Year of the Tiger.
Happy New Year. あけましておめでとうございます。
Thursday, December 31, 2009
Wednesday, December 30, 2009
Towards A More Progressive Viewpoint
No, not progressive politics, progressive eyeglasses. I got a pair recently, since I was having real trouble reading small print. Bifocals or reading glasses are one of those inevitable things in life: if you don't need them now, don't worry - you will, eventually. As we age, we all start having trouble focusing close and eventually we will need reading glasses or bifocal glasses to help us. It's called presbyopia, and everybody gets it sooner or later. Up until now I've had only a vague notion of what bifocals and reading glasses actually do.
At the top a lens - our eye, say, or a camera lens - is focusing on an object very far away. The light through a lens bends so that it all comes together at a point1. When that point hits our sensors on the left (whether a piece of film, an electronic camera sensor or our retina) we get a sharp view of the object.
Below we've moved close to the object. The light from it now comes from much steeper angles. But the lens still bends light the same amount as before. The light rays on both sides act like a see-saw, with the lens itself as the center point. So the point of focus moves further away.
We need to change the focus depending on the distance. At the top is how a camera lens does it: the point of focus is behind the sensor, so we move the lens forward until the point of focus is on the sensor again.
The second picture illustrates how our eyes focus. Since the lens isn't bending the light strongly enough, we squish the lens so that it becomes thicker and bends light more. We can do that since our lenses are soft and jelly-like, unlike the glass lenses used in cameras.
Like many, many other people, I'm near-sighted. At the top we see the cause: the retina in the back of the eye sits too far away from the lens. Even when the lens is as flat as possible it still bends light too much to bring far-away things into focus. We can fix this with a convex lens, like the one on the right, that'll effectively weaken our own lens and let us focus far away. Think of it as the curve of the convex lens being subtracted from the curve of our own lens.
Presbyopia is the inability to focus close, and at the bottom we see the reason for it: as we age the lens gradually hardens, and it can no longer thicken enough to bend the light for close objects. The way to fix this is with a convex lens like the one on the right that will help make the eyes stronger. The curve of the concave lens is added to the curve of our own lens, effectively making the combination thicker.
So, with presbyopia you can use a convex lens to get closer focus. Cheap reading glasses sold here and there are exactly that2. This is sufficient for people with otherwise good eyesight.
With nearsightedness you use a concave lens to get infinity focus. Now, here's a problem: what do you do if you're both near-sighted and presbyopic? As you can see in the figure above, the corrective lenses are opposites: one cancels out the other. How do you make a lens that corrects for both at the same time?
Well, you don't. A concave lens for near-sightedness worsens presbyopia - it makes the minimum focusing distance longer - while a convex lens for presbyopia worsens focus at infinity. This is why they're called reading glasses; you can't see far away wearing them so you only use them for close work.
Since glasses for near-sightedness worsens presbyopia, people can get around mild presbyopia simply by removing their glasses or looking below or above the rim when they read; you see this quite often. But once the presbyopia worsens it's no longer enough. People that have astigmatism as well - like me - need glasses at all viewing distances, so removing your glasses doesn't help much.
You could have two pairs of glasses of course, and switch between them. That's a hassle, though, so you'd really like to combine them into one pair. The traditional - and still best - method is simply to "cut out" the lower central part of concave lenses for near-sightedness and replace with convex lenses for presbyopia. That gives you those characteristic half-moon bifocal glasses that people instantly recognize as "old-folks glasses". While they're really the best type of glasses, they're not well liked.
Instead we have progressive glasses, so named because they go smoothly from a nearsighted concave lens toward the top to a convex (or at least less concave) lens at the bottom. This is actually very complicated; you want the change to be gradual, without too much visual bending, blurring or other weird effects during the transformation. We don't look through a point in the glasses, but through a whole area, so a single point in the lens may both be part of the lower edge of the concave near-sighted area toward the top, and part of the convex presbyopic area at the bottom at the same time. Add the astigmatic correction for people like me and the lens surface will get quite complicated.
There's apparently many progressive lens designs, but they are all compromises between conflicting goals. In my case I get far sight in the upper center; near sight in the lower center and towards the edges; and middle sight in a roughly H-shaped area in the very center and along the left and right edges.
One effect that creates problems for some people is that these are lenses, and they don't just move the focus forward or back. Concave lenses make things smaller, and convex lenses make them bigger - magnifying glasses are just strong convex lenses after all. Now, eye-wear lenses are typically fairly weak, but the effect is not negligible. The eyes of near-sighted people tend to look smaller, and the eyes of strongly far-sighted people can look huge behind their glasses.
