Svarichevsky Mikhail - RSS feed http://3.14.by/ Svarichevsky Mikhail - RSS feed en-us Tue, 10 Jun 2006 04:00:00 GMT Mon, 18 Dec 17 09:52:23 +0300 3@14.by 120 10 <![CDATA[PaperBack - proper way of storing information on paper]]> http://3.14.by/en/read/paperback-paper-backup-timecapsule PaperBack made by Oleh Yuschuk.

While playing with it I was able to store ~500 KiB of data on a single side of A4, which could already have some practical use. This density is achieved at 300dpi data density, 80% dot scale (recommended value of 70% gave higher error rate) and 20% for ECC correction. For reliable recovery scanned image had to be slightly sharpened using Gimp2/unsharp mask, but it feels like this is the limit (ECC had to recover ~10% of errors). On 200/240dpi data density everything is much more reliable.

One can for example take a photo of the sheet using film camera and get data microfilms at home ))) Also, this data is easy to read even in distant future and does not depend on spefic reading hardware, so even aliens or humans 1000 years in the future who find a timecapsure with it would be able to read it...

Here is how data looks at 80dpi:


Closer:


Now data at 300dpi, maximum for 600dpi printer:


Even closer (square side is 2.97ΠΌΠΌ). One can see that using less than 2*2 pixels for 1 bit of data would require different recovery approach due to very high rate of errors which will be pattern-dependent. Paper fibers would also cause some issues as higher data densities.

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Mon, 18 Dec 17 00:19:42 +0300
<![CDATA[Olympus UPlanApo 10x0.4 WI - ultimate fun microscope lens]]> http://3.14.by/en/read/Olympus-UPlanApo-10x0.4-WI-water-immersion
Apparently I am a fan of water immersion. Last time when I've got 10x0.3WI lens I thought I am set for life. But recently I've spotted even more interesting lens on ebay: Olympus UPlanApo 10x0.4 WI. That would be my first apochromatic microscope lens. It's very large field of view and 0.4 aperture makes it ~1.8x harder to achieve uniform focus over the field comparing to 10x0.3 WI. But the information density is again ~1.8 times higher.

In the center of the frame new lens (on the left) is sharper due to higher aperture (0.4 vs 0.3):


At the edge we can see that lateral chromatic aberations are lower for APO lens (who knew?). Remainng lateral CA is probably caused by microscope's tube lens. I surely correct lateral chromatic aberration in software, but this lens makes it easier and cleaner.
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Mon, 11 Dec 17 03:46:03 +0300
<![CDATA[Sony a7II: Time for Full Frame (and some fake RAW controversy)]]> http://3.14.by/en/read/ff-time-Sony-a7ii-a77ii-a7riii-fake-raw
Finally I've bought my first full-frame digital camera - Sony A7II, on ebay as usual. While everybody were excited about A7RIII - I was quite disappointed: same sensor as in A7RII and still not solved fake RAW issue (it's there for all Sony camera's though). Why it is called fake RAW? Sony cameras has noise reduction algorithm which you cannot disable. It kicks in at long exposures and is applied even in RAW(!!!!), which completely ruins whole idea of RAW files (=direct stream of data from the imaging sensor for further advanced processing). The most obvious effect of this forced "noise reduction" is erasing 2/3 of the stars at the photos of night sky. You can read very detailed research of the problem here and you can also sign petition to Sony to finally fix it.

As my personal punishment to Sony I've decided to skip few camera generations: I will have fun in full frame with A7II for a while, just like 2 years ago I've started to get experience in E-mount with Sony NEX-5, which was ebayed for 110$. Hopefully some day they will release something like A9RII with 60mpix sensor and fixed fake RAW issue - this camera will be worth to buy new :-)

Glad that I did not ever bought full-frame A-mount camera (A900/A99 - it would have wasted much more money after re-sale), and a little bit sad that 3 years ago I've blindly bought Sony A77II instead of some E-mount camera (like a6000) which was already available at the time...

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Sun, 10 Dec 17 07:32:10 +0300
<![CDATA[Slicing ruby like butter]]> http://3.14.by/en/read/Slicing-ruby-like-butter-diamond-saw
Photo cannot show incredible fluorescence of Ruby at 692nm - longest red wavelength, almost infrared... Deepest and most intense red that human eye can see...


