I have taken a bunch of photos using a forensic bite mark scale; perfect size to put in photos with the study organism – fungi fruit bodies. It is a commonly used one that you can buy pretty cheaply (e.g. https://www.lociforensics.nl/products/crime-scene-documentation/rulers-photo-scales/abfo-no-2—bitemark-scale). It states in the info for this tool that the reflectance value is about 18, I would like to know if there is a way to double check this somehow? I will be calibrating these photos to extract CIELAB values. I can take RAW photos with this standard and the X-Rite ColorChecker Passport in the same photo, but I have no idea if it is possible to measure reflectance from this. Or do I need to ask around the departments and see if someone has a spectrometer I can use? If push comes to shove, can I use the value of 18 and then double check the photo output somehow? I am just made a bit unsure by the use of ‘about 18%’ in the product information.
Thanks for the fast answer! Great to know that I can measure it with the camera and the photos I already have – that will make life much easier. I will probably measure them anyway as although this data isn’t going to be used for other studies at the moment, I am hoping to put the values in a trait database for later use. I will post here the values I get for the two standards I have (two teams were using them) in case it is of use to anyone in the future.
Yes, they are a really handy design and good to have in field as they are pretty robust and the scale bars on them are excellent. A bit weird ordering something from a forensic lab that is normally used in police cases, but it does the job. In terms of difuseness, they seem pretty good – they are pretty matte and I can only get light reflecting off them if I hold at certain angles in direct sunlight, which is almost never the case for me as I work in shady forests (this may be a problem if you were working in grasslands or similar though). I think because they are designed to calibrate photos that are used as in evidence in court, they have to be to a pretty high level. Not as good as something like a Spectralon standard of course, but the field work budget didn’t stretch that far 🙂
Thanks again, Sam