[Flugelbinder]

I need some help please.
I have noticed before, but as the photos were from my baby girl, and we all know how (not) still babies get, I always assumed that would be the problem. Today I took some photos near a brick wall, and when pp'ing, the wall, in the middle of the image is soft. But with no sharpness at all!!! The stones on the ground are sharp and the bottom and top of the wall is also sharp, but the centre - where the subject was - isn't...
Anyone???

[SpecialK]

Post a sample image.

[Flugelbinder]

Of course...

[Steve.Ledger]

but the centre - where the subject was - isn't...

Wrong image?
This one has no subject in the centre, the shallow dof of course means it isn't sharp there..

[Flugelbinder]

Look at the wall.
It's sharp at the bottom, the centre isn't, and it's sharp again at the top...

[Na Horuk]

That's a good photo, but yes, the person's face is not sharp. Looks like its not motion blur. So it might be OoF or a lens issue.
The thing to remember with OoF is that the focus field is not actually flat. It bends on most lenses (exception being macro primes).
What I would suggest is you take a photo that tests sharpness and nothing else. Put camera on tripod, Av, ISO 100, 2 sec timer (or remote), switch to MF and twist the lens' focus ring to near minimum focus. Now get a piece of newspaper and place it in front of the lens at around the distance you are focusing on. The newspaper should be at 45 degrees to the camera, but parallel. Now take a photo (you might need EV+) and you will see where exactly the DoF is, as text will be sharp right across the middle of the newspaper, from the left edge to the right. You will notice how it bends. The question is, are there parts that are never sharp. Take a photo at lowest F number, then one higher, and then at f8. This should give you a good idea.
Another test you can do is that you try regular AF (AF-S, centre point), then live view AF (this is CD AF, works differently from the other), then live view MF with focus peaking. If one of these gives you sharp photos, then you know the problem is not the lens.

The problem with AF is that the focus point is much bigger than the overlay in the viewfinder, about as big as the ( ) in the middle. So often it will lock focus, but not where you wanted it to. The other problem is that DoF can be very shallow, so if the focus is only 2cm before the person, they will be OoF (only thin air will be in focus, and maybe some surrounding things). If the previous test shows the lens is sharp, then the problem is AF. It could be just being unfamiliar with it (with how Auto AF point works, AF-C, AF-S and so on), or it could be front/back focusing. IF this is it, there are numerous threads about it, that tell you how to use focus charts to calibrate the lens AF. There is a camera Menu option to help with this, called Focus adjust.

Take it slow, focusing is one of the most important and difficult parts of photography. People often take it for granted, because there is a machine AF, but it still takes skill

[manntax]

The thing to remember with OoF is that the focus field is not actually flat. It bends on most lenses (exception being macro primes).

This! Field curvature is often the culprit of all 'not-so-sharp-corners' or sometime subject in centre isn't sharper but corners are. In fact with most lenses you can try and focus in Live view on corner sharpness of something and you will see with lens wide open that centre is not as sharp as corner is ! - I am speaking about high quality primes - zooms might not be sharp in the corner at all until stopped down.

Another thing could be back or front focusing issues.

[clackers]

Flugelbinder, are you saying your focal point was the gentleman's eye?

[UncleVanya]

One thought that may more directly address the photo, if the brick at the bottom and top are sharp and the center isn't, don't forget these locations are at different distances from the focal plane. If you took a sting and measured the upper and lower parts of the wall would be farther than the center by a good margin when shot at an angle like this.

For a quick check take the classic brick wall shot, tripod, flat wall, face on not at any angle.

Also try a focus calibration chart to ensure you don't have a small problem with front or back focus.

[Flugelbinder]

This! Field curvature is often the culprit of all 'not-so-sharp-corners' or sometime subject in centre isn't sharper but corners are. In fact with most lenses you can try and focus in Live view on corner sharpness of something and you will see with lens wide open that centre is not as sharp as corner is ! - I am speaking about high quality primes - zooms might not be sharp in the corner at all until stopped down.

Another thing could be back or front focusing issues.

Humm, interesting... I also realized that it does have a bit of front focusing, but I'll take care of it and see how it goes...

---------- Post added 03-08-15 at 06:40 AM ----------

Flugelbinder, are you saying your focal point was the gentleman's eye?

