While I agree with many of the comments suggesting the 1.4....it is the hyperbole that really cracks me up. Example...above: "vastly better"....and how in the world is a 1.8 "nearly useless" in very low light??!?!?!? (Bites tongue)
Not a word of hyperbole in my original post. I find the 50/1.8mkII to be virtually useless in very low light, because the damn thing can't focus. On manual focus, it's fine; it'll produce good images. But AF performance on this lens is crap, especially when compared with the 50/1.4, which doesn't hunt nearly as much, and locks on quickly and accurately in all but the dimmest of light.
The 1.4 is simply better. That's not to say that the 1.8 is worthless; it's just that the 50/1.4 can be picked up used for so little (mid-$200s on Fred Miranda), that it makes no sense to spend $100 to get a lens with obvious deficiencies. If the 1.8 is all you can afford, then go for it; I still have one in my bag and it takes pictures that are head and shoulders above most kit lenses. But the 1.4 is, I'm sorry to say, "vastly better".
Don't sigh; it's just a lens. Nothing serious.
The OP asked if there is a "BIG" difference between the two lens..noting the 1.4 costs 3x more $$.
The value of a lens is not cost-dependent. The 5DmkII is a better camera than the XSi, for example; sure, it costs 5 times the price, but that's not the point. Whether the cost difference is worth it FOR YOU is a different concern, but there is a BIG difference between the 1.8 and 1.4, no matter what the price. And low light AF is a huge part of that difference.
I think, for the intended uses, the answer is still..."no". Is the 1.4 3x better than the 1.8? Not even remotely.
Sooooo not the point. To use my above example, is the 5dmkII 5x better than the XSi? How do you even quantify "X-times better"? If the features of a product are necessary for you, then you spend the money.
I'll give you another example: the 85/1.8 is a wicked lens, and costs $350ish. The 85/1.2L is better lens, and costs 4-5 times the price. Is the extra stop of light worth the cost? Is the MUCH shallower DOF worth the cost? Is the better bokeh worth the cost?
The answer to all of these questions is: maybe. If you need an extra stop of light, shallower DOF, orthe best bokeh you can buy, the answer is yes. If not, the answer is no. Can the 85/1.8 take amazing shots? Sure it can, but it cannot do all the things the 1.2L can do, and the 1.2L will be worth the money to some people.
And I think the difference between the 50/1.8 and the 50/1.4 is far bigger than the 85/1.8 vs. 85/1.2L example. It's a huge difference, especially when you're shooting in low light and getting 10% keepers because the 1.8 can't focus on anything.
If *I* had to put a percentage value on it, I would say the 1.4 is 30% better at the most...considering all factors such as build quality, AF, etc. If quiet focusing and built like a tank aren't important to you or *needed*, then far less.
Again, this is totally context-dependent. If the extra features of the 1.4 are necessary for you, then the difference in cost is worth it (and let's not kid ourselves, the 1.4 is still a very cheap lens...we're only having this discussion because the 1.8 is insanely cheap). For some people, the 50/1.2L is the only way to go; is THAT lens worth the cost?
So..OP...is a 30% improvement worth 3x the price to you? There's no right or wrong answer imo. For my uses, the 1.4 would be worth it, but I need a lens that can take a beating in travel and harsh conditions, focus as fast and quietly as possible etc, etc. I need to sell photographs(!) in a competitive market...plus I can write it off my taxes.
Exactly. Everyone needs to decide for him or herself what lens is "enough". For me, the 1.8 is not good enough because it is severely crippled for one of the main things you buy a fast prime for; low-light shooting. It gives nice shallow DOF, and for portrait photography on a budget with a 1.6x crop body, it could be fine. But for those who want big apertures for low light, the 1.4 is better.
Just to be clear, I'm not suggesting the 1.4 is a mistake by any means....but imo, you don't *need* it.
Seems to *me*, the best path is to get the 1.8...maybe used...or rent one... and see if you find its results and performance adequate for your needs. If not, sell the 1.8 and try the 1.4. Blessedly, we're not talking about a $1600 lens investment.
Agreed. Rent before you buy. Put the 1.8 through its paces, and see if it's enough lens for you. I'm not advocating overbuying; I'm advocating buying the right lens.
100% agreed.