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#41
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Let's Photograph Comet 46P Wirtanen
On Mon, 24 Dec 2018 22:54:55 -0600, hleopold
wrote: On Dec 24, 2018, Paul Schlyter wrote (in et): On Sun, 23 Dec 2018 18:30:49 -0600, wrote: Way back in the late 70s early 80s I did, for a while, try photography with my scopes, but otherwise I have been strictly a visual observer. I cant believe the great stuff that we have these days. I am not really a fan of digital photography in many ways, I loved shooting film, and that was how I did astro photos back then. You can still shoot film if that's what you enjoy to do. The camera stores near me hardly carry any film anymore, except for 4x5 or 8x10. And I have gotten out of the habits I used to have. I love my smart phone for its ability to grab shots that pop up unexpectedly. The camera in your smart phone is a digital camera so that makes you a fan of digital photography. The digital cameras are more than just DSLR cameras where a digital sensor has replaced the film. Almost all digital cameras now also has video capability. There are really small "adventure cameras" you can bring along in conditions where you wouldn't bring your regular camera. There are surround cameras which photograph in every possible direction all over the 55000 square degrees over the entire sphere around the camera. Some sky watchers set upp all-sky cameras (which photograph only half the sphere) and run them all night long every night and examine the time-lapse movies afterwards. A lot of this would hardly have been possible with older film cameras. |
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Let's Photograph Comet 46P Wirtanen
On Mon, 24 Dec 2018 22:04:24 -0600, hleopold
wrote: If the numerator is always 20, what does this 20 mean? Is 20/20 in some way different from, say, 25/25 or.30/30? As I understand it, you should be able to see at 20 feet as the average person would see at 20 feet. (An average person with good eyesight of course.) If you are shown to have a 20/30 in your right eye it means that you see at 20 feet is like that average person would see at 30. In other words, your eyesight is not that great. But what's the point of always having 20 as the numerator? Why not instead perform the division and say 0.67 instead of 20/30? Or, if you prefer common fractions, 2\3? After all 2/3 is equal to 20/30. |
#43
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Let's Photograph Comet 46P Wirtanen
On Mon, 24 Dec 2018 14:47:15 -0700, Chris L Peterson
wrote: On Mon, 24 Dec 2018 22:33:39 +0100, Paul Schlyter wrote: On Mon, 24 Dec 2018 09:26:32 -0500, Davoud wrote: 20/20, or metric 6/6 = 1. It's explained at https://en.wikipedia.org/wiki/Visual_acuity#Measurement. Ok, so it measures the visual acuity at a distance of 20 feet. But wouldn't a measure of (practically) infinite distance be more interesting to skywatchers? No stars are only 20 feet away. The distance is largely irrelevant. It's measuring resolution... the ability to detect close high contrast features as separate from one another. The distance of 20 feet is simply a standard so that the test chart is always the same, and it's a distance that is practical in a typical testing situation. Optically, 20 feet is pretty much the same as infinity for the human eye in terms of accommodation. Modern refraction techniques project patterns on the back of the eye and directly assess accommodation, focus, and astigmatism. But this is usually translated to the 20:X notation for simplicity. But if the distance is irrelevant, why not perform the division and say 0.67 instead of 20/30? Or at least 2/3 instead of 20/30? After all it means that the person with 20/30 eyesight has 2/3 or 0.67 of normal visual acuity. |
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Let's Photograph Comet 46P Wirtanen
On Tue, 25 Dec 2018 10:46:25 +0100, Paul Schlyter
wrote: But if the distance is irrelevant, why not perform the division and say 0.67 instead of 20/30? Or at least 2/3 instead of 20/30? After all it means that the person with 20/30 eyesight has 2/3 or 0.67 of normal visual acuity. It's just convention. |
#45
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Let's Photograph Comet 46P Wirtanen
On Tue, 25 Dec 2018 07:33:29 -0700, Chris L Peterson
wrote: On Tue, 25 Dec 2018 10:46:25 +0100, Paul Schlyter wrote: But if the distance is irrelevant, why not perform the division and say 0.67 instead of 20/30? Or at least 2/3 instead of 20/30? After all it means that the person with 20/30 eyesight has 2/3 or 0.67 of normal visual acuity. It's just convention. An unnecessary convention which should be removed. Suppose that I, instead of saying "it's 5 degrees outside", suppose I would say "it's 35/7 degrees outside". It's the same thing, but you'd probably ask why I involved that 7 in the temperature, and then I would reply "it's just convention"... See? |
#46
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Let's Photograph Comet 46P Wirtanen
On Dec 25, 2018, Paul Schlyter wrote
