Photographic reference scale

Some time ago I wondered if my observations were lacking a scale so I made a small reference inspired in the forensic ones and wanted to share it. The size is small enough to carry in most phone cases (10x5cm). I use it to measure fishes, small insects and under a petri dish for background. You can dowload it here or here ready to print.
What are your thoughts? Do you find it usefull?


A scale is good. But in some areas it will not be always obvious and this should also include mm., cm, lines or inches.


This does look very useful, thanks for sharing! May I also recommend the Life to Scale project? :)


After printing, compare to a real ruler to make sure it came out at the correct size.


Good job! I think it’s great that you created a custom scale. Is it paper with lamination? In cases like a petri dish, where scale dimensions cannot be inferred from the ruler marks, maybe adding a note stating that grid has 5 mm spacing would be helpful?

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Thankfully, if the markings are visible on the ruler edge, it’s easy to infer the scale.

If there are 10 divisions (spaces between dark marks) between major marks, it’s a metric/mm ruler 99.9% of the time, whereas if there are 2, 4, 8, 16, 32, etc. divisions it’s imperial/inches.

Still waiting for that 0.1% observer who carries around an imperial machinists ruler that divides inches into 10ths, that would be confusing for sure!

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