Is the aperture comparable?
Hello,
I have been asking myself this theoretical question for some time, and it may well be that there is a logical error here, but first the explanation:
Can you really compare the aperture value of different lenses?
After all, a 49mm lens with an f/1.8 aperture lets in less light than an 82mm lens with the same aperture. Right?
Which, according to my assertion, means that the noise performance should be better with an 82mm lens and wide aperture due to more light than with a 49mm lens. Of course, with the same camera and the same sensor.
Whether for APS-C, Super 35mm or full format is irrelevant for the comparison, as long as both lenses are for the same sensor.
Thanks for your answers,
Felix
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You forget the focal length of the lens.
The diaphragm value expresses the ratio between the focal length of the objective and the diameter of the entrance pupil and is defined by the equation N='/D. Thus, the aperture number (N) is equal to the focal length (') divided by the diameter (D) of the inlet pupil in mm. Don't be confused with the filter diameter you specified above!
An objective having a focal length of 50 mm thus has a light intensity of f/2 at a diaphragm aperture of 25 mm. If the lens had a larger aperture, it can logically not have the same light intensity, but becomes lighter.
The aperture number indicates the ratio of focal length to the size of the aperture. The necessary diameter of the front lens of the objective results from the focal length, the sensor size and the structural length.
Thus, if the losses arise, for example, due to the compensation of the lenses, which are anyway minimal, the transmitted amount of light per mm2 is sensor or sensor. Film area absolutely comparable.
Hi.
the apertures are 100% comparable, since here not somehow a random value is selected, but calculates: parts the focal length of your objective by the diameter of the light inlet opening thus the diameter of the front lens.
VG Hdhdidb
The diaphragm value is first of all a break of the indication of how much of the light falling in front comes out back.
If we assume that the two lenses are used at the same time at the same place with equally strong incident light, then they would also be approximately the same. (There always comes a certain fraction of the existing light out at the back of a certain aperture. And with another diaphragm, more or less.)
The diameter of the lenses does not matter with a given aperture. Because the diaphragms are designed as it is the same.
Your consideration would be correct if the hole in the aperture is always at a certain aperture value the same size in all lenses . But it is so adapted for each lens that it comes to the different lenses.
I don't know if there's exactly 1/8 of the light at aperture 8. Blend 8 and aperture 16 leagues at least 2 aperture stages apart, therefore only 1/4 as much light falls on the sensor at aperture 8. This is already logical because the surface of the pupil circle of the diaphragm is square to the opening.
I have adjusted this in the answer and expressed it more generally, so that it does not contain false figures.
Thank you!
Right. I have also done a little hard to explain it lamely so that the idea behind it becomes clear.
Like you're writing, there's something more behind it. It's about the area of the circle at the aperture.
No, because image noise is determined by the ISO, correct exposure (especially not underexposed) and comes to the motif / background (dark spots more)
I mean that with a larger diameter of the lens with its own aperture, as with a smaller, more light passes through, and thus, with its light, the ISO is better in the photo with a more diameter lens than in the smaller lens.
I'd say Blende's blind. But of course, it is so that, for example, long lenses (at the same time often more diameters) swallow some light. The sensor is also required because of ISO. Specifies normal sensors and BSI sensors that can use the light a little better.
Thus, it is true that the diaphragm is installed at the rear opening of an objective and has nothing to do with the filter diameter at the front.
And I could imagine that the diaphragm is also structurally adapted to the size of different sensor sizes.
Therefore, the same amount of light should always fall on the corresponding sensor. 💁🏻