Determining dynamic range - attempt of a different approach

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Iliah Borg
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Determining dynamic range - attempt of a different approach
5 months ago

For D4s, the upper limit of the data in 14-bit uncompressed mode is 2^14-1-768 = 15615, where 768 is the black level. The setup for the following is: halogen lights, CTB-filtered, stabilized, Zeiss 2/100, f/5.6 with deep Lee hood, camera viewfinder closed to prevent stray light, camera set to ISO 100. Below are the readings from raw data from 3 shots of Sekonic 9-patch exposure profile target  taken with 1 stop between the shots (the total series is 12 shots). A1 is the lighter gray patch (#2 in Sekonic manual), G1 is the darker gray patch (#8 in Sekonic manual). deltaEV between patches is close to 1/6. Due to the arrangement the readings from G1 patch are very close to the readings from A1 patch exposed 1 stop lower.

Patch Ravg Gavg Bavg G2avg Gavg/Ravg Gavg/Bavg Gavg/G2avg

A1 9487.64 15566.62 10079.13 15599.24 1.64072625 1.54444084 0.997908872

B1 8524.77 14739.61 9116.65 14692.92 1.729033159 1.61677919 1.003177721

C1 7549.83 13004.01 8021.58 12955.13 1.722424214 1.621128257 1.003773023

D1 6681.15 11496.21 7095.06 11458.77 1.720693294 1.620311879 1.003267366

E1 5890.33 10158.3 6281.12 10138.37 1.724572307 1.617275263 1.001965799

F1 5447.39 9379.88 5786.49 9369.36 1.721903517 1.620996494 1.001122809

G1 4744.66 8157.47 5023.21 8143.41 1.719294955 1.623955598 1.001726549

A1 4697.16 8119 4986.53 8087.95 1.728491259 1.628186334 1.003839045

B1 4222.31 7311.84 4512.45 7287.08 1.731715577 1.620370309 1.003397794

C1 3744.94 6444.63 3972.07 6418.87 1.720890054 1.622486512 1.004013167

D1 3316.77 5692.71 3514.95 5672.6 1.716341501 1.619570691 1.003545112

E1 2925.97 5031.25 3116.83 5023.14 1.719515238 1.614220217 1.001614528

F1 2708.5 4644.83 2872.92 4640.06 1.714908621 1.616762736 1.001028004

G1 2360.92 4042.01 2495.3 4036.14 1.712048693 1.619849317 1.00145436

A1 2341.39 4025.53 2477.74 4009.18 1.719290678 1.624678134 1.004078141

B1 2106.8 3626.36 2244.34 3611.9 1.721264477 1.61578014 1.004003433

C1 1866.37 3198.42 1976.24 3187.55 1.713711643 1.618437032 1.003410143

D1 1655.87 2828.17 1750.71 2818.59 1.707966205 1.615441735 1.003398863

E1 1458.88 2501.64 1553.78 2495.9 1.714767493 1.610034883 1.002299772

F1 1350.47 2309.9 1430.44 2308.23 1.71044155 1.614817818 1.000723498

G1 1178.2 2013.25 1242.57 2008.41 1.708750637 1.620230651 1.002409867

The values on A1 on the first shot are below 15615, and the histogram of the green channels of the patch looks like a nice distribution:

However the G/R and other ratios show that for the A1 patch on the first shot the linearity is not there, and the linearity limit is somewhere around 15000, and some may insist that it is even lower, 14500.

Looking at the data from the last shot of what is total of 12-stop spread,

A1 3.8895 7.1369 3.9213 7.0167 1.834914513 1.820034172 1.01713056

B1 3.4922 6.5508 3.412 6.3752 1.875837581 1.91992966 1.027544234

C1 3.1931 6.0387 3.1151 5.9041 1.891171589 1.938525248 1.022797717

D1 2.9666 5.4871 2.78 5.4979 1.849625834 1.973776978 0.998035614

E1 2.6071 5.0895 2.6112 5.0718 1.952169077 1.94910386 1.003489885

F1 2.4389 5.0094 2.3532 4.6755 2.053958752 2.128760836 1.071414822

G1 2.2532 4.6077 2.2147 4.4927 2.044958282 2.080507518 1.02559708

It is pretty obvious that at least for the last stop non-linearities (including those caused by flare and glare) take the toll and linearity is broken strongly. Which leaves about 11 stops of dynamic range before the crossover of white balance.

A more stringent photographer may consider that the white balance irregularities causing colour problems in shadows in this experiment start from the raw level of 100. That means slightly more than 7 stops dynamic range for accurate colour reproduction.

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