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Fixed Camera and Lens (Locked in Place on a Foba), but the Focal Length Changes in Exif Even Though


The exposure is also affected. About 10-15 points on the grey card reading. The exposure remains the same with a perfect grey card reading while this is not happening. It is studio lighting with no variables. As you can see in the image below, the focal length does not actually move. It is just the Exif data for the focal length that changes. For context, these cameras are hanging high pointed to the ground. The lens rings are locked in place externally. They have been fixed in the air for years. I'm wondering if there is damage to any part of the camera from this, or if it is a capture issue. Please let me know if anyone has experienced the same thing!


Screenshot 2024-01-16 at 10.17.59 AM copy.jpg



Thanks for joining the conversation, mainer77!

So that the Community can help you better, we need to know exactly which Canon camera and lens models you're using. That, and any other details you'd like to give will help the Community better understand your issue!

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Thanks and have a great day!

Hey Danny! This particular camera is a 5d Mark iii with a 24-105mm f4 L


A coworker and I did some research and stumbled upon a forum detailing incorrect exif data and how it can theoretically effect an image. Here is our working theory: the cameras being aimed down for extended periods slightly damaged whatever sensor or scale sends the focal length to the camera body. Because of this, when it is at 50mm, it periodically will tell the camera it is at 55mm. The same thing has happened previously with a different body lens combo (both were the same setup, 5D Mark iii and 24-105mm f4L). With the other setup, the exif would periodically switch from what I remember to be somewhere around 65mm to telling us it was at 105mm. The frame remained the same, but the over-exposure was extremely more severe. Our understanding for the discrepancy is that the built in lens corrections are enabled, therefor the camera is building a correction for the wrong focal length, effectively altering the exposure values. Our solution that we will be testing is to disable the lens correction settings in the camera bodies and allow Capture One 23 to run its lens corrections after the fact.

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