?
=== root@lax (/dev/pts/7) ~ 90 -> whois -h whois.cymru.com " -v 192.109.197.0"
AS | IP | BGP Prefix | CC | Registry | Allocated | AS Name
NA | 192.109.197.0 | NA | AU | ripencc | 1991-05-01 | NA
Gone! An easy enough bug to fix, I suppose. But it means dealing with Aussie Broadband “support” again. The first part (after authenticating myself) will be to explain to the first level support person what I'm talking about. The horror!
| Monday, 15 April 2024 | Dereel | Images for 15 April 2024 |
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Pixel depth of digital cameras
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Topic: photography | Link here |
One of the important parameters of a digital camera is the pixel depth, which determines the dynamic range of the sensor. Fifteen years ago I wrote “I gather that my Olympus [E-510] has only 10 bit pixels”.
Is that correct? Today I went searching and came up with a blank. The best specs page I could find is this page, but it, too, is too polite to say. Why are people not interested? It has much more of a bearing on the image quality than the number of pixels.
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How to copy SMS, again
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Topic: technology, opinion | Link here |
Callum Gibson read my article on how to save an SMS. He has a simpler method: Google messages. That way you don't need Microsoft, just a web browser.
OK, sounds interesting. Off to take a look, but instead of https://messages.google.com/ I was redirected to https://www.android.com/google-messages/. Funny, says Callum, “it works for me”. Still, the page is clearly related, full of advertisements and content unrelated to what I'm looking for, like “With Google Messages, you can customize your experience, ensure private conversations, and enjoy the latest AI features.”. Dammit, all I want to do is to save an SMS with its metadata, like you can do with any sane MUA with a single click!
First, of course, I have to install Google Messages on my phone. Good news: it's compatible with all my “devices” (which in this context I think means “phones”). OK, install. I was given a single line choice of which “device”:
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Damn, that's my old phone, the one I just use for experiments. Ah, but single line windows are modern. Click and you get:
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Sometimes I despair. OK, click on the second one, and receive the information that the app will soon be installed. Wait a while. Nothing. While I was looking, discovered this comment about the app:
December 30, 2019I still don't know what good this app is, but I can never find answers to the noises that are bugging me.
And that was what I wrote on the following day. Further investigation shows that it was already installed on the phone, and it's the standard messages app that I use. Why didn't Google say so? They're supposed to keep track.
So: what next? I couldn't find anything to tell me what to do. Finally, though, found my way through the maze. You have to be logged in to Google to even get the correct link! And that told me the way through the maze of menus on my phone: click on the image of myself (currently) at top right and select Device pairing, which tells me to go to https://messages.google.com/web. And there I get a QR Code and instructions:
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Problem: there is no QR code scanner on the phone:
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I couldn't find a way to use the code. But I did have the option of signing in, and suddenly that worked,
And the results? It looks surprisingly like Microsoft's PhoneLink. But it does have the advantage that I don't have to fire up a Microsoft machine to access it.
So, next step: save the messages. Why would you want to do that?, says Callum. But yes, you can back them up—to Google Drive, the storage medium that has caused me so much pain in the past. And doubtless the format would be unwieldy.
And at the end, I also understood the comment I made five years ago: the thing keeps dinging at me, the noise it makes when a notification arrives. But all I find is information that my phone is linked to a web browser.
So what's wrong here? Clearly the ability to save messages to Google Drive could be useful to some people. But why can't I save them on the current machine? Once again other people are making decisions for me, not the ones I want. It would be so simple just to save the messages, metadata and all, but modern web and mobile phone software seems to ignore the obvious and want to run before it can walk.
So, a comparison of the methods:
| Microsoft PhoneLink | Google Messages | |||
| 1 | Start Microsoft “PhoneLink” and display the message. | Pair phone with https://messages.google.com/web | ||
| 2 | Select text. | Go to https://messages.google.com/web and display message | ||
| 3 | Copy to clipboard with c-c. | Select text. | ||
| 4 | Mark text in xclipboard on the host machine. | Mark text in xclipboard. | ||
| 5 | Save! | Save! | ||
So yes, it could be easier if it weren't for the fact that I have to explicitly pair and unpair. But the noise it keeps making means that I have to unpair when I'm not using it. Why can't they have a button to turn the noise off?
In passing, Callum mentioned another app, SMG Backup and Restore. It still just copies to Google Drive.
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Double bubble
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Topic: health | Link here |
The bubble in my eye is gradually getting smaller, not as fast as I had hoped. This evening, though, I had two after the evening eyedrops! One was the normal bubble, and the other one was a tiny bubble about 5% of the size of the main one. It hung around for an hour or two before disappearing again.
How did that happen? My guess is that one of the floaters kept it from joining the main bubble.
| This page contains (roughly) yesterday's and today's entries. I have a horror of reverse chronological documents, so all my diary entries are chronological. This page normally contains the last two days, but if I fall behind it may contain more. You can find older entries in the archive. Note that I often update a diary entry a day or two after I write it. | Do you have a comment about something I have written? This is a diary, not a “blog”, and there is deliberately no provision for directly adding comments. It's also not a vehicle for third-party content. But I welcome feedback and try to reply to all messages I receive. See the diary overview for more details. If you do send me a message relating to something I have written, please indicate whether you'd prefer me not to mention your name. Otherwise I'll assume that it's OK to do so. |
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