AF problems on 50mm 1.4?

Started Dec 26, 2012 | Discussions thread
OP John Little Contributing Member • Posts: 520
Got the new 1.8 and it's great!

Well, I got my new 1.8 lens last night (despite the UPS driver who delivered it one street over from mine, to the house with the same house number). As soon as I opened the box, I noticed something different from the original lens: this one has an instruction sheet, which the original did not. That means that at least one person had already rejected the first lens and sent it back to the seller (minus its instruction sheet).

This lens is definitely better than the first. Because the first lens was so atrocious, the first thing I did was to set up on a tripod with a cable release and make a bunch of test shots. A lot of people say things like, “You’re not going to use the lens for taking pictures of little black lines on white surfaces so who cares?” The point is, if you know what the lens can do, then when your results are off you have a better idea if it’s you or the lens.

The point of the testing was to test AF accuracy, not sharpness, so I just used sharpness of 2 in DPP for everything, just to help me see where the sharpest area was. I used 3 different setups, at 3 different distances, in 3 different available-light situations. I bought the lens for head-shot portraits, so I tested from distances of 5 ft and closer. I made a total of 76 exposures and checked them in DPP at 100%, comparing the visually sharpest area to DPP’s little red square. I graded focus as either perfect, close, or bad. In total, I judged 51 of the shots to be either perfect or close; that’s 2/3 that are good. With the previous lens, the OOF shots far out-numbered the good ones.

Okay! Real life! I am *&^)*&!@(^%^ amazed! Hand-held shots at f1.8 & f2.0, 1/30 sec. by a tungsten lamp by the couch where my wife was sitting. Head shots, focusing on the eye. I took only 8 shots, bugging her while she was trying to watch TV. Of the 8, I threw 2 out because they were very obviously OOF, or I moved, or something. Of the other 6, viewing them at sharpness 2 in DPP, 3 of them were very sharp without anything else being done to them. They were great, and I was shocked! The other 3 needed minimal sharpening to get them more than sharp enough for a portrait.

I took dozens & dozens of shots of my wife with the previous lens and probably got ten that were sharp “enough” after being sharpened up, but they sure weren’t even close to "usable" at DPP sharpness 2, and they were shot at 1/250 and faster. I am so glad I sent that first lens back and swapped it out for this one.

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