Special camera application issue

Question

Import EV Corporation OP

Created Sep ’22

Replies 3

Boosts 0

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I am having trouble with a special camera application and am posting to ask for your wisdom.

I am implementing a process to shoot 4k video in the AVFoundation framework. The app does not take video, but rather attaches a film camera shutter mechanism in front of the iPhone camera and acquires still images by the film camera shutter release.

For details, please visit the following web site;
https://www.digi-swap.com/

Until the film camera shutter is released, the iPhone camera gains a complete black image. When the shutter of the film camera is released, for example, the shutter speed is 1/30s, the image (light coming through the film camera's lens) for 1/30s is irradiated to the image sensor of the iPhone, and this image is acquired as a still image.

Naturally, there will be insufficient light, so the aperture of the iPhone camera is opened to maximum and a shutter speed of 1/1s or longer is used. Focus is also fixed.

When taking a picture under these conditions, the center of the still image is relatively bright, but the periphery is dark.

I guess the cause of this is a problem with less launching time of the iPhone camera from complete black to 1/30s light reception. In other words, it may be because the camera does not have enough time to capture a clean image.

I am hoping to confirm if my understanding is correct with the engineers who are developing the camera area at Apple, and hearing back from you would be highly appreciated.

Best regards,

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Answer 1

ssmith_c OP

Oct ’22

well, that looks like a fun application! Aren't you just seeing normal lens vignetting here? The image plane of the original film camera was evenly illuminated by the original lens (film cameras can't compensate for lens vignetting). The adapter interposes elements between that image plane and the iPhone's lens, such that light falling on the periphery of the plane follows a much different path than light falling on the center of the plane. You can and should compensate for the difference in image brightness in software.

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Answer 2

Import EV Corporation OP

Nov ’22

ssmith_c,

sorry for my late response.

Thank you for your response.

Yes, I understand what you are saying and you are right.

I can get much better picture when I record a video, but can not get the same quality for a still picture. So, I think the problem shows when I shoot a still picture. The reason may be less light, though.

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Answer 3

ssmith_c OP

Nov ’22

when you record a video, is the phone using the same field of view as for a still picture?

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