ALC/ELC Function Explanation

[LDB 0]

I am one of a group of people using security cameras for astronomy. The cameras I use is a modified Mintron called a Mallincam http://mallincam.tripod.com/index.html

 

Several of us are working on a new program to remotely control the cameras with a PC. I am writing a user manual for the program. The project is almost finished but I still have a problem understanding the ALC function with auto iris lenses. ALC level is supposed to control the lens iris while ELC controls CCD sensitivity. As it is with the cameras on a non auto iris lens the ALC and ELC Level functions are linked in the cameras firmware. When ELC is increased ALC is also increased. When using the camera on a telescope or other non auto iris lens ALC Level is just ignored.

 

My question is if an auto iris lens is used with the camera will the link between ALC and ELC levels stop? Will ALC Level and ELC Level function independently? Could ALC and ELC be set to different levels if there is an auto iris lens plunged into the camera?

 

If you are interested in our use of the cameras, here's a link to my observatory. http://www.mts.net/~lmlod/Observatory.html

 

Thanks

 

LDB

 

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[Soundy 1]

According to Pentax's glossary, ALC is "An adjustment on video iris lenses also known as the "average to peak" control. This allows iris compensation for bright spots within the field of view either by exposing for them in particular (peak) or by taking an average across the entire scene." (http://www.pentaxcctvus.com/learn/index.html) - I don't believe the ALC should actually affect the image, as it should specifically relate to iris operation. It may be that it provides "peak vs. average" feedback to the camera, although that too shouldn't affect anything without an AI lens attached.

 

It's possible, since these are highly customized cameras, that they have different, specific operation of the ALC, beyond the standard definition... that would probably be a question better directed at Mallincam.