This also means that the world looks a bit smaller and zoomed out when you wear concave lenses for near-sightedness. And the world looms a bit closer with convex reading lenses. This is normally fine; you quickly get used to it. But with progressive lenses the world gets smaller in some areas of your field of view and larger in other areas, like a funhouse mirror. And as you move around and move your head things shift between these areas to bend, stretch, distort and generally make you feel a little like you're drunk. People normally get used to this - I had no problems - but some people never really adapt. They're better off with bifocal glasses instead.
There are progressive contact lenses, by the way, where you get far vision in the very center and close vision around the edge, but people who've tried them don't seem too impressed. Another way is to wear a contact for far sight on one eye, and close on the other. Me, I'll just rather wear glasses; I've done so for most of my life after all, so this is no problem for me.
--
At the top a lens - our eye, say, or a camera lens - is focusing on an object very far away. The light through a lens bends so that it all comes together at a point1. When that point hits our sensors on the left (whether a piece of film, an electronic camera sensor or our retina) we get a sharp view of the object.
Below we've moved close to the object. The light from it now comes from much steeper angles. But the lens still bends light the same amount as before. The light rays on both sides act like a see-saw, with the lens itself as the center point. So the point of focus moves further away.
We need to change the focus depending on the distance. At the top is how a camera lens does it: the point of focus is behind the sensor, so we move the lens forward until the point of focus is on the sensor again.
The second picture illustrates how our eyes focus. Since the lens isn't bending the light strongly enough, we squish the lens so that it becomes thicker and bends light more. We can do that since our lenses are soft and jelly-like, unlike the glass lenses used in cameras.
Like many, many other people, I'm near-sighted. At the top we see the cause: the retina in the back of the eye sits too far away from the lens. Even when the lens is as flat as possible it still bends light too much to bring far-away things into focus. We can fix this with a convex lens, like the one on the right, that'll effectively weaken our own lens and let us focus far away. Think of it as the curve of the convex lens being subtracted from the curve of our own lens.
Presbyopia is the inability to focus close, and at the bottom we see the reason for it: as we age the lens gradually hardens, and it can no longer thicken enough to bend the light for close objects. The way to fix this is with a convex lens like the one on the right that will help make the eyes stronger. The curve of the concave lens is added to the curve of our own lens, effectively making the combination thicker.
So, with presbyopia you can use a convex lens to get closer focus. Cheap reading glasses sold here and there are exactly that2. This is sufficient for people with otherwise good eyesight.
With nearsightedness you use a concave lens to get infinity focus. Now, here's a problem: what do you do if you're both near-sighted and presbyopic? As you can see in the figure above, the corrective lenses are opposites: one cancels out the other. How do you make a lens that corrects for both at the same time?
Well, you don't. A concave lens for near-sightedness worsens presbyopia - it makes the minimum focusing distance longer - while a convex lens for presbyopia worsens focus at infinity. This is why they're called reading glasses; you can't see far away wearing them so you only use them for close work.
Since glasses for near-sightedness worsens presbyopia, people can get around mild presbyopia simply by removing their glasses or looking below or above the rim when they read; you see this quite often. But once the presbyopia worsens it's no longer enough. People that have astigmatism as well - like me - need glasses at all viewing distances, so removing your glasses doesn't help much.
You could have two pairs of glasses of course, and switch between them. That's a hassle, though, so you'd really like to combine them into one pair. The traditional - and still best - method is simply to "cut out" the lower central part of concave lenses for near-sightedness and replace with convex lenses for presbyopia. That gives you those characteristic half-moon bifocal glasses that people instantly recognize as "old-folks glasses". While they're really the best type of glasses, they're not well liked.
Instead we have progressive glasses, so named because they go smoothly from a nearsighted concave lens toward the top to a convex (or at least less concave) lens at the bottom. This is actually very complicated; you want the change to be gradual, without too much visual bending, blurring or other weird effects during the transformation. We don't look through a point in the glasses, but through a whole area, so a single point in the lens may both be part of the lower edge of the concave near-sighted area toward the top, and part of the convex presbyopic area at the bottom at the same time. Add the astigmatic correction for people like me and the lens surface will get quite complicated.
There's apparently many progressive lens designs, but they are all compromises between conflicting goals. In my case I get far sight in the upper center; near sight in the lower center and towards the edges; and middle sight in a roughly H-shaped area in the very center and along the left and right edges.
One effect that creates problems for some people is that these are lenses, and they don't just move the focus forward or back. Concave lenses make things smaller, and convex lenses make them bigger - magnifying glasses are just strong convex lenses after all. Now, eye-wear lenses are typically fairly weak, but the effect is not negligible. The eyes of near-sighted people tend to look smaller, and the eyes of strongly far-sighted people can look huge behind their glasses.
This also means that the world looks a bit smaller and zoomed out when you wear concave lenses for near-sightedness. And the world looms a bit closer with convex reading lenses. This is normally fine; you quickly get used to it. But with progressive lenses the world gets smaller in some areas of your field of view and larger in other areas, like a funhouse mirror. And as you move around and move your head things shift between these areas to bend, stretch, distort and generally make you feel a little like you're drunk. People normally get used to this - I had no problems - but some people never really adapt. They're better off with bifocal glasses instead.
