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01/18/2004 09:04:31 AM · #1 |
I have a question about DSLR and lenses. when you buy lenses for a dslr there is a multiplication factor for the focal length of the lens because the focal length depends of the size of the sensor. Is there a multiplication factor to evaluate you maximum aperture value too? Because from what I understand, the aperture depends of the size of the sensor too.
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01/18/2004 09:09:51 AM · #2 |
in a nutshell, no, the aperture has nothing directly to do with the sensor size. the aperture is just a ratio of the physical real focal length of the lens, divided by the diameter of the 'hole' the light is coming through. in other words, an aperture of f/16 means the hole is 1/16th the width of the focal length.
Using real numbers that means if you had a 16mm lens, at f/16 the aperture would be 1/16 of 16 or 1mm. At f/2, it would be 1/2 of 16mm or 8mm.
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01/18/2004 10:06:29 AM · #3 |
this thread is about the same subject sort of..
this thread
this may be of interest as well.
Details on the subject
the aperture should not be an issue, because the lenses will have the same focal length on either a dSLR, or a 35mm SLR ( the difference is the film plane size, and on a dSLR more is cropped due to the sensor size ( film plane size ), my camera for instance has a 1.6x crop factor ). but depending on the cameras sensor quality , and the lense quality, you may get some weird edges using wide open aperture, or wider angle lenses. i think this effect might be more prominant on a digital vs 35mm camera.
where the aperture is a factor is on longer focal length lenses, the longer the zoom used the less DOF you will get. also in order to get larger aperture or small Fstop on a longer lense the lenses need to be wider to allow the aperture to open wide enough. so using the example above f2 on a 300mm lense would be 100mm opening ( thats a huge opening as most lenses use 55, 58, 62mm filters... ) so lenses in longer focal lengths that offer wide apertures are very expensive..
Message edited by author 2004-01-18 10:07:33. |
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