Well, the face, but yes. Any reason why you might ask?

---------- Post added 03-08-15 at 06:43 AM ----------

One thought that may more directly address the photo, if the brick at the bottom and top are sharp and the center isn't, don't forget these locations are at different distances from the focal plane. If you took a sting and measured the upper and lower parts of the wall would be farther than the center by a good margin when shot at an angle like this.

For a quick check take the classic brick wall shot, tripod, flat wall, face on not at any angle.

Also try a focus calibration chart to ensure you don't have a small problem with front or back focus.

Going to try that.
So far, I have closed down the aperture to about 5, or 5.6, and that may have masked the issue a bit; it did with the front focus that I've only noticed yesterday...

---------- Post added 03-08-15 at 06:47 AM ----------

That's a good photo, but yes, the person's face is not sharp. Looks like its not motion blur. So it might be OoF or a lens issue.
The thing to remember with OoF is that the focus field is not actually flat. It bends on most lenses (exception being macro primes).
What I would suggest is you take a photo that tests sharpness and nothing else. Put camera on tripod, Av, ISO 100, 2 sec timer (or remote), switch to MF and twist the lens' focus ring to near minimum focus. Now get a piece of newspaper and place it in front of the lens at around the distance you are focusing on. The newspaper should be at 45 degrees to the camera, but parallel. Now take a photo (you might need EV+) and you will see where exactly the DoF is, as text will be sharp right across the middle of the newspaper, from the left edge to the right. You will notice how it bends. The question is, are there parts that are never sharp. Take a photo at lowest F number, then one higher, and then at f8. This should give you a good idea.
Another test you can do is that you try regular AF (AF-S, centre point), then live view AF (this is CD AF, works differently from the other), then live view MF with focus peaking. If one of these gives you sharp photos, then you know the problem is not the lens.

The problem with AF is that the focus point is much bigger than the overlay in the viewfinder, about as big as the ( ) in the middle. So often it will lock focus, but not where you wanted it to. The other problem is that DoF can be very shallow, so if the focus is only 2cm before the person, they will be OoF (only thin air will be in focus, and maybe some surrounding things). If the previous test shows the lens is sharp, then the problem is AF. It could be just being unfamiliar with it (with how Auto AF point works, AF-C, AF-S and so on), or it could be front/back focusing. IF this is it, there are numerous threads about it, that tell you how to use focus charts to calibrate the lens AF. There is a camera Menu option to help with this, called Focus adjust.

Take it slow, focusing is one of the most important and difficult parts of photography. People often take it for granted, because there is a machine AF, but it still takes skill

Thanks.
From my previous tests, I had settled with a +1 adjustment. It looks like it's a good compromise for shorter distances and I will have to test it in something further away, since it's slightly front focusing.

[Flugelbinder]

Ok, an update:
I got the front focus corrected, but the images weren't sharp yet. I then shot a few frames with the flash and they were very sharp. That got me thinking, and I turned the SR off, and, surprise surprise, the images from the same neighbour's wall were now sharp...
Can this be some problem with the SR?!?

[Na Horuk]

I think the SR would shake the whole frame, not just the centre. Make sure the lens is communicating the correct focal length to the camera (For manual lenses, input the exact number as written on the front, or the nearest wider focal length. For manual zoom lenses it gets more complicated, ideally you adjust for each zoom, or input middle number, or most used, or widest to be safe). Make sure the lens and camera contacts are clean
That being said, SR definitely can introduce shake, especially if you don't give it enough time to activate properly (there is an icon that shows up when SR becomes active after you half press the shutter), if the wrong focal length is input, or if camera is perfectly still (if tripod is used, you should disable SR, as there is nothing to correct, only perhaps fudge up)

[Oldbayrunner]

Are you doing all of this checking on your 55-300mm lens hand held or using a tripod?

[Flugelbinder]

Hand held. That's how I will use it in the field...

[Oldbayrunner]

Then you really need to insure your settings are correct or use a tripod when using that super zoom lens. Motion gets amplified and depth of field can be a lot narrower then using a mid telephoto or wide angle lens at the same aperture. Your showing in your Flickr stream some really good results with it when they appear to be correct and some one can expect for hand held when they aren't. In any case, the ones that aren't with proper post processing could be improved to an acceptable sharpness.