Focus issues with Nikon 35mm f1.8 lens.

[trs0722]

Hi everyone. While this lens can be great and sharp on some images, I sometimes get soft pictures with others using my D5100. Hoping others can chime in or offer advice. I know that with f stops between 1.8 and 2.8 the plane of focus is very small. So if I'm shooting 2 kids and one kid is behind the other, I expect one to be softer than the other. So, I try to keep my f stop lower like 5.6 or 6.3 or go lower if I'm only shooting one kid.

I recently took pics at 2.8 and 5.6 and both kids' faces were soft. For the f2.8 shot, they were nearly on the same plane and my shutter speed was ok I think (1/200). I did focus somewhere right between them if not on one of their eyes (from what I recall). As you see, neither of their faces are sharp.

For the f5.6 shot, my shutter speed was slower (1/125) but I don't think that was the issue. I've gotten similar results with faster speeds. The kids were on different planes but I figured f5.6 would be ok. Again, neither face was sharp. I believe I focused on my son's face and even his is not in focus.

I'm concerned about a focusing issue with my lens...it's still under warranty until December so I gotta act soon if I want to send it back. Or maybe it's operator error.

Both pictures are right out of camera with only some minor sharpening and lens correction applied by Lightroom on import. Thanks!

 

[BoneDoc]

The most important thing to get perfect focus is to change the focus point to center point AF. Then focus EXACTLY ON THE EYE. The eye have it: if they're in focus, then everything else in focus. If they're not, then nothing is in focus. So, if your child is off center, then focus / recompose your shot.

Hope that helps .

Josh

 

[trs0722]

Thanks. Yup, usually put the point (usually use the center focus point on view finder) between the eyes. Been using back button focus lock too...has been a big help.

 

[Apple fanboy]

I was reading on dpreview about a different Nikon Lens they were testing (70-200 mm 2.8) and they said they had to try three lenses before they got a good one. If you are just photographing the one child, how does the focus look then? Might be easier to test it on something that doesn't move so much and see how you get on.

 

[ChrisA]

Line up some objects with fine detail on them and use a tape measure from sensor plan to subject.
Check inside the NEF file what distance the camera focused on.

If you are measuring lens sharpness don't measure autofocus at the same time. Measure one and then the other. Place the camera on a tripod and use the self timer so your hand does not shake the camera. Focus manually first to verify the lens CAN make a sharp image. Note where you focussed the lens then let the AF try and focus and see if the two of you agree.

It looks like either this lens is focusing in front of both subjects or it is simply a soft lens. So do some manual focused tripod shots. DOn't change the setup them do some AF shots and compare.


a 35mm lens has a pretty reasonable DOF at your distance, 3 or 4 inches at least. That is enough to capture the entire face. A longer lens might not get the nose and eyes in focus but the 35 has plenty of DOF

 

[trs0722]

I was reading on dpreview about a different Nikon Lens they were testing (70-200 mm 2.8) and they said they had to try three lenses before they got a good one. If you are just photographing the one child, how does the focus look then? Might be easier to test it on something that doesn't move so much and see how you get on.

Yeah, and that's an expensive lens!

I've gotten some great sharp pics from this lens with both solo and multiple subjects but it is really hit or miss. I took some more of just my son yesterday and the same thing: some really sharp and others soft. Many had really fast shutter speeds. I'm not a professional but am pretty sure it's not the camera or me. I've also been shooting a lot lately with the 55mm-200mm and have gotten way more sharp keepers than with the 35mm. May just send it to Nikon for them to figure it out.

 

[puckhead193]

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I'm concerned about a focusing issue with my lens...it's still under warranty until December so I gotta act soon if I want to send it back. Or maybe it's operator error.

Why waste time and not send that back to nikon right away? Do you need the lens for something specific?

 

[El Cabong]

You could try shooting a planar subject at an angle (e.g. measuring tape, http://www.photozone.de/nikon--nikkor-aps-c-lens-tests/628-nikkor3518dx?start=1, scroll to bottom). This makes it easier to determine exactly where the lens is focused. I had to do this with my D800 to figure out that it had a left autofocus sensor defect. Take multiple shots, using different focus areas, to determine whether something is off with your autofocus. If it focuses on the wrong spot consistently, the lens might have a back/front focusing issue. Since the D5100 doesn't have the AF Fine Tune function, the only way to correct this would be to service the lens.

 

[initialsBB]

Looking at the EXIF data in your photos it says "subject distance range unknown", whereas my D5000 gives me a distance value with auto-focus... Could very well be something wrong with the lens, so contact Nikon.