Best and easy way to remove color casting

[Guest porco1962]

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I'm not satrisfied with color uniformity of M240 especially in corner area.

There is no magenta or cyan casting on my M240 found in M9, but I can easily see red casting in the corner.

I was using LCC tool on C1pro but it's rather hard work to get every lens's compensation data on every aperture.

 

And I finally found an easy way.

At first take a picture without lens. You should better to face camera to whity object.

In order to press shutter without lens, you have to hide 6bit sensor. I used L-R mount

adapter from 3rd party.

 

If you take picture it's already reddish in corner.(see attached picture)

This may be an intrinsic characteristic of camera's sensor.

 

Use C1pro to make LCC profile with this picture.

 

With this way, you can compensate color casting of various kind of lens in a mild and easy way.

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[Guest porco1962]

This article is strongly related to M240.

 

Why move this article?

 

I can't understand.

[BerndReini]

So let me get this straight, there is a color cast present even when you take a picture without a lens? Is this true? It makes absolutely no sense to me then why Leica doesn't compensate for this in advance in the sensor readout. Why make highly corrected lenses if the sensor isn't giving a somewhat uniform image? I think I need an explanation from someone like Michael, who knows what the reasoning behind this is.

 

And I fully agree with the OP that this should stay in the M forum. Can we just rephrase the headline to: Why is there a color cast without lenses? I am really interested to know. Don't color casts and vignetting usually differ with aperture and focal length due to the angle of incidence of the light falling on the sensor?

[Jeff S]

You should better to face camera to whity object.

 

Are you 100% certain about uniformity of color and lighting of target?

 

I remember shooting white cards with film Ms to determine film and development times, and it was harder than one might think to get absolute uniformity across the target.

 

Jeff

[BerndReini]

I agree that it isn't that simple to light an area uniformly, but the red at the corners would not result from uneven corners. In general, vignetting from light loss shouldn't result in color shifts. What is going on there?

[Guest porco1962]

I think you can easily do same test as I did.

 

You can easily find that without lens, sensor can see only ambient light color or brightness as a blurring image very very roughly.

 

So it does not matter you can arrange completely white board or walls.

 

The picture I attached before defenetely is a sensor intrinsic unevenness.

 

Please do your test with your M240 before saying something. I want to see result.

 

And again I request to moderator to move this thread back to M240 place.

[Guest porco1962]

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Hi BerndReini-san

 

Not like CCD, CMOS sensor has transistors in every pixels.

So there is an intrinsic uneveness due to gain variety of each pixel transistor.

So manufacturer should correct that unevenness with actual measured database for each piece of sensor.

 

I think Leica does not do that.

[k-hawinkler]

So, if I get this right you say:

 

M240 no lens on white surface: color cast.

M9 no lens on white surface: no color cast.

 

Thanks.

[Jeff S]

Please do your test with your M240 before saying something.

 

Too busy taking pics of real subjects, without problem, thanks.

 

Jeff