The role of macro lenses is to reduce distortion. Always a good idea in product photgrpahy. I’d check yourl ens to see how mcuh distrtio it produces. It would be one area a macro might be better. I haven’t seen distortion cahrt for that lens, spo I don’t know. Still soething to maybe look at.
The scheimpflug effect is reduced only with a tilt sift camera, a view camera. Some of us understand tilting the focal plane and film plane.
However, that’s not current practice as far as I know. For many doing product photography, they have a direct link to their editor for approval of images, or instructions for reshooting if necessary. I know of no tilt shift cameras capable of this kind of digital linking. SOme digital cameras having tilting lenses to tilt the focal plane, none that I know of have the matching tilting film plane, necessary for maximum control of the scheimpflug effect. It’s pretty much irrelevant. View cameras are not an efficient use of time.
I’m guessin like others, that 40mm is a nice focal length to work with. SO without addressing a specific problem, I’m not sure where to go with this one. To propose a solution, you have to understand the problem.
For product photography, DoF is important. Good fast glass is not necessary. There would be no advantage to going faster than ƒ2.8. As note above, ƒ4 would probably do.
What makes you think other lenses better than your current one actually exist? I find a difference of 200 lw/ph is barely noticeable in the final output. But it can cost a small fortune. It is increasingly rare when the top of the line lenses are more than 200 lw/ph better than the kit lenses. With computerized designs, many kit lenses will out perform older premium lenses. Product photography is usually not dependant on high resolution. The opposite may be true. Over sharpening may cause distracting unwanted detail. After all, your image will likely be so much reduced in size in the catalogue, and increase in resolution will be lost when the size is reduced. There’s no difference in my K-5 (16 MP) and K-1 (36 MP) omages reduced to 2160-3840 for my 4k TV. If you’re shooting for a 4k output, the K-5iis used is about $250. A K-1 ii about $2500… You can pay a lot of money for nothing if you don’t pay attention to what you actually need.
I’m tempted to recommend the Super Focus function in Topaz Photo AI. But, it’s till in it’s infacny and results are varied, sometimes bang on, sometimes a complete mess. And it really slows down your work flow.