Reco. letter from prof. with 5 months contact?

[Adip]

Hello,

I want two recommendation letters for MS in mechanical engineering. I am doing research with a professor for past 5 months. How is it effective to take letter from a professor with just 5 months of contact? Will letter be more effective if I take it from professor who knows me for 2-3 years ? I am confused in this regard. Please help me. Thanks

[ktel]

I don't think any of my recommenders knew me for more than a year. I didn't really start getting involved in projects until my last year