How can I measure a droplets contact angle without a setup?

I have to use a phone camera to replicate the Sessile drop analyzer, but there doesn't seem to be a standard to different parameters, such as how far away should my camera be from the droplet or how much liquid should I use for my droplets? Is it possible to get accurate results this way, and how should I go about it?




In 2010, Borguet *et al.* published in [*Journal of Chemical Education*, DOI: 10.1021/ed100468u](http://pubs.acs.org/doi/abs/10.1021/ed100468u) an intentionally simplified setup which may be useful as a reference. A Sony Cybershot camera was placed in front of a sample scrutinized under diffuse illumination:


[![enter image description here](https://i.stack.imgur.com/EyveW.png)](https://i.stack.imgur.com/EyveW.png)


The additional lens shown is focussed on the drop (both for water and $n$-hexadecane, the authors recommend a volume of $\pu{5 uL}$; focal length of the length used equals $\pu{50 mm}$):[![enter image description here](https://i.stack.imgur.com/yxh3a.png)](https://i.stack.imgur.com/yxh3a.png).


With photos recorded like this


[![enter image description here](https://i.stack.imgur.com/6DJqi.png)](https://i.stack.imgur.com/6DJqi.png)


the contact angle determination was performed with the [contact angle plugin](https://imagej.nih.gov/ij/plugins/contact-angle.html) of [imageJ](https://imagej.nih.gov/ij/). As [Fiji](http://fiji.sc/), it is open source, free ware, and java based/OS portable. To quote from their publication:



> 
> For each easurement, the user must choose two points to manually
>  define the baseline and three points along the drop profile (see
>  the supporting information that features a set of instructions
>  supplying all the details on the procedure used to make the
>  measurement). The program then fits the profile of the drop and
>  calculates the contact angle using the sphere approximation
>  or the ellipse approximation. In our study, the ellipse approximation gave consistent results for contact angles $> 40^\circ{}$. For
>  drops with contact angles $< 40^\circ{}$, the sphere approximation was
>  used.
> 
> 
> 


In comparison with reference data, the authors judge contact angles recorded as well as the subsequently calculated surface tensions as good enough for instruction / lab classes and research lab.


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