I bought the stouffer #T2115 - 21 at Fotoimpex, if you also buy some film shipping cost is atenuated... and shipping is registered and fast. IIRC they don't serve the 45 size.
https://www.fotoimpex.de/shop/system...che=1504277294
I prefer that #T2115 size, rather than the 45 size. It is perfect for film calibrations and I also scan it alongsize with a sheet, so I've a a precise reference for the densities in the sheet.
You can also buy an IT8.7/1 transparent calibration target ( Note IT8.7/2 is a reflective target), it has color and bw scales. You can find used ones at Ebay. (As you already have a calibrated strip...)
The #T2115 is more suitable for film calibrations, you cut film strips for that, saving money...
The "TP" of TP4x5-31 stands for "Transmission Projection", it is intended to be projected with a 4x5 enlarger to "establish exposure and processing adjustments and to determine the speed and contrast of photographic papers", they say.
For film calibration 1/2 steps are more desired. For paper measurements perhaps 1/3 steps may be desired. DMax it is the same (3.05D) in both cases, 31 steps and 21 steps.
Regards
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