If i use captcha will i be able to stop the spam completely in my blog?

[dredgence]

i have a blog and the only user input is the commenting system, now i want to avoid the spam totally, which method will be wise to adopt? akismet way or captcha method.. my client doesnt mind his user entering few verification string to post comment, if i adopt it will i be able to completely control the spam if yes then could you please suggest few good and easy plugin like 4 digit , not the complex one. thank you