(in et): On Mon, 24 Dec 2018 22:04:24 -0600, wrote: If the numerator is always 20, what does this 20 mean? Is 20/20 in some way different from, say, 25/25 or.30/30? As I understand it, you should be able to see at 20 feet as the average person would see at 20 feet. (An average person with good eyesight of course.) If you are shown to have a 20/30 in your right eye it means that you see at 20 feet is like that average person would see at 30. In other words, your eyesight is not that great. But what's the point of always having 20 as the numerator? Why not instead perform the division and say 0.67 instead of 20/30? Or, if you prefer common fractions, 2\3? After all 2/3 is equal to 20/30. I haven’t a clue. All I can say is that maybe your local eye doctor might have an answer. The only thing I can think of is that like any other part of human life eye doctors stick with some traditions. Nearly every organization has traditions that are slow to change. As a former Navy person I ran into lots of old traditions while in. Many did not really make any sense, now. Maybe they did way back when. As a long time printer we had lots of traditions on how we measured things, and even in the last ten years many of those have slowly fallen to the wayside with the spread of digital printing. We used to have many terms that were in use daily by printers back in 1969 when I first got into the business. When I reentered it about 32 years ago most were still in daily use. But by the time I was retired a couple of years ago most new printers had never heard of them even if they had been working as printers for 10 years or so. The guy that trained me on the big web presses was always mentioning things that we never dealt with anymore. And of course when I started as a printer I started on one tower flat bed/flat sheet presses before much later moving on to web multi-tower presses, again, a very different kind of printing. Printing used to be as they used to say: more art than science, same goes for making eyeglasses. But these days not only are presses being replaced by digital (laser) printers so are set up and pre-press, most of it is now done by computers, as is mixing of inks (if you are still using a press that actually using printers ink instead of pre-mixed cartridges from the manufacture.) Kerning, that used to be one of the most important parts of printing pages of print, and one source of many traditions of how printers measure and move things. Now nearly all of that is dealt with automatically by the software long before the image ever leaves the set up computers. This was something that I seldom had to deal with as I was an offset printer, not a linotype printer. I have had some conversations with lino printers that have left both of us scratching our heads even though the presses we both used are (almost) identical, only the method is placing ink on paper is (vastly) different. Both types of printing have very different current styles of training. Lino is even further along towards being obsolete than off-set printing. These days both types are becoming strictly boutique print shop use. Boutique Print Shop, three words I never thought I would ever use in a sentence. It used to be that a printer had to worry about things like what was the temp and humidity at the time you were printing, and just for fun add in just how old is that paper you are printing on. Paper that is less then six months old prints very differently than a roll that is six years old and what kind of paper, how thick, coated or uncoated, AND how had it been stored during that time. Most of the time nobody could tell you this kind of stuff, so you had to learn by doing and by listening to older printers. This was one reason most old printers did not really like training people who had gone through a tech school, they had a lot of book training but very little practical training. Now most of what we trained for is built into the software and hardware, or completely ignored since the folks that build them expect the users to actually use high quality paper, ink and not run them for 24 hours straight or longer and never, ever cut corners. Things like how much, or little fountain solution to use aren’t even a part of laser printed jobs. Or that sometimes you need to add a little alcohol to that solution to fix a toning problem that just won’t go away no matter what the makers of the machine say. The guy that trained me on my last press just retired, the press he had used for most of his career was almost identical to the one he trained me on, but the type of printing he did before coming to our shop was very different, instead of one roll of paper going through the entire press, getting different inks printed by anywhere from four to ten different printing towers, he started off printing the old multi layered, multi-colored forms.What we used to call business forms. So his press that he learned on had up to six rolls of (basically) tissue paper being fed into different towers to be printed, collated into a single form, then it would be cut, glued into whatever form the customer needed. Collectively these were known as “business forms,” they came in hundreds of weird and wonderful forms, colors and styles. Having heard the tales that I was told by my trainer, I am glad I missed that particular form of torture. His favorite tale dealt with splicing tissue paper back together ten or twelve feet in the air standing on top of the press or on a ladder using one hand, the other was to prevent him from falling into the press. Now years ago I had actually been to his former employer, I saw the presses he worked on, in function they operated exactly as the one he trained me on, but the reality was just as awful as he described, far worse really. Rolls of paper being fed into the press at each tower, paper running above the press from each tower before diving back into it to be collated and folded by the bindery unit, I would have believed him if he said he had to do the splicing while hanging by his toes doing a Tarzan scream. I was only there to pick up some forms for my then employer, thank Bes. Too bad the family that owned the company sold it, only to have it closed a year later. But I got a great trainer out of it and a good friend. Sorry about all that, but it is late at night and I am bored at the moment and I guess I have the holiday blues. Why am I suddenly reminded of the old detective from The Streets of San Francisco? I am not that bad, really. -- Harry F. Leopold The Prints of Darkness (remove gene to email) "The line separating painfully bad analogies from weirdly good ones is as thin as a soup made from the shadow of a chicken that was starved to death." - Alydar2 |
