> a decent diameter lens? The lens on my SOny thing is barely 1cm across.
And the "film" is also about 1cm.
Note that your eye, your reference for "nice image", opens only about 1mm-2mm.
With 2-inch (35mm) film you use a 2-inch long 1" or 1.5" wide lens.... mostly because you can.
When I was a boy I lugged 4x5 gear for my dad. Lens was 5" or 6" long, wasn't even an inch wide.
_Ratio_ of lens opening to length/width is one factor of Depth Of Field. Focus the woman's eyes but soften the hair and nose.
In most Product Photography you want maximum DoF, minimum lens opening. Depending on format and lens, f/8 to f/22. Which means sunlight if you want to hand-hold, or tripod. However with longer lenses (less foreshortening) you may not need huge DoF, f/4 can be fine.
I'm happy with an old Fuji S5000 and with a $140 Canon (which I got $5 used). Lighting and careful thought counts for more than glass or film.
> with diffucser.
Probably not big enough.
Sahib is suggesting "huge" light sources. Whole ceilings, or white "walls" right next to the object.
For smaller items, Meathands' pointer to a lightbox is great. Jewelry, trinkets.... whole cars if you build it big enough.
Greg's idea "near a window" is classic, even before photography.
http://www.kenrockwell.com/tech/product-photography.htm