I will catch up with your post in a sec Christine.
This will be a 2 part post to stay within image download limits.
2 pics attatched here.
Pic 1 deals with selection of the bowl. First row shows my prototype bowl on the X to show relative position of standard hotshoe mounted flash, and on D100 to show relative position of pop-up flash. Rows 2 and 3 are my Sunday purchases from Morrisons. Centre bowl is a 220mm mixing bowl cost £0:68, and right hand is a food storage container for £0:99.
Looking at these the thingst work out are : Potential subject choice, and therefore lens to subject distance and then pop-up or main flash gun. If pop-up then 220mm becomes a minimum diameter unless a cowl, as in my yesterdays post is also made, to deflect the flash beam downwards. Bowl style will be affected by lens to subject distance.
Pic 2 is to show two other considerations. 1) Lens hood. A lenshood that protrudes beyond the light source inside the bowl is an absolute essential. I taped two together for mine, but I could have used a bit of drain pipe. For use the outside of the hood needs to be wrapped in kitchen foil to assist light spread in the bowl. 2) Mounting. Consider how you will mount the bowl to the lens. I have a number of 52mm screw fit hoods, so for the inside I taped 2 hoods together and then screwed another from the outside of the bowl, allowing me to mount using the filter thread. If you have a Cokin filter holder then the adator ring can be used for the bowl to lens mount. These are available as an accessory but cost about £4:50. If the pop-up route is chosen then this can be taped to the outside of the bowl ( electrical tape or gaffer tape, NOT masking tape ). If a seperate flash unit is to be used the mounting of this would need to be more secure to carry the weight of the flashgun. So possibly drilled and held by screws.
Part 2 tomorrow
Don