Auto Exposure

[Goju-Ryu]

Hello!

I'm needing an auto exposure .vi. Can anyone give me one or indicate how to do it?

Thanks in advance!

[kamalb]

Hi

http://venus.ni.com/stage/utf8/niepd_web_display.DISPLAY_EPD4?p_answer=&p_guid=B45EACE3D8D356A4E0340...

Kamal
NIF

[Goju-Ryu]

Hi!

kamalb, thank you very much for your answer but I'm not having success opening the link you gave me...

Am I the only one having this problem?
Any sugestion?

Thank you very much for any help given.

[Goju-Ryu]

Hello!

Sorry for disturbing you again with this problem, but I'm still needing a auto exposure .vi or an algorithm that explains how to do it.

I don't know how to set programmatically the black and white reference levels...

Any help would be greatly appreciated!

Thanks in advance!

[kamalb]

HI

I advise you to post a new forum for your question..

Thanks
Kamal
NIF

[Goju-Ryu]

Hi!

kamalb, thanks for your advice.
But in which forum should I post this question? Isn't it a machine vision problem? I searched through the others and I don't see in which should I post.

Can you please give me some more help on this in order to direct my question correctly and get the desired feedback?

[Former NI Employee MS]

Hello Goju-Ryu,

My colleague Kamalb just thought you had asked for a new question. That's why he suggested you to create a new thread. As it is the same question, don't take his remark into account.

Regarding your concern, I am trying to get you the VI that was in the link. I am currently trying to see why the external link we could provide you is not working, and if it is a mistake or something volunteer.

I'll keep you informed very soon

Best regards

[Goju-Ryu]

Ok!
Thanks in advance for your help!

I'll wait then for your answer on this.

Best regards!

[Former NI Employee MS]

Hello back Goju-Ryu,

I am coming back with more information. Note that this is available using camera that return analog signal...

The example that is not accessible anymore is kept in internal because it uses obsolete VIs. The principle of it was the following:

---

This example programmatically sets auto exposure values for your IMAQ device. This VI produces the same result as manually assigning these values in Measurement & Automation Explorer (MAX). Auto Exposure.vi uses the same algorithm as MAX by taking a snap using the largest range of voltage levels (no gain), analyzes the image's histogram to find the range of pixel values, and adjusts the white and black voltage levels in order to get 98% of the pixels in the range (excluding the top and bottom 1% of pixels).

---

What was realized is:

1. Open IMAQ session

2. According to the used board: Set Black Reference to minimum and White reference to the maximum. Note that all boards don't have the same maximum White reference voltage, and that all boards don't allow you to change the Black Reference one.

3. Take a snap

4. Analyse the image using histogram, and determine a range within which 98% of the pixels are in

5. Set White Reference and Black Reference according to the previously determined range

What is obsolete (still supported however) is the call to the "IMAQ attribute.vi" that was used to get White/Black References. Now, this can be done using Properties Nodes on the IMAQ session you open in step 1.

Hope this helps

Keep me informed

Best regards,

[Goju-Ryu]

First of all thank you very much for your help!

Just a question about it, how do I convert the gray intensity values (the range limits) into reference voltages? What is the applied transformation?

I'm using a PCI-1409 and 8 bits images. Should I divide the voltage range by the 255 intensity levels?

Thanks in advance!