How to set AFL(autofocus locking) in libgphoto2

[lwj0216]

Hi, I am developing a application and using Nikon D3300 controlled by libgphoto2 on ubuntu14.04. I found that the camera couldn't auto focus successfully in the darkness, so that the method capture_to_file() return failed code and print error message: "Context Error, Out Of Focus". I wonder if there is a way to set AFL by linux shell command or c/c++ code. My idea is that calling AFL method when calling autofocus method return GP_OK in brightness and then turn to darkness so the camera can take a picture successfully. Thank you!

[msmeissn]

there is the "aelaflmode" config variable, ... However it seems as if the D3300 does not expose it via its API . :/

[lwj0216]

Thank you for your reply and i am so sorry for that i didn't notice your anwser. It has been confirmed that the D3300 does not support AFL via its API. So i tried to capture the image in LiveView mode and it did work for me. But now i meet some problem when i using gp_camera_capture_preview to get preview image data in a while loop and i get the error message below: // error log start errordumper error:Writing 16 = 0x10 bytes to port failed: Error writing to the port (-35) errordumper error:PTP_OC 0x1015 sending req failed: Error writing to the port (-35) errordumper error:Writing 16 = 0x10 bytes to port failed: Error writing to the port (-35) errordumper error:PTP_OC 0x1015 sending req failed: Error writing to the port (-35) errordumper error:Writing 16 = 0x10 bytes to port failed: Error writing to the port (-35) errordumper error:PTP_OC 0x1016 sending req failed: Error writing to the port (-35) errordumper error:Writing 16 = 0x10 bytes to port failed: Error writing to the port (-35) errordumper error:PTP_OC 0x1016 sending req failed: Error writing to the port (-35) errordumper error:'ptp_setdevicepropvalue (params, PTP_DPC_NIKON_RecordingMedia, &value, PTP_DTC_UINT8)' failed: PTP I/O Error (0x02ff) errordumper error:Writing 12 = 0xc bytes to port failed: Error writing to the port (-35) errordumper error:PTP_OC 0x9201 sending req failed: Error writing to the port (-35) errordumper error:Writing 12 = 0xc bytes to port failed: Error writing to the port (-35) errordumper error:PTP_OC 0x9201 sending req failed: Error writing to the port (-35) errordumper error:'ret' failed: Nikon enable liveview failed (0x02ff: PTP I/O Error) errordumper error:Nikon enable liveview failed (0x02ff: PTP I/O Error)

* Contexterror *
Nikon enable liveview failed (0x02ff: PTP I/O Error) errordumper error:'camera->functions->capture_preview ( camera, file, context)' failed: -7 // error log end The code is sometimes normal but sometimes i just meet the error presented above. That is my code snippet: while(this->mCaptureFlag) { CameraFile _file; char * imageData; retval = gp_file_new(&file); retval = gp_camera_capture_preview(this->mCamera, file, this->mContext); if (retval != GP_OK) { Log::getInstance()->error(TAG, "gp_camera_capture_preview failed..."); break; } else { retval = gp_file_get_data_andsize(file, (const char)&imageData, &imageSize); if(retval != GP_OK) { Log::getInstance()->error(TAG, "gp_file_get_data_and_size failed..."); } char data = (char *) malloc(imageSize); memcpy(data, imageData, imageSize); gp_file_unref(file);

    if(this->isFinishedFrame)
    {
        this->isFinishedFrame = false;
        emit signalSendToVideoThread(data, imageSize);
    }
    else
    {
        delete data;
    }
}
QThread::msleep(20);

}

I wonder if i didn't use the api well, thus the application went wrong ? Thank you for your reply.