Timeline for Does my crop sensor camera actually turn my lenses into a longer focal length?
Current License: CC BY-SA 4.0
7 events
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| Jun 16, 2020 at 11:21 | history | edited | CommunityBot |
Commonmark migration
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| Jun 21, 2019 at 3:27 | comment | added | scottbb♦ | Your edit helped put the DoF & noise "equivalence" more up front. I just meant to emphasize that crop, when applied to f-number, doesn't change the exposure of a particular scene just because a crop sensor is being used. An EV 15 scene is still EV 15 — say, Tv = 1/1000 s, Av = f/5.6, doesn't need to be adjusted because of crop factor. However, in order to maintain equivalent DoF and apparent noise (as you well note) and maintain the same exposure with C = 1.6, then aperture needs to be adjusted by 2*log2(C) = 1.35 stops and ISO needs to be similarly adjust by 1.35 stops. | |
| Jun 20, 2019 at 16:48 | history | edited | juhist | CC BY-SA 4.0 |
explain what is maintained constant
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| Jun 20, 2019 at 16:47 | comment | added | juhist | I don't entirely understand the criticism. If you apply all of the transformations, you get (1) the same angle of view, (2) the same depth of field, (3) the same background blur, (4) the same noise (assuming equivalent sensor technology -- you can't compare a 20-year old sensor to a new sensor), (5) the same exposure. | |
| Jun 19, 2019 at 18:55 | comment | added | scottbb♦ | To be clear, except for the mention in your bullet points, there's no indication that crop factor applied only to DoF and noise with respect to aperture and ISO, respectively. I don't think anything you said is actually incorrect, just that I don't think you emphasized where crop only applies. | |
| Jun 19, 2019 at 18:53 | comment | added | scottbb♦ | I had to downvote for the following specific reasons: 1. You didn't make it clear that the effective focal length is fundamentally about field of view. The actual focal length of the lens (which is determined solely by the shapes, positions, and refractive properties of the lens elements) is not affected by crop factor. 2. Crop factor applied to aperture is with respect to depth of field only, not with respect to exposure. 3. Crop factor when applied to ISO (ISO-squares, as you noted) is with respect to image noise only; again, crop factor has no bearing when it comes to exposure. | |
| Jun 19, 2019 at 17:31 | history | answered | juhist | CC BY-SA 4.0 |