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Thursday, 13 June 2019 Dereel Images for 13 June 2019
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Time for an LED flash?
Topic: photography, opinion Link here

One of the issues with my focus stacked photos of the Schlumbergera is the wear aspect: how many photos can you take with a flash tube before it dies? It's easy to take a couple of hundred frames to build a single image. How long would a cheap (or even expensive) flash unit last under those circumstances?

So how about revisiting LED lights? Did a bit of research on eBay and elsewhere and discovered the Travor RF-550D ring light, a device without a manufacturer who wants to own up to it. I also haven't been able to find trustworthy reviews. The Amazon customer reviews are what you might expect: “too bright”; “not bright enough”. Clearly the first of these were written by people who haven't RTFM: you can adjust the brightness down to 1/32, and if the claimed guide number 15 is correct, this would reduce it to 2.7, which would give f/16 at 17 cm. But I have a sneaking suspicion that the guide number is specified in feet, which means a real guide number of 4.6, even weaker than the Olympus STF-8, and an issue if you go beyond, say, 50 cm distance.

Still, the price is right: $36, so I ordered one. We'll see if that is any easier to use.

Fixing CJ's DID
Topic: general, technology, opinion Link here

Called up MyNetFone support today to ask about changing the DID for CJ Ellis' phone. This time I timed things. 3 whole minutes of various announcements, and then the confidence-inspiring male voice “currently our wait times are”, then in a stressed female voice “25 minutes”. So I was able to request a callback, which took another minute, because they were too polite to assume the number on which I called (one of their numbers), and then they wanted to read it back to me and get me to confirm.

It didn't help much. They didn't call back, so after a couple of hours I took another look. Was this confirmation code really for a call back on the old number? I have the old ATA, so it was worth plugging it into the network (behind NAT) and see if it works. Yes! Tried again, but received no call.

Then I took another look at the configuration display:

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That wasn't quite the same as the display. There the number was above the What is a DID? line. Maybe an Overstamped Caller ID is something else. Tried “Add DID”, but it told me I had no numbers.

OK, what happens if I remove the DID from the other number? Potentially I lose it. But basically I had nothing to lose, so did that, added it to the new number, and finally I had:

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And that worked. A good thing too, since it's almost impossible to get to MyNetFone support.

Topic: photography, opinion Link here

I've heard a new FLAT (Four Letter Abbreviated Term) today: DSLM. As I guessed from the context, it expands to “Digital Single Lens Mirrorless”.

What a stupid term! We already have “MILC”, for “Mirrorless Interchangeable Lens Camera”, a term that is better but not good: it applies to all old Leica-like cameras as well, though that's not the intention: like most digital cameras, they all have electronic viewfinders. I personally liked “EVIL” (“Electronic Viewer, Interchangeable Lens”), but it seems that that is too whimsical for certain Christians and people with no humour, though it does offer the advantage of being expandable to “DEVIL” (D for Digital, of course).

But somehow current terms don't make sense. “Mirrorless” isn't a description of what the camera has, it's a description of what the camera doesn't have. DSLM has only the marginal advantage that it sounds like DSLR. But why “single lens”? It would suggest that the lens is not interchangeable, quite the opposite of the intention.

OK, I'll have to give up on EVIL. But what would make sense? Digital is not important enough to mention. Single Lens has no meaning any more. Mirrorless is a negative feature. The things do have electronic viewfinders and interchangeable lenses. Interchangeable lenses will remain a distinguishing feature; electronic viewfinder won't. But try as I might, I can't think of a better description than EVIL. Maybe rearrange the letters? VILE? LIVE? “Lens interchangeable, viewfinder electronic”? None really work. Maybe retrofit “MILC” to mean “Modern Interchangeable Lens Camera”, then gradually drop the M?

Friday, 14 June 2019 Dereel Images for 14 June 2019
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Arum buds
Topic: gardening, photography, opinion Link here

There's an Arum in front of the laundry, and it's just coming into flower. But how to photograph it? Clearly I wanted the background out of focus, something that the “full frame” people think that they have invented. So clearly I need a wide aperture lens. The Leica Summilux 25 mm f/1.4?

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Maybe this is one of the few cases where I could do with less depth of field. Before I go and buy an extreme f/0.95 or even f/0.85 lens, how about longer focal length? The M.Zuiko Digital ED 75 mm f/1.8, which I bought a year ago and have hardly used? Bingo! Finally a use for the lens:

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I like the tips of the flowers.

Offending Christians?
Topic: general, technology, photography, opinion Link here

Yesterday I wrote:

I personally liked “EVIL” (“Electronic Viewer, Interchangeable Lens”), but it seems that that is too whimsical for Christians and people with no humour, ...

A gentle rebuke on IRC from a Christian participant. Yes, that's valid. I have nothing against most Christians, just the militant kind who tell me how to live my life. Like most adherents of other religions, most are good people. Sadly there are too many people of any religion who use it like a weapon and thus do discredit to their religion. “ISIL” comes to mind for the Muslims, but there are certainly too many militant Christians too.

In the case in point I was thinking of the people in the FreeBSD project who decided that the logo was unsuitable, and changed it. Here before and after.



The former image is copyright Marshall Kirk McKusick, and the latter of the FreeBSD foundation, which stipulates, inter alia:


The punctuation is original. I interpret the first stipulation to include not removing the indent (which looks silly) nor the size. But then, this is probably the only time I will use this logo. The second stipulation clearly doesn't include Kirk's emblem, which predates FreeBSD and doesn't belong to it.

