How to find a pcomb -s

Hello, I am currently working on synthesizing HDR images and correcting luminance values using HDRgen programs.

pcomb -s K [input HDR file] > [output HDR file]

I want to use the above syntax to calibrate the luminance value, may I know how to get the K value?

To convert [The luminance value of the HDR file, 900] to [The measured by luminance meter, 4000cd/m^2], the calibration factor was entered as 4.4 and found to be 14,000 cd/m^2.
It was calculated as 4000/900 = 4.4, but I don’t think this is the way to calculate the correction factor.
Can you tell me how to find the exact correction factor?

Hi Yeo,

Welcome to the forum!

The K factor in your pcomb command should be computed by comparing an in-scene measurement of luminance taken at the same time as your capture. If you compare the luminance of that position in the image using either Photosphere or the ximage utility with the ‘L’ command explained in the ximage man page, then your K factor should be:

K = Luminance_Meter_Yvalue / ximage_Yvalue

and the command should be:

pcomb -s K -o input.hdr > output.hdr

The “-o” option ensures that the original exposure is taken into account prior to correction.

I hope this is clear enough.

Thank you for your response.
And when I edit the header

(getinfo < 04.hdr | sed “/VIEW/d” && getinfo - < 04.hdr ) > 05.hdr

The results are as follows :
sed: -e expression #1, char 1: unknown command: `?

Do you happen to know how to solve a problem like this?

Your quotes are not the ASCII characters, but something with formatting. Just hand-type the command and it should work. Don’t rely on cut-and-paste with these things.