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Re: [OM] TOP - DxO Gives OM-D High Marks

Subject: Re: [OM] TOP - DxO Gives OM-D High Marks
From: John Lind <j-a-lind@xxxxxxxxxxx>
Date: Thu, 4 Oct 2012 11:42:36 -0400
My brain hurts now - going to have to read that several times after it recovers.

John

Sent from my iPhone

On Oct 4, 2012, at 10:54 AM, Ken Norton <ken@xxxxxxxxxxx> wrote:

>> I get that about film and filters.  But you said in a previous post in
>> this thread that "raw is not raw."  Are you making the case that we have
>> to shoot daylight WB and use filters with digital capture?
>> And if so, how does CaptureOne then come into the picture.
> 
> What I am implying is that the camera itself is providing color
> correction at the chip level to "normalize" the sensor to a
> standardized white balance. They also do a bit of tweaking to align
> the overall sensitivity to their normalized ISO settings. I won't get
> into how they determine standardized ISOs, but they do micro-adjust
> the gain on the sensor to bring it in line with not only WB
> standardizations but speed standardizations too. As has been proven
> through actual real-life usage, not everybody gets this right. My
> Minolta A1 is a good example of this, where the ISO setting of 100
> gives the exposure equivalent to ISO 160.
> 
> Onto the subject of using lens filters to color-correct a digital
> camera file as compared to doing the correction in post, well, this
> has been a subject of a lot of testing about ten years ago. What
> happened is that convenience and optical purity won out. Let's take
> the example of an indoor shoot under 3600K lights. You have a choice
> of placing a blue filter on the lens or do the correction later. When
> you use the blue filter, the noise in the blue channel stays lower,
> but the noise in the green and red channels go up. If you do it in
> post, the blue channel noise increases. However, one nasty side effect
> of NOT using color correction filters in this case is that we run a
> risk of blowing out the red channel (or even the green channels,
> depending on camera) which causes clipping and other artifacts. If you
> are shooting the entire project under 3600K lighting, and there is a
> lot of dynamic range to the scene, you actually do get better results
> if you use a CC filter. If you are under stage lighting, for example,
> that is 3600K, the highlight fringing/transitions of any lights in the
> scene are nasty in the digital files--especially if the lighting is
> red-gelled. A blue CC filter allows you to balance the lighting so
> that all three colors in the sensor will clip at or near the same
> point. The overall noise-level will increase since you have to
> increase exposure somehow, but the clip point and overall dynamic
> range is improved. (As a side note, stage lighting, thanks to LEDs has
> been shifting towards daylight white-balance and is no longer as warm
> as it used to be).
> 
> So, let's run this to a landscape shot where we KNOW we're going to
> warm up the image. Under cloudy conditions or right after sunset, the
> overall lighting will skew to the blues. We warm the image up with
> color correction via the white-balance adjustment. If we are
> photographing a scene (the waterfalls on our trip) where we have the
> bluish cast that needs correction and the scene itself contains
> highlights and shadows that need to be preserved, we can end up
> clipping one end or the other. A warming filter placed on the lens
> will allow us to effectively increase the dynamic range of the scene
> as captured on the sensor. Specifically to this, the shadows won't
> pick up a blue noise cast and dithering artifacts as you lean into the
> last two bits.
> 
> A third scenario, which is more unique to some cameras than others is
> that when the coloring of the scene is far too intense in one of the
> primary colors, bad things can happen. The DMC-L1 is a classic example
> of this. When the coloring of the scene contains too intense of
> oranges, it will just blow them right out. The E-1 isn't too far
> behind. Let's say that you are photographing a red rose. To keep the
> petals from blowing out, you have to underexpose the scene by
> sometimes multiple stops. Then you bring the exposure back up during
> post. If you don't do this, you end up with a bright red blob with no
> details and Moose rightfully complaining about it. If, however, you
> place a filter on the lens to de-red the scene a bit, you will bring
> the exposure range of the reds down and increase the greens or
> whatever else.
> 
> The idea which I'm presenting here is that we think of the sensor not
> as just one sensor, but three sensors. You have a green sensor, a blue
> sensor and a red sensor. Instead of exposing the picture based on the
> combination of all three colors (or in monochrome), you adjust your
> exposure so that none of the three color sensors is clipped on either
> end. Since you can't really expose them separately, what you would do
> is analyze the scene and determine which color sensor will clip and by
> how much and offset that with a filter of the opposite color.
> 
> Overall, this is more academic than practical. Few of us travel around
> with a set of CC filters. And in all honesty, it is a rare image which
> would really benefit from this level of attention.
> 
> -- 
> Ken Norton
> ken@xxxxxxxxxxx
> http://www.zone-10.com
> -- 
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