There are progressive contact lenses, by the way, where you get far vision in the very center and close vision around the edge, but people who've tried them don't seem too impressed. Another way is to wear a contact for far sight on one eye, and close on the other. Me, I'll just rather wear glasses; I've done so for most of my life after all, so this is no problem for me.
--
#1 You have perhaps heard the term "diopter". It's a measure of how strong a lens is, and is really just the inverse of the distance from the lens to the point of focus when you focus on something infinitely far away. So a 1-diopter lens will bring the light together one meter behind the lens. A 2-diopter lens brings it to a point 1/2 meters away; a 10-diopter lens focuses infinity at 1/10 meter - ten centimeters - away and so on.
#2 As an aside, "macro filters" for cameras are the same thing too: an extra lens you screw in front of your ordinary camera lens so you can get closer and get a bigger picture of small things. They're an inexpensive way to play with macro photography.
For SLR cameras, you can also get "extension tubes". They're hollow tubes that fit between the camera and lens and simply move the lens further from the sensor so you focus closer than you normally could.
For SLR cameras, you can also get "extension tubes". They're hollow tubes that fit between the camera and lens and simply move the lens further from the sensor so you focus closer than you normally could.
Monday, December 28, 2009
Back to Work
We're back from Hokkaido. We came home late last night and only did the most pressing things (like putting away all the salmon, squid, sausages and cheeses we've bought) before collapsing in bed.
Today is a work day for me, and tomorrow is the first day of the New Year holidays, which last until monday next week this year. We have a single monday workday before a week off, in other words, and needless to say, the department isn't exactly a buzzing hive of frantic activity today. There's a grand total of three students in the main room, and none of the other postdocs or faculty have yet to show up. Most of them have taken the day off, of course.
Me, I have a poster and a presentation to prepare for next month, and I've yet to finishn the modeling I was hoping to have done by then. So I work today, and I expect to plod away at it over the holiday as well.
I have plenty to do, there's a big pile of pictures to go through, and two rolls of film to develop and scan. Don't expect quick, complete Hokkaido holiday coverage here in other words.
Japanese crane, Hokkaido. Quick train shot.
Today is a work day for me, and tomorrow is the first day of the New Year holidays, which last until monday next week this year. We have a single monday workday before a week off, in other words, and needless to say, the department isn't exactly a buzzing hive of frantic activity today. There's a grand total of three students in the main room, and none of the other postdocs or faculty have yet to show up. Most of them have taken the day off, of course.
Me, I have a poster and a presentation to prepare for next month, and I've yet to finishn the modeling I was hoping to have done by then. So I work today, and I expect to plod away at it over the holiday as well.
I have plenty to do, there's a big pile of pictures to go through, and two rolls of film to develop and scan. Don't expect quick, complete Hokkaido holiday coverage here in other words.
Japanese crane, Hokkaido. Quick train shot.
Friday, December 25, 2009
Interlude
We've arrived in Sapporo after three nights in eastern Hokkaido. Haven't had time to really go through the pictures taken so far, but here's one from when we left for Hokkaido from Osaka:
Mount Fuji.
Here's a handy tip: For various reasons (mostly to do with atmospheric dispersion), shots taken from an airplane tend to look much better when you convert them to black and white.
Mount Fuji.
Here's a handy tip: For various reasons (mostly to do with atmospheric dispersion), shots taken from an airplane tend to look much better when you convert them to black and white.
Thursday, December 24, 2009
Merry Christmas!
We're in Hokkaido for Christmas, where we're relaxing far away from the stresses of city life. We had a sleep in, had a long walk in the snow-covered countryside, I've just returned from a long soak in the hostel's hot spring bath, and with any luck we'll be stuffed to the gills with sushi and beer by tonight. And just so you see what we're leaving behind:
Crowds gather along Shinsaibashi shopping street to celebrate the true meaning of Christmas. Go ahead, click on the image; it looks much better large.
Huge Friendly Duck says Merry Christmas!
Crowds gather along Shinsaibashi shopping street to celebrate the true meaning of Christmas. Go ahead, click on the image; it looks much better large.
Huge Friendly Duck says Merry Christmas!
Monday, December 21, 2009
Huge, Friendly Duck Is Back (And We're Leaving (but only temporarily))
The Huge rubber duck that floated by Nakanoshima island in Osaka this summer is back! There's a winter light festival happening along Nakanoshima southern beach, from the western end up to the City Hall, and the enormous rubber duck is also back for a repeat appearance. Which makes me inexplicably happy. The festival is apparently up until the 25th, so if you happen to be in Osaka, there's still a chance to go see it.