Ruby rod has to be glued to glass holder with expoxy/UV glue:


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Mon, 06 Nov 17 06:14:12 +0300
<![CDATA[Blade Runner 2049]]> http://3.14.by/en/read/blade-runner-2049 ]]> Fri, 06 Oct 17 10:58:40 +0300 <![CDATA[Is 16 terabytes Enough For Anyone?]]> http://3.14.by/en/read/ext4-16tb-raid6-resize2fs-64-bit
After routinely adding yet another 4Tb disk to RAID6 array and trying to resize ext4 partition I was puzzled by the message:
root@lbox2:/var$ resize2fs /dev/md1
resize2fs 1.43.4 (31-Jan-2017)
resize2fs: New size too large to be expressed in 32 bits
That was totally unexpected. EXT4 does not support partitions larger than 16Tb? It appeared that it did not up until somewhat recent time. 5 years ago that would have been a brick wall, 2 years ago I would have to wrestle a little with bleeding edge resize2fs/kernel and now it all works on-the-fly out of the box. One just need to convert this ext4 partition to 64-bit format:
root@lbox2:/var$ resize2fs -b /dev/md1
resize2fs 1.43.4 (31-Jan-2017)
Converting the filesystem to 64-bit.
The filesystem on /dev/md1 is now 3907015424 (4k) blocks long.

root@lbox2:/var$ resize2fs /dev/md1
resize2fs 1.43.4 (31-Jan-2017)
Resizing the filesystem on /dev/md1 to 4883769280 (4k) blocks.
The filesystem on /dev/md1 is now 4883769280 (4k) blocks long.

root@lbox2:/var$ mount /var/bigfatdisk

root@lbox2:/var/bigfatdisk$ df . -H
Filesystem      Size  Used Avail Use% Mounted on
/dev/md1         20T   14T  5.9T  71% /var/bigfatdisk

xy@lbox2:~$ cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md1 : active raid6 sdf1[0] sdg1[7] sdh1[6] sdc1[5] sdb1[3] sde1[2] sda1[1]
      19535077120 blocks super 1.2 level 6, 128k chunk, algorithm 2 [7/7] [UUUUUUU]
      bitmap: 1/466 pages [4KB], 4096KB chunk, file: /var/md1_intent.bin

unused devices: <none>



I remember in the late 90's i've been to ftp.cdrom.com - it had enormous 0.5Tb array: it felt like absolutely insane volume of data (I had 850Mb HDD at the time). Probably readers of this article in 2037 would have 1024-layer 3D phase-change memory with 64Tb in 2.5" drive. Good for you, readers from the future... Although it is also possible that popularization of online-content, streaming and cloud apps will make it almost obsolete to have large local storage (with a few exceptions).

BTW since I went for softraid at home about 8 years ago - I had not a single HDD failure (about 50 hdd-years). Still pays off - much less worries about at least 1 thing... ]]>
Tue, 26 Sep 17 23:47:54 +0300
<![CDATA[Golden autumn]]> http://3.14.by/en/read/gold-autumn ]]> Thu, 14 Sep 17 17:18:52 +0300 <![CDATA[Aftermath of X9.3 solar flare]]> http://3.14.by/en/read/solar-minimum-x9-solar-flare ]]> Sun, 10 Sep 17 06:56:47 +0300 <![CDATA[More Deep Space]]> http://3.14.by/en/read/Deep-Space-Andromeda-M110-M15-pleiades body:after {
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Finished processing photos from my last trip so we all can see the results.

Let's start from Milky Way near M6, M7 (exposure 85x3.2s):

M23, M24, M25 - 226x3.2s:


This is closest galaxy to us, Andromeda. One can see it's arms and spiral structure here. 205x3.2s.
Fuzzy spot below it is another galaxy: M110, also known as NGC 205.


Pleiades (88x3.2s):


And this is M15 (314x3.2s) to feel the scale and compare to my 1 hour exposure on 61cm telescope that I did 3 years ago. Here you can barely see a hint for individual stars in the globular cluster. One need much more than 55mm of focal length here:
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Wed, 06 Sep 17 04:49:57 +0300
<![CDATA[Deeper look at the center of our galaxy]]> http://3.14.by/en/read/milky-way-astrophotography-plate-solver body:after {
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This is my first experience in deep sky photography. Best place to start is center of our galaxy - where deep sky objects are densely packed.

128 shots @3.2 seconds exposure each. Sony NEX-5 with Canon FD 55mm F1.2@2.2. All frames were stacked using DeepSkyStacker, plate solving and annotation is done by All Sky Plate Solver. There were 2 shooting sessions for this subject - both at Tenerife mountains, at heights 1500 and 2200 meters. Sky glow was twice brighter at 1500m, so this batch of 106 shots was not used in final stacking. Even at 2200m conditions were far from perfect - wind from Africa carried visible dust which contributed to background brightness.

Next time camera with more modern sensor will help as well as less-bright (!!) lens: F1.2 was making bright stars too large even when stopped down to F2.2. And surely, sky tracking mount will allow much longer exposures and higher image SNR.

On mouse over - annotation. Higher resolution on click.
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Sun, 03 Sep 17 23:17:51 +0300