Topic: Kodak Super-XX Film Test

[Bryan]

A few months ago I picked up an unopened box of 4x5 Kodak Super-XX Pan Film dated September 1980.  The data sheet that was in the box listed it at ASA - 200.  I decided to do a test to determine what ASA would be best to use.  I figured that since it is 35 years old it would be around 12 or 25.  To test it I metered the shot at 100 ASA and came up with f/16 at 1/100.  I pulled the dark slide out 1 inch and took the shot.  I then proceeded to pull the dark slide out 1 inch at a time shooting at the same settings.  As you can see in the photos below there are 5 different exposures the darkest being f/16 at 1/100.  The next one is f/16 at 1/100 x 2 or 1/50 and so on.  This is where I get confused, does each one effectively reduce the ASA by half?  Lets say I decide to use the one in the center, f/16 at 1/100 x 3, would that be equivalent to an ASA of 25 or is 1/100x4 at ASA 25?  It seemed simple when I shot it but the more I think about it the more I think I could be wrong.  The math makes my head hurt and I know there are some on this forum that actually enjoy this stuff, your help is much appreciated. 

I scanned the negative on a light table with an OM-D E-M5 and reversed it with Photoshop Express.  The first one is just the image reversed and the second one is with adjustments.  I think 1/100x3 or 1/100x4 is about where I want to be but your opinions on that would be helpful.  I metered on the fence, the sun was out and the light didn't change during the 5 shots.  The negative was Semi-Stand developed in Rodinal 1-100 for 1 hour which is how I will likely be developing this film in the future.

[jharr]

1/100x4=1/25, so I would say that your effective iso is 25. Sunny 16 says shoot the inverse of the iso at f/16 in sunny conditions.

[Francois]

Yes it's a full stop per slice. As for the optimal result, it's hard to tell since we have no idea of the tonal relationship of the scene. A better test would be to take a shot of an evenly lit 18% gray card and set the scan so that the border is black. Then use the color picker to select the gray slice that would be closest to middle gray 50% in Photoshop or a value of 127 or thereabout.

[Bryan]

Thanks for clearing that up James and Francois, I think my head is still spinning after the discussion about senistometric density curves.  The reason I chose that shot, besides the convenience of my back yard, it has a variety of tones and shadows.  I will likely use 25 ASA for this film. 

[Francois]

I feel the optimal spot is probably somewhere between 25 and 50.
Looking at the shadows, the amount of detail visible will give you your answer.