John Sadowsky

John Sadowsky

Charlestown, MD

John S. Sadowsky is a retired wireless system and signal processing engineer. After 15 years as a professor of Electrical Engineering (Purdue and Arizona State), in 1998 he moved to industry to participate in the rapid development of digital wireles...
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Figure 3:  Gamma level histograms with logarithmic vertical axis.

A Better Histogram

The photo-histogram is probably the most ubiquitous exposure tool in digital photography; that is, short light metering itself.  It has been with us more than 25 years, and it hasn’t changed much.  The histograms we are familiar with are calculated from transformed...

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  • John Sadowsky
    John Sadowsky
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    Posts: 25
    Capture One
    on: December 5, 2019 at 8:26 pm

    I’m in the process of researching the jump from Lr Classic to C1.  I only just downloaded the new C1 Pro 20 yesterday, but I did watch a few videos.  I wanted to test an adjustment that I just couldn’t do to my satisfaction in the Lr/Ps world.

    The attached image shows before and after C1 adjustments.  It was shot with an A7R III with a Zeiss Batis 18mm lens.  The images cropped to the area of interest.  The problem was a bright green flare you see clearly near the tree trunk on the right, but also in the triangle formed by the horizontal trunk and the two vertical branches in the upper center-left side of the image.  This is a difficult adjustment because the scene is complex (tree bark, twigs, …) and while the desired result is to eliminate the bright green flare, the scene also contains greens that you don’t want to distort.  Heal and clone tools are useless here.

    I tried for hours to do this correction in Lr.  In this instance, I needed to adjust a very narrow hue range (the saturated green flare), but Lr HSL has only 8 fixed hue ranges.  And worse, color adjustments for colors that fall in the boundary of two of those pre-defined ranges are addressed by ganging together two adjacent hue ranges.  So you are now adjusting a broader hue range, when what you might want it to concentrate on a narrow range of hue.  That just can’t address my problem:  get rid of the highly saturated green flare (a narrow hue range) without distorting the other greens in the image.

    I quickly realized how to do this with C1.  Step 1:  Create a color adjustment layer.  Step 2: Use the eyedropper to sample the most saturated part of the flare.  That defines an initial “color wedge” for the adjustment.  Step 3: Set the layer mask.  In this instance, I used 100% flow for the bright spot on the right, and a 30% flow with a light touch in the center-left region.  Step 4:  Desaturate (the green color wedge) a lot, and reduce the lightness a bit.  Step 5:  Tweek!  I adjusted the hue range of the color wedge for the best results.  That was important because I wanted to kill the saturated green hue of the flare without distorting the other greens in the image.

    I can’t say you can’t do this in the Lr/Ps world.  I can only say that the C1 tools were designed in a way to lead me straight to the solution I desired.  This is a tough adjustment, and yet I got it within days of the C1 learning curve.  Bravo C1!

    JSS

    • This topic was modified 9 hours, 33 minutes ago by John Sadowsky.
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    John Sadowsky
    John Sadowsky
    Participant
    Posts: 25
    Re: Replacing Photoshop – what works?
    Reply #1 on: December 3, 2019 at 6:53 pm

    And … at $50 you can’t beat the price of Affinity!

    JSS

    John Sadowsky
    John Sadowsky
    Participant
    Posts: 25
    Re: Creating Artistic Photographs Part 3
    Reply #2 on: November 17, 2019 at 8:26 pm

    Fascinating – I’ve heard that from a number of great photographers – that they learned from the brush artists.  We just moved from Mesa AZ to Maryland (to be close to grandchildren) – wish I’d connected with you when we were in AZ!  I used to do a lot of trips to southern UT.  What an enchanted land!

    JSS

    John Sadowsky
    John Sadowsky
    Participant
    Posts: 25
    Re: New Article Announcements & Discussions
    Reply #3 on: November 17, 2019 at 3:29 pm

    “Hyperrealism is to photography what manipulated photographs are to a painting.”  Well said!

    I am an O’Keeffe fan.  The O’Keefe museum in Santa Fe is a must see.  Growing up in the Chicago area, I was drawn to her work at the Art Institute.  I always found it interesting that she was married to Alfred Stieglitz, a photographer.  There had to be some really interesting interactions there between the brush artist and the photographer.

    JSS

    John Sadowsky
    John Sadowsky
    Participant
    Posts: 25
    Re: A Better Histogram, human vision?
    Reply #4 on: November 16, 2019 at 11:47 pm

    Ken – thanks.  The DR of the human eye is a contentious issue – there are some rather ugly threads on DPReview about this.  I hesitate to go to far down that rabbit hole.  I admit I have a narrow point of view about this.

    I believe a lot of the controversy comes from confusion adaptation with sensor DR.  I do not include adaptation in DR.  If we do include adaptation, the eye can adapt from night vision to brightest daylight over a range of more than 40 stops.  I don’t think anybody claims the DR of human vision is 40 stops.  There is a wide range of adaptations, some fast (like the iris) and some a lot slower.  Where do we draw the line between sensor DR and adaptation?  I claim we should do it the say way we do it for our cameras.  Adaptation (exposure and ISO) is not considered to be part of DR.  Its just the DR of the sensor.

    The high resolution fovea of the eye has only a 15 degree field of view.  Photoreceptors in the eye saturate at about 100 photons, which is where the 6.5 stops number comes from.  Our perception of vision is based on the fusion of many foveal image fragments that occurs in the occipital lobe of the brain.  Those image fragments can have different iris and perhaps other fast retinal adaptation.  The process of human vision perception is similar to HDR merging and tone mapping.  But like HDR merging and tone mapping, those different (iris or otherwise) adaptations on different foveal fragments have the effect of compressing a wide DR (that represented by the input foveal fragments) to a narrower DR that we actually perceive.  So much of this boils down to being precise about which DR are we referring to.  The total DR represented by all the foveal fragments before fusion, or the DR of the fused image that we perceive.

    The problem is that we can’t download images from our occipital lobes.  So we can’t easily measure the DR of perceived vision.  Still, I claim that DR is only 6-7 stops.  The best way to see this is with a stops gradient displayed on a high DR media.  However, here I offer two other arguments.  First, consider that our best prints can have DRs that fall in the range of ~6 stops (matte paper) to as much as 9 stops.  Most high end monitors have a 9 stop DR.  If we have the ability to actually see wider DR, then we would find those media to be much less satisfying.  Second, as I’ve shown in the article, the gamma levels used in post processing software (histograms and curve adjustments) only cover ~6.5 stops.  If the DR of vision perception was larger we see that deficiency in our post processing.

    Ok, that’s my defense.  Again I recognize that it is based on a narrow concept of DR of human vision, and there are other valid points of view.

    JSS