HDRI Digest, Vol 48, Issue 1

hdri
1

Hi Greg and Axel,

Thank you so much for your input. Both methods seem to work although I'm still a bit confused on the ASA setting.

Greg, in your comment:

Usually the only information missing is the ASA, and this can usually be solved by choosing an ASA that is 1 EV higher.

Do you have an example you might be able to offer that I can work from? I'm not sure how to work out an ASA from an exposure value. Would the ASA value change with each bracketed exposure? I'm still scratching my brain cells around some of this and am not sure yet how to interrupt sensor sensitivity from these Machine Video cameras and the various settings the interface allows one to control.

Thanks again!

Cheers,
Chris

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Today's Topics:

  1. adding EXIF headers to JPEGS (Humann Chris)
  2. Re: adding EXIF headers to JPEGS (Axel Jacobs)
  3. Re: adding EXIF headers to JPEGS (Gregory J. Ward)

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Message: 1
Date: Fri, 20 Apr 2012 15:13:31 -0700
From: Humann Chris <[email protected]>
To: [email protected]
Subject: [HDRI] adding EXIF headers to JPEGS
Message-ID: <[email protected]>
Content-Type: text/plain; charset="us-ascii"; Format="flowed";
  DelSp="yes"

Dear Group,

I'm using an Industrial video camera to capture exposure bracketed JPG
stills that I'd like to turn into HDR images. The problem that I'm
having is that HDRgen and Photosphere both throw an error:
from HDRgen=
phdrimg.cpp@560>data: fc2_save_2012-04-20-202102-0000.jpg: needs
exposure calibration

or from Photoshpere=
Inkown image exposure(s)

using Exiftool I've tried writing to the header in each JPG like so:
exiftool -ExposureTime='1/5' image_1.jpg

However I continue to get the same exposure errors. Is there more
that I need to add into the Header? Below is the header printed from
exiftool for a sample JPG taken by the camer:
==> exiftool -h fimage_1.jpg
<!-- image_1.jpg -->
<table>
<tr><td>ExifTool Version Number</td><td>8.88</td></tr>
<tr><td>File Name</td><td>fc2_save_2012-04-20-202102-0000.jpg</td></>
<tr><td>Directory</td><td>.</td></tr>
<tr><td>File Size</td><td>637 kB</td></tr>
<tr><td>File Modification Date/Time</td><td>2012:04:20 14:48:31-07:00</
></tr>
<tr><td>File Permissions</td><td>rwxr-----</td></tr>
<tr><td>File Type</td><td>JPEG</td></tr>
<tr><td>MIME Type</td><td>image/jpeg</td></tr>
<tr><td>JFIF Version</td><td>1.01</td></tr>
<tr><td>Exif Byte Order</td><td>Big-endian (Motorola, MM)</td></tr>
<tr><td>X Resolution</td><td>72</td></tr>
<tr><td>Y Resolution</td><td>72</td></tr>
<tr><td>Resolution Unit</td><td>inches</td></tr>
<tr><td>Y Cb Cr Positioning</td><td>Centered</td></tr>
<tr><td>Exposure Time</td><td>1/60</td></tr>
<tr><td>Exif Version</td><td>0230</td></tr>
<tr><td>Components Configuration</td><td>Y, Cb, Cr, -</td></tr>
<tr><td>Flashpix Version</td><td>0100</td></tr>
<tr><td>Color Space</td><td>Uncalibrated</td></tr>
<tr><td>Image Width</td><td>1280</td></tr>
<tr><td>Image Height</td><td>960</td></tr>
<tr><td>Encoding Process</td><td>Baseline DCT, Huffman coding</td></>
<tr><td>Bits Per Sample</td><td>8</td></tr>
<tr><td>Color Components</td><td>3</td></tr>
<tr><td>Y Cb Cr Sub Sampling</td><td>YCbCr4:2:0 (2 2)</td></tr>
<tr><td>Shutter Speed</td><td>1/60</td></tr>
<tr><td>Image Size</td><td>1280x960</td></tr>
</table>

As always thanks for any info or help.

Kind regards,
Chris

Christian Humann ~ Associate
LOISOS + UBBELOHDE
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1917 Clement Avenue Building 10A
Alameda, CA 94501 USA
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Message: 2
Date: Fri, 20 Apr 2012 23:41:47 +0100
From: Axel Jacobs <[email protected]>
To: High Dynamic Range Imaging <[email protected]>
Subject: Re: [HDRI] adding EXIF headers to JPEGS
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Chris,

using Exiftool I've tried writing to the header in each JPG like so:
exiftool -ExposureTime='1/5' image_1.jpg

However I continue to get the same exposure errors. Is there more that I
need to add into the Header?

hdrgen need the following info:

- ExposureTime
- ISO
- FNumber

If it still fails, try writing the ExposureTime as floating-point
seconds; but I think fractions are fine.

Axel

------------------------------

Message: 3
Date: Fri, 20 Apr 2012 15:56:21 -0700
From: "Gregory J. Ward" <[email protected]>
To: High Dynamic Range Imaging <[email protected]>
Subject: Re: [HDRI] adding EXIF headers to JPEGS
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii

Hi Chris,

You can also substitute the -s option in the case of hdrgen (not Photosphere, though). This sets the exposure multiplier explicitly. You can estimate this from the known camera parameters using:

    Kfactor = 87.;
    stonits = Kfactor * aperture*aperture / (exptime * asa);

where aperture is in f-stops and exptime is in seconds.

That way, you don't need exiftool. Usually the only information missing is the ASA, and this can usually be solved by choosing an ASA that is 1 EV higher.

Cheers,
-Greg

------------------------------

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End of HDRI Digest, Vol 48, Issue 1
***********************************

Christian Humann ~ Associate
LOISOS + UBBELOHDE
- - - - - - - - - - - - - - - - - - - - - - - - - - -
1917 Clement Avenue Building 10A
Alameda, CA 94501 USA
- - - - - - - - - - - - - - - - - - - - - - - - - - -
510 521 3800 VOICE
510 521 3820 FAX
- - - - - - - - - - - - - - - - - - - - - - - - - - -

ยทยทยท

On Apr 21, 2012, at 12:00 PM, [email protected] wrote: