You chose a good object for this study, in some aspects simple, but in others quite challenging to photograph. Anything, which is reflective and/or transparent, is going to require quite a bit of thought and preparation. Looking at this submission as a set of thumbnails, you have really explored the glass bowl; looking at angles and height, in addition to and to complement the individual approach to each image. In addition, looking through the other exercises in your blog, you have spent some considerable time exploring the idea of light – natural and artificial – and the way that can impact on any image. Lighting plays such a vital role in the way an image can be captured, and it is no easy thing to control or master.
The use of a backlight, a black background, and that nicely controlled crescent of light on the ‘ground’ helps to define the shape of this glass bowl. The outline (rim) is well defined, although the glass is quite difficult to light in this way. I particularly like the inconsistency and variation in the light around the rim. As you say in your reflection, the act that the object is transparent means that the entire shape is rendered, rather than just the silhouette, bringing some sense of depth and multi-layered textures to the image.
The second, closer detail shot is very nice, capturing a real sense of the texture and feel of the piece. The use of a longer lens to create a greater depth of field and throw the background into soft focus complements and enhances the object. There is a lovely clarity about the colour and texture here, it looks, exactly I imagine, as the artist hoped, like something fluid and molten captured in time. I think you’re right about the square format, it really helps the composition.
Interestingly, because of the nature of the substance, and the way it has been cast/blown, the use of fill is probably redundant because the light from the key is captured and reflected in the glass. There is a good sense of the form of the object in both images, and while I’m not a great fan of monochrome conversions in digital work, the second image works well in establishing and defining the volume of the object. I might have favoured a slightly higher and oblique angle in the first (colour) image to get a three-dimensional feel of the bowl, but you have managed to capture the curving rim very well here. In the second image, the oblique positioning of the piece helps, although it needs to be either further away from the backdrop, or shot with a longer lens and lower stop to reduce the DOF and eliminate the creases in the cloth.
The textbooks are right about capturing texture, lights placed at acute angles will capture any roughness or blemishes and produce shadows, but this is tricky with glass because of the smooth surface. The texture in the bowl is mostly inside the material, although with the second image, there is a good sense of the ridges and waves. However, the material is nicely captured here, and there is a good sense of the feel of the object, its smoothness, the flowing surface. The shadows cast by the bowl are worth exploring – I like the pattern cast onto the ground in the second shot, it too, helps to define the nature of the object.
The use of a black and a white backdrop to explore the colour of the object is a good approach in these two images. The first, from above, is a strong and unusual angle, which makes the (already exotic) piece, look like some strange sea creature captured in shallow water. The colour here is good as the shadow level, and thus contrast is quite low and this renders the greens bright and clear. In the second image, your idea of backdrop and ground in black to crate a floating effect is very good; all elements of the object, shape, form, texture and colour are present here.
So, this is another well-considered and produced assignment, demonstrating both a high level of commitment to exploring lighting technique, and an excellent practical outcome. I think books about lighting techniques have their place, but there is no substitute for exploration and experimentation. But what I do know, is once we understand how to begin to control and manipulate light (and shade), both interior and exterior, then we really begin to understand the nature of photography. Always carry a reflector...