I'm not modern. In the era of curved sensors, light field cameras and super fast autofocusing I still love my ancient Helios-44 more any other lens.
This lens was released in 1951 in USSR as an "improved" clone of good old Carl Zeiss Biotar 2/58. Unfortunately it appeared to be worse than its "father": Helios was much less reliable, collected dust and sand, lacked good optical resolution. It seems, that the lens inherited only the look, and even its look was slightly changed since the beginning of production. Helios-44 wasn't good even on that time: Soviet professionals prefered Volna, Tair or any German optics.
Sounds bad? Yes. But what makes me leave my autofocus lens at home and take Helios-44 instead?
The miserable son of the great father is not that bad as it seems. Yes, it is not sharp enough (it's not sharp at all) and creaks when you focus, but it is still a great piece of glass and metal. It's very light and solid. If you manage to break Helios, you'll easily get a new one for $30 on eBay. The bokeh of Helilos-44 is exceptional: soft twisted circles on the background is a signature of this lens. Even the lack of detail does a good job: I don't need to photoshop skin pores, I just don't get them in the image!
Isn't it great? No.
Honestly, all these cons look very poor even for me.
The main and the only reason why I use it is that I have a lot of fun using Helios-44. Having fun is a 90% of success: you won't be able to make a good photo if you don't have any pleasure from your $3000 camera. Sometimes a cardboard box with a pin hole and old expired film gives more fun than any expensive digital Canon or Nikon. That's what happens to me with this old lens.
And there's no rational explanation for it.