#47
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Let's Photograph Comet 46P Wirtanen
On Dec 25, 2018, Paul Schlyter wrote
(in t): On Mon, 24 Dec 2018 22:54:55 -0600, wrote: On Dec 24, 2018, Paul Schlyter wrote (in et): On Sun, 23 Dec 2018 18:30:49 -0600, wrote: Way back in the late 70s early 80s I did, for a while, try photography with my scopes, but otherwise I have been strictly a visual observer. I cant believe the great stuff that we have these days. I am not really a fan of digital photography in many ways, I loved shooting film, and that was how I did astro photos back then. You can still shoot film if that's what you enjoy to do. The camera stores near me hardly carry any film anymore, except for 4x5 or 8x10. And I have gotten out of the habits I used to have. I love my smart phone for its ability to grab shots that pop up unexpectedly. The camera in your smart phone is a digital camera so that makes you a fan of digital photography. Because it is at hand at all times. This I find a very good thing. But, like the audio guys will argue about tube versus digital amps, the old stuff “feels” better, or looks better. It is emotional, I know that. When I pulled that old range-finder camera out with that large chunk of glass on it I knew exactly what it would do from lots and lots of practice. I knew how to manipulate the controls to get just the sort of shot I wanted. With digital cameras you have to deal with some other persons decisions that are built into the software and sometimes those decisions are so burned in you can’t get around them. And, to be honest, shooting a dark street scene I could adjust things to get what I wanted, which is a dark street scene with real blacks, saturated color where there is color. I have never been able to do anywhere as well with digital, it feels “flatter,” grayer instead of real blacks. It is all about the feels, emotions. I always found film, B&W or color negative seemed to work with me. Daylight shots, digital is fine, but for emotional “color” I love film and long shutter times, huge depth of field, dark but not gloomy. “Bright Blackness” is an oxymoron but it works, for me. One of my favorite shots was taken at about 3 in the morning in SF, from the top of a hill looking down a long street towards the bay, shortly after a light rain, a dinner in the left distance with night owls having something to eat before handing home, the dark streets glimmering from distant lights reflecting from the water still on them, and a couple walking to their car, crossing the street. This shot had the lens open for 6 full seconds, basically hand-held, I had plastered myself against a brick wall not breathing, braced myself as well as I possibly could as I counted the seconds until I could close the shutter. I took that shot 10 times that night, one came out perfect, in my opinion. The print was mostly black, little dots of white, red, green and blue reflections off the wet streets and the people that could be seen inside of the dinner and that couple, somewhat blurred, but to me it said that they were in love and I think it came through. Even the cat that sat there watching me make a fool out of myself remained quiet while I got that shot. (No, the cat was not in the shot. He would have been far too close and too bright, it would have been the center of attention, not the couple in the distance.) No, I was not trying to reproduce The Night Owls dinner painting though it is a favorite of mine. It’s all about the feels, man. ;-) Oh, and about that video capability, I don’t do video, never have. It just doesn’t feel right for me, more power to those that enjoy doing it. I like trying to catch humanity in a moment, I may fail often but every once in a while I would luck out, through practice and stubbornness, and get a good shot that says what I want it to say. Which, strangely enough, is in the middle of the night on near empty streets or beaches, sometimes after a light rain. But mostly I want that photo to speak to me, not so much for me. If it says something to me, I got it right, and I am happy. Oh yes, I know I could have carried a tripod with me, but I liked having to work for a shot without having to have half of an studio in a car. I wanted something that did not scream “guy carrying a lot of expensive equipment around in the dark.” Sometimes I carried a mono-pod, this had the advantage of being useful in any number of ways, including being handy as a walking stick if there were a lot of hills and SF had a lot of steep hills. I think I went about photo equipment like I did with bicycling or camping, I liked to keep it light and easy to carry anywhere, so I pretty much stuck with a total of three lens on three cameras, Most times I carried two camera bodies, all three lens, a mono-pod, a light meter and film, lots of film, a roll or two of HP-5 or Tri-X, and three or four rolls of a good, fairly fast color negative film. Maybe a roll of a slow ASA B&W film if I was going to be out until dawn, I enjoyed taking shots of dew-covered flowers in the early light. Oh yes, spare batteries for the light meter, just