Small Dilemma 20x or 2mm

[colinbm]

I have a Small Dilemma 20x or 2mm.
I can now do macro down to 20x, that is 1.8mm on a full frame sensor.
But 2mm on the sensor would make scaling measurements on the image easier.
Which do I chose ?

[Kai]

This is obviously a matter of taste - as long as the information is correct.
I like best a scale in the picture, e.g. 1 mm, divided into 10 divisions.
Are you sure your images cover exactly 1.8mm? If you stack them, there's bound to be a little cropping, right?

[colinbm]

@Kai Ha ha, exactly 1.8mm as far as I can ascertain, I need to find a very fine scale ruler. 
2mm is easier to establish with half & half of the divider on each side of the frame.
But now I have reached out to 1.5mm with a 0.5 division ruler.

[ulf]

4 minutes ago, colinbm said:

@Kai Ha ha, exactly 1.8mm as far as I can ascertain, I need to find a very fine scale ruler. 

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=stage+micrometer&_sacat=0

[colinbm]

Thanks Ulf

[Kai]

Of course, I didn't mean to use a real standard.
You can calibrate on it (such one like Ulf linked), the scale itself must be inserted digitally...

 

[colinbm]

Thanks Kai

[ulf]

Be aware of that precision calibration stage micrometer scales are made by depositing shiny but opaque chrome on the glass surface.

They are not printed black and are best visible with back illumination.

[Lou Jost]

Your two alternatives aren't mutually exclusive. You can adjust the focal length of the tube lens so that your 20x objective gives you 2mm on the sensor.

[colinbm]

Thanks Lou
I was wondering what was more presentable / preferable, To say the full frame is 2mm or the magnification is 20x ?

[Andy Perrin]

Colin, just put a scale bar in the picture (with photoshop or equivalent), that is probably the most useful to the viewer.