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Making A Dynamic Range Test - Right Track?


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#1 Macks Fiiod

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Posted 18 June 2018 - 09:19 AM

So I'm fed up with all the conflicting results on Google.

 

I have a plan for testing the DR of my various cameras, but I just want to make sure I'm doing this the right way:

 

Setting up the cameras in their native ISOs.

I'll take one of my Kino tubes, buy some Lee 0.3 ND, and progressively layer it from left to right, each time increasing how many strips of ND I put over a single area. Will have 20 different sections and meter for the middle section.

 

My questions are:

 

Should I make sure everything behind the tubes is matte black? Or is all the light relative anyway?

 

Should the different sections have white or black separation between them?

 

Am I over looking any important detail with running these tests?

 

 

Thanks!


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#2 Brian Drysdale

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Posted 18 June 2018 - 09:37 AM

You could look at the camera evaluation tests on CML. I gather exposure is more a stop adjustment on the lens than adding ND on the lights in those tests.


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#3 Macks Fiiod

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Posted 18 June 2018 - 09:51 AM

You could look at the camera evaluation tests on CML. I gather exposure is more a stop adjustment on the lens than adding ND on the lights in those tests.

I just checked that and they only seem to list new cameras. I have stuff pre 2012 to look at.


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#4 Brian Drysdale

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Posted 18 June 2018 - 01:47 PM

There are older cameras there like the Viper, F900, Silicon Imaging 2k etc


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#5 Bruce Greene

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Posted 18 June 2018 - 03:08 PM

The ND filter technique will work ok until you start to stack them up, then the errors of their accuracy will start to appear. 

 

Yes, place black behind the tube.  And try measuring the "patches" with a spot meter to see if your scale is accurate enough.  Don't be surprised to see color shifts as you stack the ND filters.

 

And also, the DR of the camera will be effected by the color temperature of the lamp.  From my experience, maximum DR might be at a color temperature of 4500k, but each camera might be different.  For practical reasons, conduct the test with "daylight" and "tungsten" lamps.

 

Also, the "base" ISO might not yield maximum DR.  So do the test at varying ISO settings as well.

 

Now that I think about this, I have a better idea from my film testing days.  I used to shoot movie film in my still camera for this test.  Instead of trying to capture the whole DR in one image, I photographed a white towel exposing from below maximum black to above maximum white.  I then placed the frame strip on a light table and looked at my new "DR ramp".  Why the towel?  The texture in the cloth helped to see where I lost visible detail.

 

How to do this with a digital camera?  Shoot all your images of the white towel by varying the exposure in the camera.  Then take one frame from each, crop it, and create your DR greyscale test ramp in video editing software such as Resolve.  This way you will not rely on the ND gels, you'll be able to see where you loose detail in the texture of the towel, and you'll be able to have 1/2 stop exposure changes rather than the full stop changes that the ND gels provide.  And you will also learn how to expose for your camera using a spot meter when you're actually shooting a movie with it!


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#6 Bruce Greene

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Posted 18 June 2018 - 03:16 PM

The ND filter technique will work ok until you start to stack them up, then the errors of their accuracy will start to appear. 

 

Yes, place black behind the tube.  And try measuring the "patches" with a spot meter to see if your scale is accurate enough.  Don't be surprised to see color shifts as you stack the ND filters.

 

And also, the DR of the camera will be effected by the color temperature of the lamp.  From my experience, maximum DR might be at a color temperature of 4500k, but each camera might be different.  For practical reasons, conduct the test with "daylight" and "tungsten" lamps.

 

Also, the "base" ISO might not yield maximum DR.  So do the test at varying ISO settings as well.

 

Now that I think about this, I have a better idea from my film testing days.  I used to shoot movie film in my still camera for this test.  Instead of trying to capture the whole DR in one image, I photographed a white towel exposing from below maximum black to above maximum white.  I then placed the frame strip on a light table and looked at my new "DR ramp".  Why the towel?  The texture in the cloth helped to see where I lost visible detail.

 

How to do this with a digital camera?  Shoot all your images of the white towel by varying the exposure in the camera.  Then take one frame from each, crop it, and create your DR greyscale test ramp in video editing software such as Resolve.  This way you will not rely on the ND gels, you'll be able to see where you loose detail in the texture of the towel, and you'll be able to have 1/2 stop exposure changes rather than the full stop changes that the ND gels provide.  And you will also learn how to expose for your camera using a spot meter when you're actually shooting a movie with it!

And, when you're evaluating this test, look at the waveform monitor in Reslove to see what the different camera settings do to the tone curve.  You'll be able to clearly see the difference between "video" "cinelike" and all the other choices.  Since you have older cameras also try the test with the "knee" function activated to see what happens to the curve with the knee applied.


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Willys Widgets

Technodolly

New Pro Video - New and Used Equipment

CineLab

Media Blackout - Custom Cables and AKS

FJS International, LLC

Glidecam

The Slider

Rig Wheels Passport

Metropolis Post

Wooden Camera

Aerial Filmworks

Gamma Ray Digital Inc

Ritter Battery

Tai Audio

CineTape

Broadcast Solutions Inc

Abel Cine

rebotnix Technologies