I was wondering if somebody else has the following problem or maybe knows how to deal with it.
Lately my Nikon D700 starts to overexposure alot in some shots. It looks like the sensitivity of the sensor goes up sometimes. I have included a sample serie of one bracketing serie of 9 shots. The mode was set to manual and the bracketing order is normal-under-over. The camera was placed on a tripod and all the shots were taken directly after each other. (the metering was set to matrix).
The problem occurs using all kinds of different functions (so not only bracketing or something) but until now i did not discover a real order of when it happens. One final remark. It looks like the problem only occurs while using the 24-70 2.8 lens..I did not have the problem using my 70-200 2.8. Thanks for all your help!,
Fri 16-Jan-09 02:51 AM | edited Fri 16-Jan-09 03:34 AM by TomCurious
For some of your shots, the lens aperture does not close to the commanded position. I.e. for the 3rd shot (-3 exposure, 1/60sec. f8 iso800), yes the metadata shows f/8, but the image was actually taken at around f/2.8. Just look at the background and compare it to your first picture which really was f/8.
Since the 24-70 is a "G" type of lens, all communication between camera and lens is electronic. First I'd recommend to inspect and clean the contacts of the lens. If this does not help and you only have this issue with this lens, and other lenses are ok on your camera, then your lens may be faulty and need service.
You can also press the DOF button a number of times and verify that it reliably closes the aperture down to f/8. This action uses the same communication contacts to the lens. If the DOF button always works fine (you always see the aperture change in the viewfinder), yet when taking pictures some are still overexposed, there may be a mechanical problem with the aperture blades sticking and not closing quite fast enough (they need to close in milliseconds when pressing the shutter).
Take Tom's advice and retest your camera carefully. You probably have a hardware problem.
Nevertheless, the D700 in Matrix mode is programmed to expose strongly to the right compared to the D300 and D200. This is a feature, not a bug. To compensate, I have dialled in a permanent -0.5EV exposure compensation for Matrix metering.
Also, Matrix metering on the D700 strongly favors the area immediately around the focus point.
D700 users (and all camera users) need to do two things. First, test the metering system carefully to learn how it works. In two hours you can take hundreds of sample images with all sorts of settings.
And second, once you learn how things work, watch the LCD histogram carefully to see what you are actually doing.
Cameras are just machines. You can figure out how yours works by making a few controlled exposures. It's fun, and you will end up with much better results.
>Nevertheless, the D700 in Matrix mode is programmed to expose >strongly to the right compared to the D300 and D200. This is >a feature, not a bug.
The examples posted by Dominic are all manual exposure. (I've only seen this when I checked the EXIF.) The D700 meter is indeed aggressive, which is important to know, but it's not related to this particular issue.
>D700 users (and all camera users) need to do two things. >First, test the metering system carefully to learn how it >works. In two hours you can take hundreds of sample images >with all sorts of settings.
This is good advice, but not at all relevant to Dominic's problem.
I would agree with Tom that the lens - or the stop-down mechanism in the camera - may require cleaning or adjustment.
Tom, thank you for this advice! Until now I was not thinking in this way so I will definitely clean/test it when I come home from work. Probably its indeed the lens because I even tried some more shots yesterday evening with 70-200 2.8, 50 1.8 and 10.5 2.8 and it still did not happen there.
@brian: what do you mean with the stop-down mechanism (sorry I am Dutch I maybe I dont know all the technical terms in English)
>@brian: what do you mean with the stop-down mechanism (sorry I >am Dutch I maybe I dont know all the technical terms in >English)
As I expect you know, Dominic, Nikon lenses stay at their maximum aperture while you are metering and focusing. They only close the aperture when you fully press the shutter release. Even if you have set f/8 as your aperture, your lens will be at f/2.8 until the moment you take the picture.
This "stopping down" is done by a mechanical linkage between the camera and the lens, in the lens mount. It's at about 3 o'clock if you're looking at a lens from the back. This linkage can stick if it is dirty or damaged, which can sometimes prevent the lens closing to the set aperture.
One other tip: when Nikon lenses are removed from the camera, the diaphragm blades should close to the smallest opening. If this doesn't happen when you look through a lens that's been removed from the camera, it's an easy indicator of a problem. Other good one is flicking the lever that Brian mentions. A correctly working Nikon-mount lens should open and close quickly when the lever is flicked with a finger.
thanks all for the help, I tried out the things you recommended and I discovered it's indeed the stopdown mechanism on the lens. That's why the problem only occurs with this lens. When I screwed off the lens the lens was closed, after opening and releasing the lever the lens had a lot of friction while closing or sometimes it even stayed open.
I tried to fix it a bit myself but the friction was not at the exit of the lever. So probably I will go to the service center soon to have it checked..or some of you must have a good idea..I am not sure if I want to open the lens myself.
thanks a lot, now I at least know what the reason is so its easier to have it fixed,
I wouldn't mess with it myself, unless you find that a succession of "flicks" of the diaphragm cures the stickiness. It's probably best to take it in and get it resolved in a way that will give you confidence.
It's not directly relevant to this issue of sticking blades, but I was wondering how exactly the camera sets the aperture. Can somebody clarify? I had assumed it was all electronic, the camera sending some signal via the lens contacts. But the fact that "G" lenses still have that lever mentioned by Brian and Rick makes me wonder, maybe that lever is used to set the aperture when taking the shot? Or if not, then what is the lever for?
I know that G lenses require the aperture to be set from the camera, but our discussion in this thread revealed that I don't exactly know how.
It's still the lever, but it's in concert with all the other stuff. It's easiest to understand with an AF or AF-D lens. If you set the aperture ring to f5.6, for example, you can see that the lens limits how far open the diaphragm blades will go when you move the lever away from its rest position. In the case of a G lens, the same thing happens, but the f/5.6 position is set electronically from the camera body to the lens. In the absence of a camera body, the limit is the widest aperture.
Hi to all o you, things have been clarified,regarding this issue.What i can add is that the lens stays wide open to help focus.Only when u fully press the shutter that the diaphragm closes to the set aperture.Then,we understand that faster lenses have an advantage on focusing speed. This being said,there are things that are not clear for me,abot these "flicks" etc. Read u on another forum. Tchao Ned