Not 2 weeks ago, but years ago I turned my whole living room into a pinhole camera by covering the whole window with cardboard, made a small hole through it that would project a huge (I think it was upside-down) image on the wall at the opposite side of the room, thought the result was quite impressive.
It has to be upside down. Light travels in straight line. Top of the image goes to pinhole and continues to the bottom of projected image. And vice versa.
However, here is philosofical question. Image flips, but at certain point, it has to be infinitely small. How come all those photons/waves do not mix and interfere with each other and create mess in the center of the lens.
However, here is philosofical question. Image flips, but at certain point, it has to be infinitely small. How come all those photons/waves do not mix and interfere with each other and create mess in the center of the lens.
Later M cameras don’t require cutting the film.
Cool - I wasn’t aware of the LSST project. I suppose 288Mpix is a “crop” of 3200Mpix, but sort of depends on compared to which format?
The RST has a 2300mm dia objective and is an F/7.9 aperture - making it an 18,000mm focal length lens. Plus, it’s mounted on the ultimate steady-cam active gimbal for a 4000kg mass camera. It’s kind of funny to say I have an 18,000mm lens in my 288Mpix camera.
Kiev, in former USSR had some nice camera and lens factories. I’m not sure if they continued after the breakup. There are some nice Kiev 4A’s that can be had for a song on eBay. With 53mm Jupiter F/2 lens for under $200 tested and fully working. Actually a very wide rangefinder base - should be quite accurate focusing if properly calibrated. The Jupiter 8M lens is a copy of a Zeiss Sonnar I think.
The 4A’s are made from same tooling as Contax but relocated to Kiev. They take great pictures too from what I have seen on the reviews.
The 4A’s are made from same tooling as Contax but relocated to Kiev. They take great pictures too from what I have seen on the reviews.
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I can add one more philosophical question: the image on the eye's retina is also "upside down". So is the camera obscura (pinhole camera) image upright then?
These are the other two Pentax lenses I have. The one on the left is a bit plasticky, and is a DSLR auto focus lens but the 50mm 1.7 on the right (I thought it was a 55mm 1.4 or 1.6 when I mentioned it while travelling last week) is a film SLR k-mount so works with my modern DSLR with a bit of cropping - it is a fantastic lens. Very heavy, all metal construction manual focus. I bought it in Japan at the height of the DSLR boom in 2008/9 for pennies. They’re probably a bit dearer now - it got some good feedback on Pentax Forums.
The inversion happens from geometry and not because the rays are going through an infinitely small spot and flipping.
The top ray from left to right goes in parallel and focuses down to a spot per focal length, middle ray goes through lens center and hence does experience refraction. Bottom ray is the inverse of top ray and goes through at angle to be refracted parallel to axis. These three converge at the focal spot on image plane and we can see Y1 becomes upside down Y2. It’s pure geometry and no focusing to an infinite spot is happening here to cause the flipping. Below is same diagram as human eye but image plane is a spherical retina.
I think you might be referring to what happens inside a Keplerian telescope, where there is an intermediate image plane. But that’s not like a single spot where ALL the rays go through as there are an infinite bundle of rays which pass through and then collimated to be then imaged onto the retina by an eyeball.
Keplerian telescope:
Btw, when we focus intense laser light to a spot using a lens, the electric field can sometimes be high enough to induce non linear effects and the light waves indeed mix and produce 2nd, 3rd harmonics etc or difference frequency mixing. This you can generate blue light from red light or UV light from blue light, or green light from infrared light. Crazy stuff.
Green laser pointers use 1.06um light from a Nd:YAG laser pumped by 800nm diode laser. The 1.06um light is frequency doubled to green 532nm light by a small KDP crystal. All this in a $5 laser pointer.
Sometimes a high pressure has cell is used exactly for this purpose or a non linear crystal like KDP, ADP, BBO, etc.
