Somasipper
Active member
Before purchasing a D70 I researched the possibility of this issue thoroughly. I found the solution before I even had a problem. Hope it helps you too. This is my summation of what I found.
There are some important mechanics of focus you should remember before doing a backfocus test.
First off, and the most important thing to understand before claiming back focus, Anything closer to the camera then the focus distance will be blurred twice as much as something behind the point of focus. Let’s say you focus on a tree 20 feet away. A second tree that is 40 feet back will look just as focused as a third tree 10 feet away. In other words things behind the focus point are twice as clear as things in front of it. This is why we see a lot of people complaining about back focus but no front focus. It is more often then not a misinterpretation especially on the famous ruler test.
Secondly, The auto sensor (only the central one) covers a large amount of the frame. The camera will not necessarily focus on the middle of the sensor, if there is something further back but still within the auto focus zone, it may pick, and often does because its easier to find contrast in small thinner features. This is true even in closest subject mode, which chooses from which of the 5 auto focus zones are closest, but not what is closest in any one zone.
Finally, all lenses do not have infinitely perfect focus motors. They move in spurts, and will only reach an approximation, never the exact point. Combine this with the other two points and you will see back focus in any camera at random times. Higher quality lenses, and many macro lenses will have finer focus motors, but in the end the camera and lens can never really focus exactly where you want it to, nor will it know exactly where you want to focus at all. It’s a machine that tries to approximate a goal, and its your job to learn how to make the machine work properly.
This camera uses the same auto focus system as many other camera that have no problems other then occasional manufacturer defect.
With that said, one thing can be concluded. .When it is used with the same lenses used for years on other Nikons, there is not going to be a higher rate of focus issues then with any other camera with Cam900 auto focus(n55,n75,S2,D100,list goes on……).
Since the kit lens is not widely used on any camera other then this one I will not include it in this statement. It may have an unusually coarse auto focus motor, but I haven’t noticed it myself.
There are some important mechanics of focus you should remember before doing a backfocus test.
First off, and the most important thing to understand before claiming back focus, Anything closer to the camera then the focus distance will be blurred twice as much as something behind the point of focus. Let’s say you focus on a tree 20 feet away. A second tree that is 40 feet back will look just as focused as a third tree 10 feet away. In other words things behind the focus point are twice as clear as things in front of it. This is why we see a lot of people complaining about back focus but no front focus. It is more often then not a misinterpretation especially on the famous ruler test.
Secondly, The auto sensor (only the central one) covers a large amount of the frame. The camera will not necessarily focus on the middle of the sensor, if there is something further back but still within the auto focus zone, it may pick, and often does because its easier to find contrast in small thinner features. This is true even in closest subject mode, which chooses from which of the 5 auto focus zones are closest, but not what is closest in any one zone.
Finally, all lenses do not have infinitely perfect focus motors. They move in spurts, and will only reach an approximation, never the exact point. Combine this with the other two points and you will see back focus in any camera at random times. Higher quality lenses, and many macro lenses will have finer focus motors, but in the end the camera and lens can never really focus exactly where you want it to, nor will it know exactly where you want to focus at all. It’s a machine that tries to approximate a goal, and its your job to learn how to make the machine work properly.
This camera uses the same auto focus system as many other camera that have no problems other then occasional manufacturer defect.
With that said, one thing can be concluded. .When it is used with the same lenses used for years on other Nikons, there is not going to be a higher rate of focus issues then with any other camera with Cam900 auto focus(n55,n75,S2,D100,list goes on……).
Since the kit lens is not widely used on any camera other then this one I will not include it in this statement. It may have an unusually coarse auto focus motor, but I haven’t noticed it myself.
