The photo above was shot outdoors in full daylight.
The Speed Graphic shots were taken with a vintage lens from the 40s, and the RZ shots were taken with a UV filter over the lens. That is about all I can say. My references taken with the same camera on Portra and other films and the Polaroids came out just fine too at their proper ISO ratings.
If there is something wrong or skewed about my results, I'll be happy to have it pointed out to me. And, BTW, this is how I test my ISO 40 Ortho emulsion. Same cameras, meter and method. I have had 3 workshops with groups of students verify this ISO # with their own cameras - not mine, and also several private workshops that have gotten the same ISO 40 value for my home made emulsion here using my cameras.
My ISO 40 emulsion coated on paper is about ISO 100, another correct value as you gain about 1 stop when you coat a film emulsion on paper base due to back reflection. So, my film emulsion on paper is about 2 stops faster than the Ilford MGIV.
When used on-easel, my film emulsion is about 2 stops faster (or more) than Ilford which is a further point of reference.
I use Dektol 1:3 or Liquidol 1:9 for processing at 68 deg F for 1 minute.