Blurry Photos

[whardman]

I am using a set ISO @ 200 (the lowest setting for the Nikon D50)


This is my best attempt with the focus card. 1/15 @ F 6.7, ISO 200, 280mm taken from about 9ft away. I cropped the photo so that the center of the original is still in the center of the cropped photo. It appears that the focus is in the center but that the entire photo is fuzzy.

 

[benhasajeep]

Take the same pic at f/11. And post it.

 

[whardman]

F11 @ 1/10 sec. Taken with the remote. Still has the same fuzziness.

 

[benhasajeep]

Ok, do one more pic checking for front focus and back focus. So the numbers go away from you and at an angle. With the lens at 6.7. Focus as best you can on the 0. Post the pic.

Also do you have any kind of filter on the lens?

 

[whardman]

I'm not quite sure what your asking "checking for front focus and back focus". Are you talking about placing the card at an angle so that the near and far number are out of focus. If so thats what I did in both photos the card is set at a 45° angle from the camera.

And no I do not have any filters on the lens.

 

[benhasajeep]

I'm not quite sure what your asking "checking for front focus and back focus". Are you talking about placing the card at an angle so that the near and far number are out of focus. If so thats what I did in both photos the card is set at a 45° angle from the camera.

And no I do not have any filters on the lens.

Ok, you did the angle from left to right. Didn't notice that at first. Harder to check with a long lens I guess. Front focusing is when you focus on an object and the lens focus is better on a closer object. Back focus is the opposite where it will focus on a farther object than your actually aiming at. I thought with that first roof shot, since you said you focused on the vent. That the lens / camera was front focusing.

And if you put on the kit lens the focus is spot on? I would say the sigma just has poorer qualities at the long end wide open. Which could be expected on any lens. The reason I asked for f11. As lenses perform better between the extremes of f/ stops.

Do you have a long ruler or something that is longer that you could do another front / back focus shot? Would like to know if the lens will have sharp focus at all. Will need to be back over 8 feet or so. If your lens has a focus chart you can find out how far you need to be back and where the front and back focus should be.

EDIT!
I just looked up a similar length sigma. 100-300 f/4.0. According to its depth of field chart. At 300mm at f/5.6 and 2 meter from the chart the dof is only .012 meters. That I believe is about 1/2". That is too hard to tell on the chart. Length of lens and distance makes a big difference on the dof chart and testing

Just used a dof calculation and your lens should have a dof of 1/2" at 72" from target 300mm and f6.7. So 1/2" on either side of the 0 or center line should be in sharp focus.

I am not sure if it makes a difference but I have always seen the chart at a 45 deg angle from top to bottom not left to right or both. Must be easier that way since its the short dimension in the framing.

 

[whardman]

This left photo was taken @ F11 2.5 sec @ 250mm. The ruler was at a 70° angle, 6.5 ft from the camera. It is centered slightly to the right of 18 inches. The right photo was taken at F6.3 1 sec. The rest of the setup was the same. The center is the top of the 1 on the 18.



The left image is back focused the right image is center focued but not as sharp, although much sharper than the earlier photos.

The kit lens is spot on in the focus.

EDIT: There is about 8 inches of depth between the 14 and 22.

 

[benhasajeep]

Look like the lens is probably working correctly. Just at the extreme telephoto length and extreme f/ stop. It shows its weaknesses. Whats funny is on the first roof shot it front focused, and on the first ruler shot it backed focused. Maybe there is a loose element problem. Does the seem solid? No movements when zooming or focusing?

I read up a little on the lens and I guess its very compact for its range. I found a review on popphoto. Your airplane shot is definatly out of the norm. http://www.popphoto.com/assets/download/3302003194022.pdf

Do you have exif information on the airplane shot. I just noticed that in similar outdoor conditions between the house and plane. The airplane is 2.5 stops faster shutter speed. Make me wonder if the iso on that shot was closer to 800 than 200? It's out of focus, but I think the noise makes it look worse. I think maybe the plane pic is just not a good example. Maybe some movement, high iso, and lens at extreme all accounted for the bad pic. The roof pics are not that bad. Although the fisrt pic not focused on what you wanted.

A good mystery.

 

[whardman]

The airplane shot is most likely ISO 200. I was shooting most of these on program auto so that I could set the ISO at 200.

I don't notice anything loose or any extraneous movement when zooming or focusing but would not be 100% without taking it apart. The airplane shot is probably not the best example as it does incorperate some extreme conditions. But then I see crisp pictures like this at 400mm. http://www.jetphotos.net/viewphoto.php?id=548077&showexif=1#exifshow

Oh well, probably a factor of a few things causing the blurriness.

Thanks for all your help.

 

[benhasajeep]

The airplane shot is most likely ISO 200. I was shooting most of these on program auto so that I could set the ISO at 200.

I don't notice anything loose or any extraneous movement when zooming or focusing but would not be 100% without taking it apart. The airplane shot is probably not the best example as it does incorperate some extreme conditions. But then I see crisp pictures like this at 400mm. http://www.jetphotos.net/viewphoto.php?id=548077&showexif=1#exifshow

Oh well, probably a factor of a few things causing the blurriness.

Thanks for all your help.

Well being digital, it doesn't cost anything other than time to do some more test shots. Maybe if there is a local airport. Go out and experiment with speeds, iso, aperature. See what the lens / camera combo can do. Most small planes like the Malibu should be within the same area of view on takeoff, definately on landing (50' above the ground at end of runway). If the airport if busy enough should get quite a few shots.

That just made me think of something else. What focus mode did you use for the shot? The plane was accelerating, climbing and turning away from you. So if the focus locked say while the plane was say 50' closer to you. And you hit the shutter the rest of the way just a little later. It will be out of focus! Should be in AF-C. Supposed to have predective tracking of moving objects.

I have not had my D50 that long so I had to look it up. The camera is supposed to pick between servo AF-A and AF-C with just the af switch set to AF. But if you go into custom function 2 you can set it. I bet the camera was in servo when the pic was taken and since the plane was moving it missed focus.

 

[whardman]

I had it in AF-A (auto) mode. I find that it does a decent job of retaining the focus of the object that I pointed it at if it is moving. If I move the camera off of a subject it has a tendency to retain the focus that it initially had. As the plane was not centered perfectly in the original photo it could have focused off slightly.