Making HDR image from XYZ data

radiance-general
#1

Hi,

I’m new to this Radiance forum.

I have a question about a radiance system to generate HDR image.
Now, I use a system that can obtain XYZ data (Y is cd/㎡) from photographs taken with different exposures in real room. I am trying to create an HDR image from this data using the pvalue of radiance command. The commands I use are the following;
$ pvalue -r -h -pXYZ -y 3840 +x 3840 X.csv Y.csv Z.csv > output.hdr

However, compared to the actual image using Adobe Photoshop, I feel that the shape is similar but the color is incorrect. Actual photographs cannot be attached due to various reasons.

I would appreciate if you could tell me if any options are missing.

Thanks in advance.

#2

Hi Yusuke – welcome to the Radiance forum!

I think you are missing a “-d” option that you need for your pvalue command to work properly. Assuming your csv files contain color data but no commas, the following should work:

pvalue -r -h -d -pXYZ -y 3840 +x 3840 X.csv Y.csv Z.csv > output.hdr

If you send the top of each *.csv file, I can make sure it is in the expected format.
Then, your output file should be of the special format “32-bit_rle_xyze”, which not all programs fully support. To convert to a more standard “32-bit_rle_rgbe” you can use:

ra_xyze -r output.hdr outputrgb.hdr

Oddly enough, my version of Photoshop (CS 6) seems to understand the XYZ file just fine. I hope they didn’t break this in their more recent version…

#3

Hi Greg

Thank you for your reply immediately.

It worked fine by using the -d option.
Thank you for telling my missing.
Also, I can see the xyze format using Photoshop.

However, in the 32-bit format, it was overexposed. So I changed from 32-bit to 16-bit using photoshop. As a result, I was able to output successfully. I think this is because the camera using is recording in 12-bits.

#4

I’m glad you got it to work – excellent. The exposure of an HDR file can be adjusted with the pfilt -e option in Radiance. It is better than converting to 16-bits, which may make other alterations that affect accuracy.

#5

Hi

My name is Keisuke and I am a master’s student studying light at a university in Japan.

I also have a same question.

But, I’m a biginner of Radaiance.

so, Could you tell me how to use it.

はじめまして。
日本の大学で光の勉強をしている荒田と申します。
撮影した画像から得たピクセルごとの輝度データを用いて、HDRファイルを作成しようとしているのですが、その方法がわからず苦戦しているところ、Yusukeさんのコメントに巡り合いました。
Radainceについて、相談に乗っていただけないでしょうか。

荒田

#6

Welcome Keisuke,

Can you ask a question (in English), please? Google’s translation of the Japanese was not very useful as it also doesn’t appear to be a specific question.

If you need help getting started with Radiance as a complete novice, there are multiple places to look, though I admit they are not obvious and do not necessarily offer the kind of introduction you need to start working with HDR images. Please start from https://radiance-online.org/learning

We are here to offer guidance, but can’t really solve your problems for you.

#7

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#8

Hello, Keisuke.
I will rely in English here.
I am almost a beginner, regarding Radiance. So I also refer to the Radiance manual. First of all, how about trying it with reference to the manual? If you have questions, ask in the discourse and everyone will help.
If you have any questions to me, I will answer as much as possible.