Also with mixed formats (both video and still photo images from the same camera). There are plenty of issues when trying to determine the sensor size of compact or phone cameras. An older prime lens (non-zoom) has the best chance, but zoom lenses and internal focusing lenses are the worst about reporting accurate focus distance (because then geometry inside the lens changes with zoom and focus). The lens distance possibly might be about correct sometimes, but it sure seems Not the way to bet. If using the reported distance, it needs to be measured and verified at the same zoom and focus distance you will be using. That article is about balanced flash problems trying to use the lens distance to control TTL direct flash exposure, but it applies here too for the same accuracy reason. For evidence to make this point, see this chart about measured distances vs what some high end lenses report for focus distance. The reported Focus Distance in the image Exif data is Often NOT very accurate (try a measured test to verify it at your same zoom focal length and a similar focus distance). We typically just guess at subject distance, I'm thinking likely often not within even 20%.If used when zoomed to some intermediate point, the actual focal length used is not known accurately. Zoom lenses only specify focal length at either zoom end.But if not familiar with the lens on a 35 mm film camera, then knowing this is of no use to you, If you knew what field of view that the equivalent lens showed on that camera, then you know what to expect your lens will also do on your camera, if you don't already. This might be informative if you are familiar with using 35 mm cameras. The concept of Equivalent focal length number is that it is instead only used by a hypothetical 35 mm film camera for it to then show the same field of view as your camera sees. However some online sites reporting cell phone specifications do report Equivalent focal length instead of the actual focal length. The real focal length of the normal lens of a cell phone camera is in the neighborhood of about 4 mm (or plus a fraction, but it depends on sensor size). Even if you see a few internet sites reporting your cell phone focal length to be around 26 to 28 mm, that is the Equivalent focal length, and IT IS WRONG for the real focal length of your phones actual lens. Only specify the real focal length of your actual cameras lens. Your camera DOES NOT EVER USE Equivalent Focal Length, so never specify that it was used.Otherwise, garbage in, garbage out.įirst, three very common mistakes to avoid: Calculations absolutely require accurate data. The math is correct, but you MUST have reasonable confidence and knowledge that your input data is in fact accurate data, or else you're wasting your time here. The data specifications that we think we discovered are often incorrect, again which is more likely true of phone and compact cameras than larger ones. I am trying to discourage attempts expecting that guessed or unknown inputs will produce meaningful accuracy. Camera specifications, if even specified, are rounded approximations. If your results don't seem reasonable, distrust and verify all of your inputs (including sensor size, focal length, crop factor, aspect ratio, and scene distance). It will tell you all I could repeat in email. Before bothering to start calculation here (especially Compact and phone camera users, which is the least likely success, due to difficulty of finding accurate camera specifications.) Please read the Help material below, plus the section following immediately next, for help determining the camera's sensor size and focal length values. But this is NOT an easy question about small cameras, at best difficult and requiring a bit of technical understanding. Best case for this, you will have a larger camera, like DSLR size, which typically do actually specify this data. The calculator is below, but there’s lots to get out of the way firstĪny meaningful accuracy needs you to be pretty confident that you do in fact actually know your cameras actual sensor size and focal length.
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