It's my favourite humongous friendly rubber duck, really. Surprisingly difficult to photograph, though. By the way, if you happen to go here, there's a really good, inexpensive Indian restaurant in the basement of the building just next to the duck. You can take the stairs from the riverside right to the back entrance.
In other news, we're leaving for our winter holiday in Hokkaido tomorrow morning. Which partly explains my relative silence here - I've been trying to finish up some stuff before we leave. We're going to Akan national park again, then to Sapporo for a couple of nights. It should be a lot of fun; I've been looking forward to this all autumn.
The trees along Nakanoshima are decorated, and there's some hot food stalls and things like that as well. Dress warm; the wind along the river is freezing.
There's some Christmas-themed displays as well. We only got this far before the cold got the better of us, so I don't really know what it looks like towards the City Hall.
One guy brought his parrot for a photo shoot. He had a padded cage and only brought it out for a minute or so. My guess is, he's making a New Year's card.
It's my favourite humongous friendly rubber duck, really. Surprisingly difficult to photograph, though. By the way, if you happen to go here, there's a really good, inexpensive Indian restaurant in the basement of the building just next to the duck. You can take the stairs from the riverside right to the back entrance.
In other news, we're leaving for our winter holiday in Hokkaido tomorrow morning. Which partly explains my relative silence here - I've been trying to finish up some stuff before we leave. We're going to Akan national park again, then to Sapporo for a couple of nights. It should be a lot of fun; I've been looking forward to this all autumn.
The trees along Nakanoshima are decorated, and there's some hot food stalls and things like that as well. Dress warm; the wind along the river is freezing.
There's some Christmas-themed displays as well. We only got this far before the cold got the better of us, so I don't really know what it looks like towards the City Hall.
One guy brought his parrot for a photo shoot. He had a padded cage and only brought it out for a minute or so. My guess is, he's making a New Year's card.
Wednesday, December 16, 2009
An Apple A Day
Ritsuko has plenty of friends and acquaintances spread out all over Japan. There's a stronger tradition of gift-giving here than I'm used to; it's not just for celebrations or holidays, but you send stuff to each other now and again for no particular reason. One friend of Ritsuko's (a friend of her fathers, originally) lives and works in Aomori; visiting him was one reason we went there in August last year. Aomori is famous for good tuna, depressed economy and great apples. So, last week, we got a box full of them (apples, not economies):
An apple a day - that's 32 days, half green, half red. And they're big enough that one is plenty for both us to share.
Time to look up some new apple recipes, methinks. We've gotten a box every year for the past few years, and while they're really, really good - juicy and tender and with a perfect balance of sweetness and tartness - they are big and there's quite a lot of them. I sometimes fry them: peel and slice, sprinkle some sugar and cinnamon on both sides and fry in a pan until they start to brown. Eat with ice cream. This year I'd like to try making a real apple pie, though; if anybody has a good recipe (with ingredients easy to find in Japan) I'm all ears.
Aomori, by the way, will get a direct Shinkansen connection late next year. At 320km/h it'll eventually cover Tokyo-Aomori in about three hours, faster and more convenient than flying once you consider the airport travel time, check-in, baggage claim and so on. I really like the Shinkansen. You go straight from one city center to the other without having to transfer or wait in some nondescript departure hall. And with comfortable seats, lots of legroom, little noise and on-board internet I'd prefer it over flying any way.
We could leave Osaka in the morning; have a leisurely lunch and some window shopping in Tokyo; then leave for Aomori in the afternoon, with plenty of time to check in at the hotel and have an appetite-building stroll along the waterfront before dinner. Next year.
An apple a day - that's 32 days, half green, half red. And they're big enough that one is plenty for both us to share.
Time to look up some new apple recipes, methinks. We've gotten a box every year for the past few years, and while they're really, really good - juicy and tender and with a perfect balance of sweetness and tartness - they are big and there's quite a lot of them. I sometimes fry them: peel and slice, sprinkle some sugar and cinnamon on both sides and fry in a pan until they start to brown. Eat with ice cream. This year I'd like to try making a real apple pie, though; if anybody has a good recipe (with ingredients easy to find in Japan) I'm all ears.
Aomori, by the way, will get a direct Shinkansen connection late next year. At 320km/h it'll eventually cover Tokyo-Aomori in about three hours, faster and more convenient than flying once you consider the airport travel time, check-in, baggage claim and so on. I really like the Shinkansen. You go straight from one city center to the other without having to transfer or wait in some nondescript departure hall. And with comfortable seats, lots of legroom, little noise and on-board internet I'd prefer it over flying any way.
We could leave Osaka in the morning; have a leisurely lunch and some window shopping in Tokyo; then leave for Aomori in the afternoon, with plenty of time to check in at the hotel and have an appetite-building stroll along the waterfront before dinner. Next year.
Subscribe to:
Posts (Atom)