But then, that's only part of the pain. The log archive is in ZIP format and has spaces in the path names! What a pain just looking at them! Fortunately nothing in the conditions prevents me from assigning a sane name. O tempora! O mores!

Clearly little of this has to do with Christians. I've changed the article to read “certain Christians”.

More web page mods
Topic: technology Link here

From time to time I quote web pages, which don't always play nice with the their title. For example, the NOAA Solar Calculator has a heading “ESRL Global Monitoring Division”, which doesn't help much. And when I quote from my diary I get (for example, for this month) “Greg's diary--June 2019”.

That could be easier. Each article in my diary has its own URL fragment (the part after the # symbol), a coding of the date and time when the article was written. For some time now they have had their own title, like this one, “More web page mods”. Why not put that in the window heading?

I had this bright idea of an auxiliary file with an array of fragment (index), title and topics. Read it in at the beginning of the page, use the fragment to get the title, and simultaneously build up a new array to write out at the end. That way I wouldn't need to do anything special to keep it up to date. It would also allow me to create an index for the page, though with in the order of 100 articles per month it's not clear how that would work out. I can't think of any use for the topics, but it's cheap and a use might appear.

Problem: it seems that there is no way for the page to know what fragment the client has passed. Damn! After a while, though, it occurred to me that I could include the title directly in the URL, so this page, instead of having the URL, would have the URL The page could then extract the subject parameter and use it in the heading.

That proved to be surprisingly simple, only about 10 lines. Do I now need a list of topics? That would also not be that difficult.

Panic! on teevee
Topic: technology, multimedia, opinion Link here

While watching TV this evening, the screen went blank. Only relatively briefly; then I got a startup display. teevee had paniced!

That almost never happens. It had been up for 47 days, thanks mainly to the solar electricity system. What caused it?

Jun 14 21:34:09 teevee savecore: reboot after panic: page fault
Jun 14 21:34:09 teevee savecore: writing core to /var/crash/vmcore.4

OK, that shouldn't happen, so it's worth a look.

=== root@teevee (/dev/pts/8) /var/crash 4 -> kgdb /home/obj/eureka/home/src/FreeBSD/svn/stable/11/sys/GENERIC/kernel.debug vmcore.4
GNU gdb 6.1.1 [FreeBSD]

Unread portion of the kernel message buffer:

Fatal trap 12: page fault while in kernel mode
cpuid = 1; apic id = 01
fault virtual address   = 0x0
fault code              = supervisor read data, page not present
instruction pointer     = 0x20:0xffffffff829d83a4
stack pointer           = 0x28:0xfffffe010f85c720
frame pointer           = 0x28:0xfffffe000215de00
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 12 (swi4: clock (0))
trap number             = 12
panic: page fault
cpuid = 1
KDB: stack backtrace:
#0 0xffffffff80b4d6e7 at kdb_backtrace+0x67
#1 0xffffffff80b068e7 at vpanic+0x177
#2 0xffffffff80b06763 at panic+0x43
#3 0xffffffff80f8939f at trap_fatal+0x35f
#4 0xffffffff80f893f9 at trap_pfault+0x49
#5 0xffffffff80f88a9c at trap+0x29c
#6 0xffffffff80f68f6c at calltrap+0x8
Uptime: 47d3h46m30s

In passing it's interesting to note that the stack backtrace is as good as useless: the functions are all called as a result of the problem. To find the real cause you need to dig deeper:

=== kgdb -> bt
#0  doadump (textdump=) at pcpu.h:230
#1  0xffffffff80b064fb in kern_reboot (howto=260)
    at /eureka/home/src/FreeBSD/svn/stable/11/sys/kern/kern_shutdown.c:383
#2  0xffffffff80b06921 in vpanic (fmt=, ap=)
    at /eureka/home/src/FreeBSD/svn/stable/11/sys/kern/kern_shutdown.c:776
#3  0xffffffff80b06763 in panic (fmt=)
    at /eureka/home/src/FreeBSD/svn/stable/11/sys/kern/kern_shutdown.c:707
#4  0xffffffff80f8939f in trap_fatal (frame=0xfffffe010f85c660, eva=0)
    at /eureka/home/src/FreeBSD/svn/stable/11/sys/amd64/amd64/trap.c:904
#5  0xffffffff80f893f9 in trap_pfault (frame=0xfffffe010f85c660, usermode=0) at pcpu.h:230
#6  0xffffffff80f88a9c in trap (frame=0xfffffe010f85c660)
    at /eureka/home/src/FreeBSD/svn/stable/11/sys/amd64/amd64/trap.c:438
#7  0xffffffff80f68f6c in calltrap () at /eureka/home/src/FreeBSD/svn/stable/11/sys/amd64/amd64/exception.S:231
#8  0xffffffff829d83a4 in _nv008794rm () from /boot/modules/nvidia.ko
#9  0x0000000000000001 in ?? ()
#10 0xffffffff829d83b9 in _nv008790rm () from /boot/modules/nvidia.ko
#11 0xfffff800852e9b80 in ?? ()
#12 0xffffffff829d8237 in _nv008791rm () from /boot/modules/nvidia.ko
#13 0xfffffe000215de00 in ?? ()
#14 0xfffffe000215de78 in ?? ()
#15 0x0000000000000000 in ?? ()

nvidia.ko! For which, of course, we have no source. Should I even bother to report it to Nvidia? They'll just ask me to install the latest version of the driver and try again, I fear. But for some time I've been pondering the Radeon card that I got a few months ago and which worked out of the box. A far cry from Nvidia: teevee is down-rev because the latest version didn't work well with my hardware.

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. 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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