From: Milton Aupperle <milton@outcastsoft.com>

Date: May 2, 2009 10:11:45 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] fire-i : saturation of red channel

Dear Malte;

What your seeing is "normal", and has been that way since probably Astro IIDC 1.00 or maybe 2.0 was released. It isn't really a monochrome mode, we just extract the R, G and B color channel data from the Color image and output it that way.

When you have a color IIDC low end camera (i.e. Unibrain, Orange Micro etc.) and switch to one of the monochrome modes we are setting the:

Saturation to 28

Blue Gain slider to 90

Red Gain Slider to 45

I really do not know why I did that and I suspect I had a good reason at the time, but it was so long ago that I played with that code I don't remember the rationale behind it. It is easy to remove that code (just did it) as it only affects the low end Unibrain et all cameras, so it's easy to confirm this doesn't break any other cameras.

As to dynamic range, the low end Unibrain et al are only 7 bit camera on each color channel. This is because TI did not connect up one of the data lines in the TSLBV1501 chip set and you only get values out in pairs. So you might get brightness values of 244 and 245 or 248 and 249, but there will be no 246 or 247. And the Gain sliders change the actual values out, so at one gain setting you won't get say 200, but adjust the gain and will get 200, but maybe not 201 or 202.

Contact me off list at

support@outcastsoft.com

and I'll see what we can do about resolving it for you.

HTH..

Milton Aupperle

On 2-May-09, at 4:12 AM, maltetewes wrote:

Hi all,

I'm using an inexpensive unibrain fire-i colour camera (640x480 8bit) with the latest Astro IIDC 4.04.00, and have troubles with the dynamic range / saturation. First off all, let me say that I don't believe that these issues are related to this or that recent update of Astro IIDC, as I would have noticed this and I observe them for some time now.

As it's probably more a general question, I thought let's post this here.

The easiest-to-describe symptom is that using the "Red Channel Monochrome" mode, I can't get the saturation to happen on the right ("white") edge of the histogram. Saturation occurs somewhere at two thirds (181/255) of the dynamic range, independently of my adjustments of Brightness, Black Point, and Exposure.

Is there any extra setting/preference that I am missing ? It does not depend on the "Enable CCD Over Drive register optimization" checkbox.

Using the Green or Blue Channel Monochrome mode, the behaviour is different : a low position of the "Brightness" slider makes the image saturate below 255 if exposition time is too high, but all I have to do is to move this brightness slider towards higher values and the saturation peak in the histogramm can be brought "beyond" 255. If I then reduce the exposure time to avoid saturation, I get more or less the full dynamic range on the screen, as it should.

If I switch to "Monochrome" mode, same problem : red still saturates at the same value (producing a sharp peak in the histogramm), whatever the setting of Brightness, Black Point, or Exposure time is. I just can't get 255-pixels on the sreen, even if I completely overexpose all I get is a grey at 231.

But in "Color" mode, the "Red Gain" slider alows me to perfectly adjust the saturation level, so that it occurs beyond 255. I can get well exposed images with full dynamic range, and a maximum value of 253 in the video preview. So I'm guessing my camera is ok.

Is there perhaps any way to tweak these gain sliders, or the way the colors are mixed, in the monochome-like modes, or does someone has similar experiences ?

Cheers,

Malte