Back in the 1980's, when dinosaurs walked the face of the earth, Popular Photography used to do camera and lens testing on 35mm equipment. If I remember their results correctly, the 50mm f1.8 was given a better score than the 50mm f1.4. These tests were generally based on sharpness, distortion and contrast. I certainly cannot argue with the general reputation of the 50mm f1.8 being a fine performer, but for my uses, the 50mm f1.4 is also a fine performer. I will try and give you some of my personal observations.
Zuiko 50mm f1.8 Auto-S
Olympus made a lot of these. They were cheap to produce. Optical construction is six elements in four groups. This lens went through a series of revisions and there are probably five different versions. On their earliest lenses, Olympus used a thin silver accent at the front of the aperture ring and at the front of the filter threads. These are called Silvernose. Earlier versions were single coated and later versions are multi-coated. The single coated versions were labeled F.Zuiko (there are six elements and 'F' is the sixth letter of the alphabet). The last revision has the following markings on the front of the lens: "OLYMPUS OM-SYSTEM ZUIKO AUTO-S 50mm 1:1,8 made in Japan". Filter size is 49mm.
The 50mm f 1.8 Zuiko has the reputation of sharpness and very low distortion. I have four of these at present ranging from a silvernose F.Zuiko to a "made in Japan" with serial #3632896. I don't use the 50mm f1.8 Zuiko all that much, but when I do, it always makes a sharp and contrasty image, if I do my part. At f1.8, these are quite sharp.
Zuiko 50mm f1.4 Auto-S
The 50mm f1.4 Zuiko went through at least four revisions. Optical construction is seven elements in six groups. Filter size is 49mm.
This lens is the red haired step-child of the Zuikos. The camera magazines that you mentioned earlier found a distortion and contrast problem with their test lens, and the 50mm f1.4 has never shaken the reputation of being a dud. I own three 50mm f1.4 Zuikos. I have a Silvernose G.Zuiko and and two of the last revision. I have two bodies that always have a 50mm f1.4 mounted. These can be a little soft wide open but I have no problems with distortion or contrast. I cannot help but think that the lens testers got a miss-alligned lens to test. The highest serial number that I have seen is 1153xxx. If you can judge by serial numbers, Olympus sold well over one million copies of this lens and sales of this lens was roughly one copy for every three or four of the 50mm f1.8. This lens originally sold for roughly 175% of the price of the 50mm f1.8, so my take on this lens is that buyers did not shun the 50mm f 1.4.
G.Zuiko 55mm f1.2 Auto-S
I have two copies of the 55mm f1.2, one is a silvernose and the other is all black. Both are single coated. As far as I can tell, this lens was discontinued around 1981 when Olympus went to multi-coating on all lenses and it was replaced by the 50mm f1.2 Zuiko. These can be soft wide open and the depth of field is quite shallow. It can be difficult to accurately focus wide open in low light especially when the subject is close to the camera. The up-side is that you get a full stop more light than the 50mm f1.8. I don't own nor have I ever handled a 50mm f1.2 Zuiko. These take 55mm filters.
Zuiko 50mm f2.0 Auto-Macro
This lens replaced the 50mm f 3.5 Macro and it employs a complex optical formula of nine elements in seven groups and it has floating element design to focus down to 1/2 life size. Filter size is 55mm. If you are into pure distortion free performance, buy one of these. You will have to pay a premium for the performance.
I have a couple of comments to make before I am done. I always use a lens hood. The benefits are better contrast and reduced lens flair. The best money that you can spend is to get and use a lens hood. I would also suggest that if the 50mm focal length is for you, get several different copies of lenses that interest you and keep the 'best' ones.
Zuiko 50/1.8, six elements in four groups; Zuiko 50/1.4 seven elements in six groups. So, from the standpoint of contrast and flare control the 1.8 will perform better than the 1.4 because it has fewer internal surfaces and smaller diameter elements - 1.8 has six internal surfaces, the 1.4 has ten.
All other things being equal, the slower lens will have greater apparent sharpness-"crispness" if you will.
From that I'm wondering if Olympus were following similar logic to Pentax at the time.
Pentax made a 55mm f1.8 and then a 50mm f1.7 as the "standard" lens with a 50mm f1.4 as the more expensive model. The slightly slower lenses were designed for ultimate sharpness and an ability to tolerate optical abuse - cheap teleconverters, filters, extension tubes, etc.
The f1.4 was designed for speed. It's slightly softer wide open but sharpens when stopped down. The suggestion is that it was intended for photojournalists rather than the serious amateur market. My experience is that at f1.4 the DOF is a knife-edge and yes, it's not particularly sharp. But as I said earlier, in the real world a soft image is better than no image if you can't use a slower shutter speed or faster film.
I have examples of all three and use them more-or-less interchangeably, my only consideration is how much risk there is of damage. If it's likely to get covered in spray or might get stolen I'll use the "disposable" one of the 50/1.7s (so called as I've already had it apart once to clean fungus out and I'm not worried about taking it apart again if it got, say, a drink spilled over it). Other than that it depends on the camera. The 55mm tends to stay on the KX it came with, the 50/1.4 migrates. One of my MXs and one of my MEs tend to hang onto the 50/1.7s they came with.
I have used a few variations of each type of lens, I have two of them on my desk now. My favorites are the 50/1.8, and the 50/1.2. The 50/1.8 is my favorite "all-around" lens, I use the 55/1.2 for shooting wide open at near subjects. The 55/1.2 gives dreamy results when shooting flowers, plants, or insects.
Thank you very much...
I don't speak and I don't understand at 100% english leanguage so please be patient with me
although I know it is not easy with my "stupid" questions...
I explaine a little:i haven't a lot of money...i can't buy both lens,unfortunarely.I must buy only zuiko 50 mm.
I need a excelent 50 mm,it isn't important at all the l the brightness of the glass. I don't use 1.4 or 1.8 diaphragms never so the brightness isn't an important feature at all.
I'm searching for a Zuiko 50 lens with sharpness,acutance,ecc...ecc...not with hight brightness level!
It seems that the 1.8 is better at this respect.
Is it correct?...
The 50 1.4 Zuiko that I could buy is the "OM-SYSTEM G.ZUIKO AUTO-S 1.4",while in this moment i don't remember at all which was the correct 1.8 model that I could buy...
So tecnically any 50 1.8 Zuiko lens,if I understanding correctly,is better (a part the brightness that it's not an important feature for me) than the G.Zuiko AUTO-S 1.4 50mm lens.
Is it correct?...in this case I prefer to buy the 1.8 50 mm Zuiko.
So do you think that this is the right choice for me?
I repeat, I'm sorry if I'm burdening us,but I haven't money at the moment and I've to do the right choice.In this case I haven't the possibility to experiment,to make comparisons...I must buy the right 50 mm Zuiko lens.
Please,for the last time,give me an opinion,Itrust you.
thanks for you patience.
Buy the one with the cleanest glass. That makes more difference than anything else.
I have 8 of the 1.8 and 3 of the 1.4
Cleanliness is Godliness.