Hi, I wonderi if anyone has any idea what could be causin the top centre focus point of my d5100 to be causeing problems?
what happens is this..
My problem is that the camera often cannot lock focus with this focus point, whereas it can when pointing at the same subject in the same conditions with the same settings. The camera can also appear to freeze when using the top sensor. It can also freeze when using area focus or automatic mode, but I never use those settings.
I have tried this camera with so many settings with the same results I am getting myself lost. Here are the settings of my latest try,.
Mode dial "S" qual "norm" "L" wb "auto" iso "auto" max sensitivity 3200 min shutter speed 1/160 single release mode AF-S single point AF metering centered ADL OFF bkt OFF Portrait mode EC = 0 flash OFF AF assist lamp OFF
The behaviour of the focus sensors selected is what I expected
D5100 behaviour of focus points with the 18-105
1. All focus points except the top one.
If the camera is pointed at an area of no contrast and the shutter button is released, the lens tries to focus. The lens does not achieve focus, the lens stops hunting and the green "focus achieved" lamp flashes. The lens seems to make two separate noises as it hunts, presumably as the lens goes from minimum to maximum, then back. If the shutter release is pressed again, the camera tries to achieve focus again by repeating the cycle. If the camera is then pointed at an area of higher contrast, focus is achieved, the lens stops focussing and the green "focus achieved" light in the bottom-left of the viewfinder is lit. The photograph is in focus.
If the camera is pointed at an area of higher contrast, focus is achieved, the lens stops focussing and the green "focus achieved" light in the bottom-left of the viewfinder is lit. The photograph is in focus.
The centre focus point is more sensitive and achieved focus more easily than the others.
The top centre focus point did not behave as I expected.
2. The top centre focus point.
If the camera is pointed at the same area of no contrast and the shutter button is released, the lens tries to focus. The lens does not achieve focus, the lens stops hunting and the green "focus achieved" lamp DOES NOT light up at all, it does not even flash once and the camera seems to freeze. The lens seems to make one single noise rather than the two separate noises as it hunts, presumably as the lens goes from minimum to maximum only. If the shutter button is pressed again, nothing happens, the camera will not try and focus, even if the shutter release is pressed repeatedly.
If the camera is then pointed at an area of higher contrast, two things can happen - the lens does not achieve focus, the lens stops hunting and the green "focus achieved" lamp flashes or- if the contrast is high enough, the camera "finds" focus and takes a picture. This picture can be front focussed though, the focus is not reliable. This may be due to a repeating pattern in the photo though.
If the camera is pointed at an area of very high contrast like the vertical edge of a monitor, focus is achieved, the lens stops focussing and the green "focus achieved" light in the bottom-left of the viewfinder is lit. The photograph is in focus.
If I put the camera in auto area mode. -
The camera sometimes will not achieve focus or the "focus achieved" lamp light up and the camera can freeze. Presumably this is when it uses the top middle focus sensor on a low contrast area.
To give you an idea of the conditions I was taking photos in, the photographs that could be taken had the parameters in the range
iso in the range 560 - 900 shutter speed 1/160 apperture f3.5
As the top centre sensor is behaving differently from the others of the same type, I believe there is a fault with this camera. As the top centre sensor is critical for the photos I want to take, this is creating problems for me.
This camera has been to Nikon (UK) twice and returned to me as in working order. I guess of they only test the focus with well-lit high contrast focusing charts, then they wouldn't see the problem. But I have explained everything to them several times.
#1. "RE: Focus problems with my D5100" In response to Reply # 0
Welcome to Nikonians! Most of what you discribe sounds perfectly normal. Keep in mind that the Multi-Cam 1000 AF module in the D5100 has only one cross type sensor (center) that is the most sensitive. The surrounding sensors including the upper center sensor are less sensitive.
For AF to work coorectly the AF target must have contrast. The higher the contrast, the better the AF target. See page 40 in the D5100 Users Manual . Good Luck and Enjoy your Nikons!
#2. "RE: Focus problems with my D5100" In response to Reply # 1
Hi, thanks for the reply.
I agree that all of what I describe for all the sensors, with the exception of the top one, is normal.
Section 6 of p27 of the manual only gives 2 options for the "in-focus indicator" with the shutter release half-depressed, blinking for out of focus or steady for in focus.
It is not normal that the in-focus indicator does NOT either blink to show out-of focus or show a steady green light. It is not normal for a camera to freeze like this one does. That is what happens with the top sensor. It does not happen with any other sensor. It can freeze when using area mode too, and it is very annoying. The top focus sensor is clearly much less sensitive than any of the others, making the top sensor and area mode unusable.
I am trying hard to enjoy this camera, but it doesn't work properly with the top sensor, which is the most important one for me.
#3. "RE: Focus problems with my D5100" In response to Reply # 0 Thu 19-Jan-12 02:39 PM by Leonard62
Hatboro, Pa, US
My D5100 and also my D200 act the way you describe. And that's with the AFS 50mm f1.8G lens. Except in my case the upper and lower points don't acquire. My room is well lit and this is my target. I was about 10 feet away.
I had no trouble with my D300, D700, D1H, D2X or D3X.
If your application requires focus on a lower contrast target at the outer points it sounds like you need a body with a better AF system.
Edit: To better understand the AF performance of each Nikon body you should know the pattern and number of the most sensitive sensors, the cross type sensor. Here is the number of cross type sensors for some popular Nikon models
#4. "RE: Focus problems with my D5100" In response to Reply # 3
Thanks for the replies so far. Looking further, I think I may have made some progress as to what the problem may be. I tried to get the camera to deliberately freeze in auto-area focus mode using the 18-105 lens.
It did, and it froze with the focus about 9 inches from the front of the lens.
I repeated it with only the top sensor selected and it froze again at about 9 inches from the front of the lens.
So I think this is what's happening - the focus seems to freeze at the minimum focus point of the lens when it uses the top sensor in poor light or low contrast. The camera cannot complete the focus routine to give "focus attained" or "no focus attained" so it cannot try to refocus if the shutter release is half-pressed again no matter how many times, presumably because the image the focus sensor sees is all blurred. The only way to get the camera to try and refocus is by
1 pointing it towards a light to give it something very high contrast
2 holding my hand about 9 inches away from the front of the lens so the camera can find something to focus on.
3 changing the focus point selected
All the other sensors functioned normally, i.e. they could focus in the same conditions. When they could not attain focus, the camera would try to refocus if the shutter release was half-pressed, which is perfect.