50mm f/1.8 focusing issue

Hello POTN.

So, first off, my camera *was* on a sturdy tripod when these samples were shot. The first was shot at f/8, ISO1600 for 30 seconds. The second was shot at f/2.0, ISO800 for 30 seconds. Results of f/2.0 were very similar at f/2.8. The issue pretty much resolved at f/4. Manually focused. Focus was not different in either image.

@ f/2.8:

quadwing wrote in post #17110792
Hello POTN.

So, first off, my camera *was* on a sturdy tripod when these samples were shot. The first was shot at f/8, ISO1600 for 30 seconds. The second was shot at f/2.0, ISO800 for 30 seconds. Results of f/2.0 were very similar at f/2.8. The issue pretty much resolved at f/4. Manually focused. Focus was not different in either image.

Basically, there's a bit of a "doubled" or "ghost" image of whatever I'm taking a photo of at wider apertures. It's particularly an issue when subjects are further away. It's really, really obnoxious. It's not motion blur, for certain. I'm thinking it's a mechanical issue. I haven't dropped the lens or anything, and it hasn't sustained any damage. There is, (and it's always been this way) however, a weird amount of "resistance" when you turn the focusing wheel to the closest. Beyond that, the "ghosting" is a relatively new issue. Anyone have similar issues?

Hi , The conditions seem all wrong for testing to me , try doing it where youre not having to do 30 second exposures at high ISOs at night.

Try in good daylight - F/2 on a 50mm lens for a landscape shot , not ideal for testing focus

The 50/1.8 has a known issue with (presumably) residual spherical aberration causing focus issues wide open. It doesn't manifest itself in all shots, but is hard to deal with when it does. There's a nice article HERE about it.

Sometimes switching to a different focus point (or focusing with an artificial aid) will help. You're trying to focus in conditions that are very demanding for this inexpensive lens; but you can usually work around them.

*Jayrou wrote in post #17111159
Hi , The conditions seem all wrong for testing to me , try doing it where youre not having to do 30 second exposures at high ISOs at night.

Try in good daylight - F/2 on a 50mm lens for a landscape shot , not ideal for testing focus

Agreed.

there's now way you can say for sure that it's not motion blur, if you're shooting at 30 sec....shoot at a faster shutter to rule out motion blur...also if you MF the shots, then there's not an AF issue with the lens...where did you focus anyways, if you focused closer it could've just been the DOF expanding to cover the farther subjects...

I've had 3 copies of the 50 1.8 II. I used it on a 500D, 60D, 5D, and 6D. I couldn't get any of them to focus consistently on any of the bodies. I tested them on a tripod, wide-open, daylight, high-contrast subject at 50x focal length. The BEST I could get was about 80% keepers on the 6D. In fluorescent or incandescent light, the keepers dropped below 50% on the 6D. On the 60D it was just over 10%. In poor light, I got a fair amount of OOF shots at f/8.

I've just purchased a 50 1.4. I know it isn't sharp at f/1.4. I just hope it can nail focus at f/2.0-2.5.

GregDunn wrote in post #17111223
The 50/1.8 has a known issue with (presumably) residual spherical aberration causing focus issues wide open. It doesn't manifest itself in all shots, but is hard to deal with when it does. There's a nice article HERE about it.

Sometimes switching to a different focus point (or focusing with an artificial aid) will help. You're trying to focus in conditions that are very demanding for this inexpensive lens; but you can usually work around them.

To the best of my knowledge, residual spherical aberrations don't show up wide open. Their primary effect is to move the focus point when narrower apertures are used. The effect is usually worse at really close focus distances. I believe the 17-55 and 24-70 f/4 suffer from this. I believe 98% (guess) of people who own these lenses never notice it.

GeoKras1989 wrote in post #17112443
I've just purchased a 50 1.4. I know it isn't sharp at f/1.4. I just hope it can nail focus at f/2.0-2.5.

Yes it is.. It just take a bit of care and practice.

yogestee wrote in post #17112758
Yes it is.. It just take a bit of care and practice.

I hope so. I have no problems with the 35 IS or 100 2. The 50 1.8 just didn't work for me, though. I should have the 1.4 in a few days.

You guys have high expectations for a $120 lens I agree with DreDaze. You can't base anything on a 30 sec exposure. The testing conditions are so far from ideal, it's a waste of time really.

I fixed it!

There indeed was a focusing issue. Rather, an issue with the barrel of the lens. It was a little misaligned--it was tilting down for some reason. I turned the focusing ring until I exposed the lens barrel, and then pulled up on it kind of hard.. Went back into place. It's now very, very sharp again!

quadwing wrote in post #17113115
I fixed it!

There indeed was a focusing issue. Rather, an issue with the barrel of the lens. It was a little misaligned--it was tilting down for some reason. I turned the focusing ring until I exposed the lens barrel, and then pulled up on it kind of hard.. Went back into place. It's now very, very sharp again!

Sounds like maybe you dropped it?

Aressem wrote in post #17113249
Sounds like maybe you dropped it?

Those crappers do that out of the box.

Aressem wrote in post #17113249
Sounds like maybe you dropped it?

Nope! Only ever dropped one lens in my life.

Mike Deep wrote in post #17113257
Those crappers do that out of the box.

Hah! Yeah, pretty much.