Yongnuo recently released a 50mm F1.8 auto focus lens to compete with the very popular Canon version. The Canon 50mm F1.8 is already considered a bargain lens, so with the Yongnuo coming in at half the already bargain basement price, can it possibly perform equally or even better? Tony Northrup put together a fantastic and comprehensive video that pits these two lenses side by side in a comparison that will answer all your questions.
I think you also have to take into account the QC of the companies in question. I'm sure Canon is a bit more stringent with the consistency of their product quality than Yongnuo is, much like with all third party companies.
I'd like to see a comparison between three copies of the Yongnuo (since it's so cheap) to see if the lens is really that soft or if that copy paired with that camera is that soft.
I have to micro-adjust roughly 100% of my canon lenses in camera to make autofocus usable. 85 1.8 / 35 2 / 50 1.4 and 50 1.8.
I dont have much to compare with but i dont hold canons quality control very high.
I see people call the "you get what you pay for" every time YN releases something but personally i think their product line consists of excellent products. Especially their flashes and triggers.
That's normal. Most lenses require a little bit of micro-adjustment unless you get really lucky and get a lens/camera combo whose assembly line nuances match perfectly. It doesn't mean that Canon is lazy, nor does it mean that the lens itself is defective.
And besides that, I'm not talking about inherent autofocus accuracy that can be corrected (key words). I'm referring to the sharpness of the lens at critical focus.
Unless those lenses are incapable of focusing to a certain point or are blurry even after micro-adjustments, chances are your issue is just a common issue with any manufacturing process, since QC is not for making sure EVERY lens is perfect, but instead for making sure the lenses are within certain ranges.
Third parties don't seem to be as diligent in their QC as the big brands who charge top dollar.
I would imagine the lens-to-lens variance may be great with the Yongnuo, a first look a while back at Petapixel showed the Yongnuo optically a little better:
The AF issues Tony had here may well differ from lens to lens as well.
I find it rather odd that Yongnuo has decided to sell this lens to begin with, to the point of cloning it visually. That they're trying to out-cheap what is already a fairly cheap lens is weird too. The whole thing is really rather strange to me.
I thought the exact same thing. By the time I ordered a copy to test, the initial glowing reviews had caused a two-month backlog. When I finally got mine, I was really surprised that the quality didn't match that of the first reviews. That inconsistency caused me to triple-check everything.
Like you, I conclude that it's a manufacturing problem more than a design problem. From my conversations with different lens manufacturers, it sounds like quality control is the single hardest part of the process. They were probably more meticulous for the first batch and got sloppy to increase production and meet demand.
Another strike against the Yongnuo is that you can only buy it directly from China through ebay (currently), so returns and exchanges are really difficult. While shipping items from China is cheap thanks to the government-subsidized e-Packet, returning items can be expensive, and probably not worth it for a lens like this.
I just wish someone woukd make a comparatively cheap 35mm or even 24mm prime so every beginner wouldnt start out with an 85mm equivalent, which is a difficult walk-around lens.
Canon has the $150 24mm f/2.8 pancake, but it's only for crop cameras. :(
Still, if you're on a beginner with a beginner camera on a very low budget and need a lens that is a medium wide angle then that's about the best one...for Canon anyways.