D300 AF Assist Lamp leaking light to sensor

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D300 AF Assist Lamp leaking light to sensor

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D300 AF assist light leakage

RichJB

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Hi, I read on DPreview (D300 forum) someone having trouble with a bright artefact in his pictures when taking long exposures in daylight, such as when using a 10 stop ND filter. He suggested that D300 owners take a 30 second exposure with the lens cap on and at f16. I did the test and mine also has the artefact and is exactly the same shape. If there are any D300 users on here, he is trying to gather evidence that it is a common problem and not an isolated case. He has posted his email address for replies.
I haven't had any problems in the real world taking long exposures, but my darkest ND filters is only 3 stops.I feel that Nikon should address this matter if it is common. Any thoughts on this?

Rich.

Posted 2 years ago #
NSXType-R

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Not sure if I'm misunderstanding this or not, but what does your post have to do with the title of your thread, pertaining to the AF assist lamp?

Posted 2 years ago #
RichJB

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Sorry for not making my post clearer, what I was trying to say is that the AF assist light fitting allows stray light to leak into the camera. It occurs on very long exposures during daylight hours such as when you are using a strong ND filter. I was only aware of it today after reading a thread on DPreview and it seems it doesn't effect all D300's, but mine is affected. I have been in touch with the poster of the thread on DPR and also I have emailed Nikon Europe and attached my test picture. I don't use very strong ND filters, so I haven't come across it until now, but I guess anyone with a decent camera wants it to be as perfect as possible.

Rich.

Posted 2 years ago #
bmxdad

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Maybe Rick you should show a few sample pics:

OK, the AF light can not get activated with lens cap on, the light goes out after AF is found and picture is getting exposed

I just took a 20 min picture with NR off, and had no problems outside the hot pixels that NR would have removed

If you used a 10 stop ND filter your AF would be useless anyway, M/F no light right

Pete

Maybe it's a UFO

Posted 2 years ago #
wafwot

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I don't think the leak is caused by the illuminated light itself. I think Rich is saying the ambient light is leaking into the D300 through the clear lens of the AF light.

The original DPreview post is here:
http://forums.dpreview.com/forums/readflat.asp?forum=1039&message=35662356

Posted 2 years ago #
RichJB

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Thanks wafwot, for putting it better than I did. I will try some black tape on the AF assist light tomorrow, but I can't find any today. It is stray light from around the light, not the light itself. The pattern of light is identical to the OP on DPR. I want to say that I have never experienced it in the real world as I have never used such a strong ND filter, but I am left wondering how many other people with D300's have this problem and have no idea why they get the bright artefact in their pictures, when exposing with a really dense filter.

Rich.

Posted 2 years ago #
RichJB

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Here is the picture, sorry for the time I took to post one:

Posted 2 years ago #
NSXType-R

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Ah, I see what you mean now. But if light was leaking in through the AF light lens, shouldn't it be more to the right? Unless of course it's bouncing around inside the camera.

Posted 2 years ago #
RichJB

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I'm not sure how the light manages to find it's way to the top centre/left but it does. Some of the posters on DPR covered the AF assist lamp with black electrical tape and stopped it. I may try that today just for my own peace of mind, but I don't need to always have it covered as I have never used a 10 stop ND filter and haven't found it to be a problem. Do any of you think I should try and have Nikon Europe repair it? It is after all a design fault, but my camera is way out of guarantee now.

Rich.

Posted 2 years ago #
bmxdad

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Hi Rich

Sorry but I misunderstood you problem to begin with, anyway I tried this morning to see if I have a leak like yours

Anyway, I exposed for 5 min in sunlight with cap on, and only got a black screen, so there is certainly something wrong with your camera

So actually your camera is always having a small leak, just that brighter exposures will mask it. I think you should do a 5 min exposure, contact Nikon and explain what is going on and to be fair how would you have ever discovered this problem from normal use. I would newer have checked my Camera if you had not started this thread.

I hope for you that Nikon will help you out

Pete

Posted 2 years ago #
jonnyapple

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NSX, don't forget that the top center left of an image is actually the bottom center right of the sensor (as seen from behind the camera), so I think it does make sense that it's where this light shows up.

The fact that it's always in the same place no matter where the light source is makes me think it must come through the part that's cut out in the back of the mirror housing wall so the levers to move the mirror can get to the mirror. There's probably a direct line of sight from that part of the sensor through the cut to the AF-assist lamp housing.

Posted 2 years ago #
NSXType-R

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jonnyapple said:
NSX, don't forget that the top center left of an image is actually the bottom center right of the sensor (as seen from behind the camera), so I think it does make sense that it's where this light shows up.

The fact that it's always in the same place no matter where the light source is makes me think it must come through the part that's cut out in the back of the mirror housing wall so the levers to move the mirror can get to the mirror. There's probably a direct line of sight from that part of the sensor through the cut to the AF-assist lamp housing.

Ah, good point. I forgot about that.

Posted 2 years ago #
RichJB

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Hi Guys, thanks for your replies, I have heard back from Nikon and here is the first paragraph of their email:
Dear Richard,

Thank you for contacting Nikon Support regarding the D300 light leak.

I am sorry to learn of the problems that you have been experiencing with your Nikon equipment. It seems that your camera has developed a fault that has to be addressed at our Service Department. Please note that the turnaround time is generally between 2 and 4 weeks - depending on part availability, testing requirements, etc. Also, we are not able to guarantee the repair will be carried out on warranty conditions until the camera is physically inspected.

My camera is well outside the warranty so I wont follow it through. I did some test today, using the only two ND filters I have which are a ND2 and an ND4, I stacked them together and set my 70-300 lens to f32, the ISO to 100 and pointed it at the sky, nothing shows up, the exposure was moderately short, around 10 secs (from memory). I took some more with the cap on and black masking tape around the AF lamp, I used it sparingly at first, to see if the light was coming in from one portion of the AF lamp housing, a very thin strip which I repeatedly moved around for each exposure. I always ended up with the blue artefact. I found that even the slightest opening through the tape caused it, but if I masked the lamp completely it was fine. So I have concluded it is definitely a problem with how the lamp is seated. I am wondering if there is a seal around it that is possibly pinched or badly seated.
Anyway, thanks for replying, Rich.

Posted 2 years ago #
bmxdad

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I think the only way that you might see it is if the area being exposed is also a dark area where the the light leak shows up. The problem would be hard to see in real pictures, but that does not take away from the fact that the problem is there.

My advice: I am in Camera Sales and I know how cold the answer is from Nikon(or any other brand for that matter) service. So I would contact the place that the camera is bought from and somehow get to talk to a Nikon Sales rep, the reps that I deal with are more helpful if they can.

Explain to them that this is not a new developed problem, it is a manufacture fault that you have discovered from reading about another D300 having the same problem

Again hope you find someone at Nikon that will listen, could be worse if you had to deal with Nikon Service in Poland

Pete

Posted 2 years ago #
RichJB

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Thanks Pete, I will contact the store where I bought it, they are a very long established company and have a good reputation. I don't want to be without my camera for a long period as it is my only camera and it would be like having my right arm cut off. I have been in contact with the original poster on DPR and he says only one other person has contacted him with this problem. He feels the same way regarding the time Nikon want the camera but his is still in warranty so he may get it sorted, but Nikon has not committed themselves regarding it being a manufacturing problem to him either.
Rich.

Posted 2 years ago #

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D300 AF Assist Lamp leaking light to sensor

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