in case. I did learn my lesson on that subject. The nice thing about this setup is that it didn’t take up a lot of room in my locker on my ship. On a Navy ship space is precious, you never have enough that you actually can control. This is why I never got into developing color film, took up too much room for the chemicals and equipment. I could develop my B&W stuff, but I had them printed elsewhere. A good camera shop with a really good print tech was a friend worth developing a friendship with, they get to know what you shoot and how you like them to look and will actually listen to you if you let them know you have made a change. You always remember them at Christmas and their birthdays. Finding a print tech that likes a challenge isn’t, or wasn’t, that hard back then. I am pretty sure those are getting much harder to find these days. The digital cameras are more than just DSLR cameras where a digital sensor has replaced the film. Almost all digital cameras now also has video capability. There are really small "adventure cameras" you can bring along in conditions where you wouldn't bring your regular camera. There are surround cameras which photograph in every possible direction all over the 55000 square degrees over the entire sphere around the camera. Some sky watchers set upp all-sky cameras (which photograph only half the sphere) and run them all night long every night and examine the time-lapse movies afterwards. A lot of this would hardly have been possible with older film cameras. But those are not the photos I was taking. (Gee, for some reason that line sounds a bit overly familiar. ;-) -- Harry F. Leopold aa #2076 AA/Vet #4 The Prints of Darkness (remove gene to email) “When I am stupid, that is when I am STRONG“ - Codebreaker |
#48
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Let's Photograph Comet 46P Wirtanen
On Wed, 26 Dec 2018 07:48:43 +0100, Paul Schlyter
wrote: On Tue, 25 Dec 2018 07:33:29 -0700, Chris L Peterson wrote: On Tue, 25 Dec 2018 10:46:25 +0100, Paul Schlyter wrote: But if the distance is irrelevant, why not perform the division and say 0.67 instead of 20/30? Or at least 2/3 instead of 20/30? After all it means that the person with 20/30 eyesight has 2/3 or 0.67 of normal visual acuity. It's just convention. An unnecessary convention which should be removed. Fine, take it up with the ophthalmological community. But it works, people are comfortable with it, and I don't imagine it's likely to change. Suppose that I, instead of saying "it's 5 degrees outside", suppose I would say "it's 35/7 degrees outside". It's the same thing, but you'd probably ask why I involved that 7 in the temperature, and then I would reply "it's just convention"... See? If it were convention, it would sound normal to us and we'd use it comfortably. That's pretty much what "convention" means. |
#49
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Let's Photograph Comet 46P Wirtanen
Paul Schlyter:
But if the distance is irrelevant, why not perform the division and say 0.67 instead of 20/30? Or at least 2/3 instead of 20/30? After all it means that the person with 20/30 eyesight has 2/3 or 0.67 of normal visual acuity. Chris L Peterson: It's just convention. Paul Schlyter: An unnecessary convention which should be removed. Suppose that I, instead of saying "it's 5 degrees outside", suppose I would say "it's 35/7 degrees outside". It's the same thing, but you'd probably ask why I involved that 7 in the temperature, and then I would reply "it's just convention"... See? Settle down! What happened? Father Christmas pass you by? Once you know, as Mr. Peterson said, it's a convention, that's all you need to know. It is used over practically the whole world and it works. The world of measurement is full of conventions that, if being originated today, might be done differently. But there is no need to change them when everyone knows them. It explains why the general public uses the English System of measures in the U.S. and some other countriesincluding the U.K., frequentlyits a convention that serves its purpose! I was watching a British cooking show on TV the other day. "Add 250 g of this or that, 500 g of the other and another 200 ml of milk. Roll it up until it looks like this and cut into two-inch sections. Works. -- I agree with almost everything that you have said and almost everything that you will say in your entire life. usenet *at* davidillig dawt cawm |
#50
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Let's Photograph Comet 46P Wirtanen
On Wed, 26 Dec 2018 02:39:53 -0600, hleopold
wrote: On Dec 25, 2018, Paul Schlyter wrote (in et): On Mon, 24 Dec 2018 22:04:24 -0600, wrote: If the numerator is always 20, what does this 20 mean? Is 20/20 in some way different from, say, 25/25 or.30/30? As I understand it, you should be able to see at 20 feet as the average person would see at 20 feet. (An average person with good eyesight of course.) If you are shown to have a 20/30 in your right eye it means that you see at 20 feet is like that average person would see at 30. In other words, your eyesight is not that great. But what's the point of always having 20 as the numerator? Why not instead perform the division and say 0.67 instead of 20/30? Or, if you prefer common fractions, 2\3? After all 2/3 is equal to 20/30. I havent a clue. All I can say is that maybe your local eye doctor might have an answer. No he wouldn't. My local eye doctor wouldn't even say 20/30, she would say 0.67 perhaps rounding it to 0.7 - as would most European eye doctors. The 20/xx stuff is an American idiosyncracy. |
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