Archived posting to the Leica Users Group, 2008/09/03

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Subject: [Leica] About to take M8 plunge - but worried about blownhighlights...
From: ken at iisaka.org (Ken Iisaka)
Date: Wed Sep 3 10:18:08 2008
References: <200809020336.AWF59279@rg4.comporium.net> <93642647159018605813317929417096646172-Webmail2@me.com> <D9D12C4801DB4B28BF9FB45512EBFB16@dadquad> <p06230908c4e45daa048e@10.0.1.199>

Actually, this occurs with transparency films as well.  Around the over
exposed highlights, you will see colour fringes, and that's mostly not
because of the chromatic aberrations.

On Wed, Sep 3, 2008 at 9:01 AM, Henning Wulff <henningw@archiphoto.com>wrote:

>
> Actually, the 'chromatic' issues around highlights are not a function of
> the lens, but of the sensor and the light qualities that hit it.
>
> Highlight blowout is due to sensor saturation, ie, the sensor cannot
> register the actual number of photons that have hit it as it's a number
> that's bigger than what it's maximum. Near the actual highlight, where 
> every
> channel is blown out, is a region where some channels are saturated, but 
> not
> other(s). That will give areas or rings around the highlights of colours
> that have not yet saturated. Because some channels have saturated in this
> region, the colours will be false as the saturated channels cannot provide
> the proper value.
>
> All digital sensors will do this, but unless the highlight areas are large
> with gradual transition areas, it won't be a problem. There are some
> workarounds, but they involve 'creating' some colour values in this region.
>



-- 
Ken Iisaka
first name at last name dot org or com

Replies: Reply from henningw at archiphoto.com (Henning Wulff) ([Leica] About to take M8 plunge - but worried about blownhighlights...)
Reply from mark at rabinergroup.com (Mark Rabiner) ([Leica] About to take M8 plunge - but worried about blownhighlights...)
In reply to: Message from images at comporium.net (Tina Manley) ([Leica] IMG: Playing with Fire)
Message from simonpj at mac.com (Wyndham Pulman-Jones) ([Leica] About to take M8 plunge - but worried about blown highlights...)
Message from hoppyman at bigpond.net.au (Geoff Hopkinson) ([Leica] About to take M8 plunge - but worried about blownhighlights...)