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Lens I bought that should be very sharp is very soft. Why?
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PostPosted: Fri Dec 29, 2017 5:39 pm    Post subject: Lens I bought that should be very sharp is very soft. Why? Reply with quote

Hi. I just bought Nikon 55mm f/2.8 AF MICRO-NIKKOR. Ken Rockwell says its probably Nikon's sharpest lens (http://www.kenrockwell.com/nikon/55af.htm) and the sample images I saw on the internet are extremely sharp. However, the lens I bought is extremely soft. Its actually the less sharpest lens I had (even my cheap kit lens is much sharper). I have Nikon D3300. Where could be the problem? Do you think there is something wrong about this lens or am I doing something wrong? (Of course, I am focusing manually)
I try to upload some images tommorrow.


PostPosted: Fri Dec 29, 2017 8:12 pm    Post subject: Reply with quote

This lens should be very sharp indeed.

Just a few questions: do you have experience with manual lenses (or AF-lenses that you use manually)? Do you have other ones and are you familiar with working with them on you camera?
If the answer to those questons is yes: do you see any signs on the lens or do you have any indications that it could have been opened?
(Scratches around the screws on the back for example or parts with slack on them? etcetera..)
As I am thinking that a possible reason could be that the lens been taken apart (for whatever reason) and put together in a wrong way.

So, all possible information you can give about this lens regarding the functioning and even the appearance could be helpfull.


PostPosted: Fri Dec 29, 2017 8:48 pm    Post subject: Reply with quote

Lucse wrote:
This lens should be very sharp indeed.

Just a few questions: do you have experience with manual lenses (or AF-lenses that you use manually)? Do you have other ones and are you familiar with working with them on you camera?
If the answer to those questons is yes: do you see any signs on the lens or do you have any indications that it could have been opened?
(Scratches around the screws on the back for example or parts with slack on them? etcetera..)
As I am thinking that a possible reason could be that the lens been taken apart (for whatever reason) and put together in a wrong way.

So, all possible information you can give about this lens regarding the functioning and even the appearance could be helpfull.


Based on what little we know this would be my guess.

Another possibility would be a haze on an internal element. Shine a bright light through it and look for a hazed element. The bright light is critical as often you can't detect the haze in normal daylight.


PostPosted: Fri Dec 29, 2017 10:13 pm    Post subject: Reply with quote

The lens looks ok outside, but the image looks hazy. I am not sure if I can recognize the haze on the lens, but I tried the flashlight test and didnt see anything weird (only little bit of dust).

Here are some images I shot today:

1/160, f4, ISO 100, tripod, manual focus with zoomed in live view, 100% crop



1/200, f8, ISO 100, tripod, manual focus with zoomed in live view, shutter release, 100% crop:


PostPosted: Fri Dec 29, 2017 10:28 pm    Post subject: Reply with quote

I manual focus all the time, so I have some experience with it. This is my first vintage AF lens. I locked the lens aperture ring at minimum aperture and I controled the aperture in camera. It works ok. But that probably is not the problem.


PostPosted: Fri Dec 29, 2017 10:56 pm    Post subject: Reply with quote

See how it performs in auto focus...


PostPosted: Fri Dec 29, 2017 11:24 pm    Post subject: Reply with quote

I have Nikon D3300 which doesnt have built-in focus motor, so I cant try AF. The focus throw is extremely short, maybe AF it could perform better?


PostPosted: Fri Dec 29, 2017 11:44 pm    Post subject: Reply with quote

I tried different apertures (f/8 is rather ok, but still worse than my kit lens, f/3.5 is just out of focus, even when from a bigger distance).
Is this ok?

f/8



f/5.6


f/4.5


f/3.5
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PostPosted: Sat Dec 30, 2017 12:58 am    Post subject: Reply with quote

I'm guessing that lens should be way sharper than that even wide open (I don't own that particular lens). Do you have a rail? I like to focus as close as possible with the focus ring then zoom in as far as possible on the focus point and use the rail for micro adjustments. If you can't get a good sharp image that way the lens is definitely flawed in some way.


PostPosted: Sat Dec 30, 2017 2:58 am    Post subject: Reply with quote

Any decent modern lens should be sharper than that wide open.
I suspect a problem with element spacing or suchlike.

One good test for spacing issues, etc. is whether infinity is correct.
See if you can get infinity as marked.

Another test, to remove the possibility of missed focus, is to shoot a detailed surface (such as a tape measure or meter stick) at an angle to capture the whole DOF, from foreground to background. If nothing at all is sharp then you have a defective lens.

If some unexpected zone actually is sharp you may have a focus calibration problem with your camera body.


PostPosted: Sat Dec 30, 2017 3:00 am    Post subject: Reply with quote

Should be sharper than that. Rattle? Some internal adjustment needed?


PostPosted: Sat Dec 30, 2017 11:41 am    Post subject: Reply with quote

luisalegria wrote:
Any decent modern lens should be sharper than that wide open.
I suspect a problem with element spacing or suchlike.

One good test for spacing issues, etc. is whether infinity is correct.
See if you can get infinity as marked.

Another test, to remove the possibility of missed focus, is to shoot a detailed surface (such as a tape measure or meter stick) at an angle to capture the whole DOF, from foreground to background. If nothing at all is sharp then you have a defective lens.

If some unexpected zone actually is sharp you may have a focus calibration problem with your camera body.


f/5.6


f/3.5


PostPosted: Sat Dec 30, 2017 1:57 pm    Post subject: Reply with quote

Yeah, its defective.


PostPosted: Sat Dec 30, 2017 9:27 pm    Post subject: Reply with quote

It's a superb optic in a rather rattly plastic beer can. The older MF version is vastly superior in construction, but gives up the AF ability and the 1:1 magnification. The AF model is actually pretty rare as they were only made for a couple of years in the mid 80's before being replaced by the 60mm version. I'd say that yours has probably taken a knock or has been poorly reassembled at some stage as it should not be anything like that.


I can attest to the sharpness on a good sample, it's extreme at any distance.





PostPosted: Sun Dec 31, 2017 6:30 am    Post subject: Reply with quote

hellboy80 wrote:


f/5.6


f/3.5


Yeah, there is something very wrong with the optics, the center of the DOF should be razor sharp in both pictures, and at the very least, it should improve as it's stopped down, and it's not... at all.
You could send it to a lens tech to check that the elements are seated properly.


PostPosted: Tue Jan 02, 2018 3:53 am    Post subject: Reply with quote

The manual focus and AF on your reflex camera are separate mechanisms. The AF uses small secondary mirror under the main one. But manual focussing doesn't. Your pictures of the typeface look like back/front focus misalignment of the mirror or screen. Your camera might be set up OK for AF but need adjustment for manual. Usually a hex key slight turn.