Photographing glass - light 'quality'?

Question

I've read many articles on how to shoot clear glass objects. They seem to be very concerned with how you light it, but not so much how to determine the 'quality' of that light.

There also seems to be a large hole in the information as to what lens to choose, but I quickly determined 'think like a portrait' & went for 100mm.

I ran some quick tests to determine where my information was lacking as to lighting.

Assuming this type of image would be used to sell glasses via online stores I looked down the examples of a large prestige department store - John Lewis if you want some comparisons - but quickly realised there seems to be no 'golden rule'. There doesn't appear to even be a 'house style' that they follow; it appears that each brand submits its own pictures.

In the absence of any kind of house style, is there an objective or even subjective 'best approach'?
In fact, is there a 'best method', or is it up to the individual? Is this part of the decision-making process an 'art' or a 'craft'?

I honed it to three basic styles... these are just quick examples
[right-click, open in new tab for larger sizes]

1. Hard light
   Done by moving my white backdrop further away.
   

2. Soft light.
   Bringing the backdrop close - exposure needs tighter control so the backdrop doesn't appear in focus.
   

3. Specular light
   I brought one naked speedlight to 45° front left. Were this more than a quick experiment I would possibly have used a vertical softbox instead.
   

I feel each could have its place.
Overall I quite like the 'specular' but it requires that the background is not pure white, unless manually cut out in post.

Answer 1

It's hard to say which is the best approach because, as usual, it depends on what you're trying to convey. However, I think the book Light—Science & Magic: An Introduction to Photographic Lighting is a great source for learning lighting in general, and specifically for tips on how to light glass, how to highlight the borders, how to create intended reflections, etc.

My personal preference is to highlight the borders. For example if you want a white background you could use a white background that just covers the frame and and black background that surrounds the white background (and is not visible in the frame).

In the following example I used a dark background, and a white background outside the frame to highlight the borders:

And here is the lighting setup:
_{(source: staticflickr.com)}

Notice also that instead of a frontal bare flash for specular light I used paper strips to create softer and wider lights in both sides of the cup.