Stouffer - How to properly light and expose for?

[Ryan E. Walters]

So, I'm not really sure where to post this- If I have placed in the wrong place, please forgive me, and can someone move it to the correct place?

Anyway, I have a Stouffer chart and I am wondering what the standard practice / best practice is for lighting and exposing it. From what I've read online I gather that it is very crucial how I light and expose the chart, but I couldn't tell how I should be setting it up. Can someone enlighten me?

 

[Evangelos Achillopoulos]

First of all find a room that can be totally dark.

Then take a big rectangular flat surface that has a thickness of at least 8mm and is quite rigid, it can be from wood or from paper. The size should be 1.5m x 1.2m. in the center open a hole bigger than the chart by 3cm on every direction. Now paint the surface with a black mat paint or cover it with a black velvet.

Take Stouffer chart and put it in between of two black cardboards (1mm thick) in a way that only the steps are visible (make a hole on both sides) use glue or other adhesives to fix it, at the end you will have the chart mounted on a black cardboard that will be easily to move around without touching the Stouffer.

Mount the cardboard chart on the rectangular surface in a way that the cardboard will totally cover the hole and have the Stouffer in the center.

Put the rectangular surface in the dark room and make a light rig in the back that has the light totally diffused and even in all the range of the chart. The light should be strong enough to be clipping with F4 aperture on your camera.

The light should be measured with a spectrophotometer like X-Rite eye one pro with the help of spectral tools of Babelcolor CT&A www.babelcolor.com and it have to match the D32 for tungsten and D56 for daylight spectral range. A simple kelvin meter will not probably show a spike in green i.e. If you can use a tungsten light source properly diffused and just before the chart use a gelatin to make it daylight. Tungsten sources have the best spectral behavior.

It is crucial the light to have the correct spectral response and be totally diffused.

You have to cover the rig with black cloth in order the lighting rig not to lighten up the room. So while you measure the room should be dark as possible and the steps on the chart only to be visible. The lens should not have any other source of light around him.

Put the camera in with a wide lens like a 25mm in order to have full frame the Stouffer, expose in a way that the RAW file will have just clipped the most bright patch. is better to do few exposures with +/- 1 stop with 1/4 stop increments.

In this way you will have the ability to measure in both tungsten and daylight the measured camera. Remember when to export the image from the debayer tools to have linear light and use 16 bit Tiff.

This is the way I measure DR.

 

[Ryan E. Walters]

Brilliant- thanks for the detailed response, that is very helpful. And now I am off to start testing.