A2 and focus

Sylvain52 · Feb 23, 2005

Don’t be afraid, I do not launch an other thread about OOF of the A2; this forum has fully dealt with this subject.

I have a question about the information the A2 consider to focus. Does it create a luminance information from the chrominance CCD information and use this luminance to focus or does it work only on a chrominance channel.

I tried to focus indoor in low light condition with my A2 on a very smooth vertical line of a red wallpaper. It took time to focus but it succeeded. I have been very impressed because the contrast seemed to be very low.

Then I tried to focus on a more contrasted (for me) greenish vertical line of a table. The A2 did not succeed to focus.
Does it mean that the A2 does not use the green channel to focus ?
Does anybody know which information the A2 consider to focus ?

Thank you for your answers.

Sylvain

Barrie Davis · Feb 23, 2005

Sylvain52 said:
Don’t be afraid, I do not launch an other thread about OOF of the
A2; this forum has fully dealt with this subject.

I have a question about the information the A2 consider to focus.
Does it create a luminance information from the chrominance CCD
information and use this luminance to focus or does it work only on
a chrominance channel.

I tried to focus indoor in low light condition with my A2 on a very
smooth vertical line of a red wallpaper. It took time to focus but
it succeeded. I have been very impressed because the contrast
seemed to be very low.
Then I tried to focus on a more contrasted (for me) greenish
vertical line of a table. The A2 did not succeed to focus.
Does it mean that the A2 does not use the green channel to focus ?
Does anybody know which information the A2 consider to focus ?

Thank you for your answers.

Sylvain

--
Sylvain,

Yours is reasonable enough question -- something I have thought about myself.

I don't have the answer for you, I'm afraid. Perhaps that will come from someone else. (???)

I only know what you know -- that the A2 contrast seeking algorithms work on VERTICAL contrast boundaries..... (or horizontal ones if the camera is used sideways).

What I have assumed is the algorithms find the greatest contrast across the channels, and then work with the colour channel that provides most contrast.

Please note: This isn't knowledge -- I'm just guessing .... ;-)

Regards,
Baz

André BARELIER · Feb 23, 2005

Hi Sylvain,

This is an interesting question. Unfortunately, I don't have my A2 to do some testing.
Maybe someone else around here ?
André

Sylvain52 said:
Don’t be afraid, I do not launch an other thread about OOF of the
A2; this forum has fully dealt with this subject.

I have a question about the information the A2 consider to focus.
Does it create a luminance information from the chrominance CCD
information and use this luminance to focus or does it work only on
a chrominance channel.

I tried to focus indoor in low light condition with my A2 on a very
smooth vertical line of a red wallpaper. It took time to focus but
it succeeded. I have been very impressed because the contrast
seemed to be very low.
Then I tried to focus on a more contrasted (for me) greenish
vertical line of a table. The A2 did not succeed to focus.
Does it mean that the A2 does not use the green channel to focus ?
Does anybody know which information the A2 consider to focus ?

Thank you for your answers.

Sylvain

--
André

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