You are showing some very nice sketches here.
For me, the 1st sketch of your 1st and 3rd latest post are the best ones.
Thanks for scanning, too. Investing in a printer + ADF scanner is no luxury.
I like how some of the ellipses are slightly off - it brings a cartoonesque quality, however for product design sketches I prefer them to be as accurate as possible. If you struggle, go back to drawing or visualizing a circumscribed square and the axes in perspective first.
Your linework is good. I am starting to see more consistency and style. You can still work on materials, colors and shading and it is a good step that you started developing more in-depth treating one product. See if you can do some research and make this a serious design exercise. You can focus for example on form and interaction of system cameras, which are slowly taking over the DSLR market but are still criticized of being too large and not user friendly in form factor.