Potassium Dihydrogen Phospate (KDP)
Ammonium Dihydrogen Phosphate (ADP)
Beta Barium Fluorate (BBO)
The top ray from left to right goes in parallel and focuses down to a spot per focal length, middle ray goes through lens center and hence does experience refraction. Bottom ray is the inverse of top ray and goes through at angle to be refracted parallel to axis. These three converge at the focal spot on image plane and we can see Y1 becomes upside down Y2. It’s pure geometry and no focusing to an infinite spot is happening here to cause the flipping. Below is same diagram as human eye but image plane is a spherical retina.
I think you might be referring to what happens inside a Keplerian telescope, where there is an intermediate image plane. But that’s not like a single spot where ALL the rays go through as there are an infinite bundle of rays which pass through and then collimated to be then imaged onto the retina by an eyeball.
Keplerian telescope:
Btw, when we focus intense laser light to a spot using a lens, the electric field can sometimes be high enough to induce non linear effects and the light waves indeed mix and produce 2nd, 3rd harmonics etc or difference frequency mixing. This you can generate blue light from red light or UV light from blue light, or green light from infrared light. Crazy stuff.
Green laser pointers use 1.06um light from a Nd:YAG laser pumped by 800nm diode laser. The 1.06um light is frequency doubled to green 532nm light by a small KDP crystal. All this in a $5 laser pointer.
Sometimes a high pressure has cell is used exactly for this purpose or a non linear crystal like KDP, ADP, BBO, etc.
Potassium Dihydrogen Phospate (KDP)
Ammonium Dihydrogen Phosphate (ADP)
Beta Barium Fluorate (BBO)
OK, camera people, can anyone please tell me why is it that my Olympus C-8080 produces images just as I see them (as with the naked eye), whilst my Olympus OMD-EM5 (which seems to be of a higher spec) does not, it produces "Camera pictures". I much prefer the C-8080.
(I have a 14mm to 42mm and 40mm to 150mm zooms for the OMD).
Many thanks.
(I have a 14mm to 42mm and 40mm to 150mm zooms for the OMD).
Many thanks.
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The 8080 has a 2/3rd in format Sony CCD technology sensor. The EM5 has a micro 4/3 format sensor with MOS technology.
There might be some signal processing differences. But CCD sensors, in my experience, are generally lower noise and more pleasing and film-like. I have an old Canon 4MP point and shoot and its images were excellent in tonal and color rendition although lower resolution.
Maybe just us old fogeys saying “they just don’t make them like they used to” mentality?
There might be some signal processing differences. But CCD sensors, in my experience, are generally lower noise and more pleasing and film-like. I have an old Canon 4MP point and shoot and its images were excellent in tonal and color rendition although lower resolution.
Maybe just us old fogeys saying “they just don’t make them like they used to” mentality?
Beautiful cat. Is she an Abysinian?
Here is my cat shot on 50mm F/1.1 wide open. ISO800 1/320sec. She is sort of in a good mood.
I was walking around with my new manual focus 25mm F/2 lens today on my GX1. Full frame equivalent of 50mm but deeper depth of field of a 25mm lens. It has a hyper focal scale on top. Gosh, I really missed that from my old manual focus Nikon. Wonderful to set it at F/8, set to hyper focal 0.9m to infinity and you can go about shooting very quickly. There is no waiting for the lens to focus and the there is no focus motor noise. The shutter release is instantaneous - as soon it is depressed. Everything is in focus - always. Daylight and ISO200 or 400 is adequate for F/8 and pretty quick shutter speeds to prevent blur. It’s very refreshing compared to the autofocus lens.
Here is the lens setting. Set it and forget it! I am going to do a lot more of this and can see how street photography works now given there is no delay or need to focus. Just compose, wait for the “decisive moment”, and shoot.
Here is the lens setting. Set it and forget it! I am going to do a lot more of this and can see how street photography works now given there is no delay or need to focus. Just compose, wait for the “decisive moment”, and shoot.
