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01/05/2005 12:20:28 AM · #1 |
Hello.
I was just looking at the specifications for the Sigma 12-24 and Canon 10-22 on BH. It says that the Sigma has a 122 degree FOV at its widest and the Canon as 107. How is that possible? Is that wrong?
June
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01/05/2005 12:28:51 AM · #2 |
| The Canon is one of the S lenses, meant for small sensors like the 20D and the Rebel. I would assume that the Sigma FOV would be for a full 35mm frame. |
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01/05/2005 12:29:41 AM · #3 |
The Canon 10-22 is an EF-S lens covering a smaller image circle than the Sigma 12-24 which is a full frame lens.
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01/05/2005 03:36:58 PM · #4 |
So, does this mean that on a Digital Rebel the Canon 10-22 will still be wider than the Sigma? I'm confused.
June
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01/05/2005 03:49:17 PM · #5 |
Originally posted by chiqui74:
So, does this mean that on a Digital Rebel the Canon 10-22 will still be wider than the Sigma? I'm confused.
June |
Yes, if you compare the Canon 10-22 to the Sigma both on the Rebel the 10-22 will have a larger field of view. Taking in for acount the 1.6 crop factor of the Rebel the field of view for the Sigma would be about 76 degrees. 122/1.6 |
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01/05/2005 03:54:24 PM · #6 |
June,
What determines how "wide" the lens is is the size of the sensor, or the "film". If you have a cam with a sensor of, say, a tiny, tiny 1/2 x 1 inch, and place on it a lens designed to "cover" a sensor of, say, 1x2 inches (these are arbitrary figures), you can see that with the smaller sensor you are effectively "cropping out" a relatively small section of what the lens is projecting, and making it "less of a wide angle/more of a telephoto."
It may make more sens to view this in terms of the film world; in a 35 mm camera, a 28 mm lens is wide angle. To cover the same "angle" in a 4x5 camera, you need a 90 mm lens.
Lenses are (usually) designed to a specific format, so that the image circle they throw is precisely tangent to the corners of the sensor or film rectangle. So I couldn't take a 90 mm lens from a Canon, mount it on my 4x5 camera, and get a 4x5 image; it would project a much smaller circular image in the middle of the film. So a 90mm lens designed for 4x5 camera work has a much wider "field" than one designed for a 35 mm camera.
This is important because the more you limit the field a lens has to cover, the more precisely you can tune your optics.
That's an overview. If you need more, let me know.
Robt.
Message edited by author 2005-01-05 15:55:18.
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01/05/2005 04:04:50 PM · #7 |
BTW the 10-22 lens is pretty neat. It is really hard to make a good wide angle lens, telephoto lenses are much easier.
The S series of lenses will only work with the Rebel and the 20D, the back of the lens sticks further into the camera and it needs the small mirror that these cameras use to work. Like all of the S lenses series it has great center sharpness but looses a lot of clarity at the extreme corners.
Here is a link that has the specification for the lens, I am a bit of a junky for MTF plots.
Canon 10-22 specs
Note this is from there Japanese web site, the English site does not have the full specs.
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01/07/2005 09:10:17 AM · #8 |
Originally posted by bear_music:
June,
What determines how "wide" the lens is is the size of the sensor, or the "film". If you have a cam with a sensor of, say, a tiny, tiny 1/2 x 1 inch, and place on it a lens designed to "cover" a sensor of, say, 1x2 inches (these are arbitrary figures), you can see that with the smaller sensor you are effectively "cropping out" a relatively small section of what the lens is projecting, and making it "less of a wide angle/more of a telephoto."
It may make more sens to view this in terms of the film world; in a 35 mm camera, a 28 mm lens is wide angle. To cover the same "angle" in a 4x5 camera, you need a 90 mm lens.
Lenses are (usually) designed to a specific format, so that the image circle they throw is precisely tangent to the corners of the sensor or film rectangle. So I couldn't take a 90 mm lens from a Canon, mount it on my 4x5 camera, and get a 4x5 image; it would project a much smaller circular image in the middle of the film. So a 90mm lens designed for 4x5 camera work has a much wider "field" than one designed for a 35 mm camera.
This is important because the more you limit the field a lens has to cover, the more precisely you can tune your optics.
That's an overview. If you need more, let me know.
Robt. |
So, an 80mm lens on a 6x6 camera is wide angle?
June
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01/07/2005 12:04:30 PM · #9 |
June,
The 80 mm on 6x6 (medium format film) is pretty close to a "normal" lens. Roughly the equvalent of a 55mm on a 35 mm camera if I recall correctly. Been a while. I could look it up....
Robt.
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