Why is this happening.........?

[John_M_King]

I have been outside today to test my new D700 and the results I got were somewhat surprising.

The 1st image was taken using a 28-70AFD lens at 28mm. As you see it is perfectly normal.

The 2nd image was taken with a Sigma 15-30EX at 15mm. There is as you see a portion of the image cut off but you can see ghosting underneath.

The 3rd image was taken with the same lens indoors after I found the 'error' but using flash, again there is ghosting under the circular cut off section.

When I took them, the images 2&3 shown on the screen were perfectly normal it was only when I transferred the images to the computer that the problem became apparent. The original images were taken on RAW (14bit) and processed through Nikon NX and Adobe RAW then Photoshop CS4. Initially the images were perfect then suddenly changed to give the circular cut off as you see here.

When using the lens with my Film cameras there has never been a problem whatsoever with edge to edge coverage.

As the 15-30 lens is quite old (but still good) I wonder if it cannot handle the modern electronics and especially RAW capture?
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Update.

I have just shot another 4 images using flash,- 2 x RAW and 2 x jpg and they are perfect. I changed the Raw setting to 12bit from 14bit and this seems to be the answer. so it may be due to the age of the lens and nothing else unless others have any suggestions..

 

[L Gebhardt]

Is the issue the same with NX and the Adobe converters?

 

[John_M_King]

Both systems

As I mentioned before the only way around it is to use the 12 bit and not the 14 bit Raw capture. It does not happen with genuine Nikon lenses as shown with the 28/70AFD lens. Obviously as the 15/30 lens was current before the D700 was made. It wasn't/isn't obvious on the D90 I have either, which only has a 12 bit RAW mode, plus the centre oprtion is the only part used.

The fault does not show on the camera screen nor does it occurr with my Sigma 105mm Macro lens, but there again that optic is a current model.

 

[Eric Rose]

Looks like you are using DX lenses on an FX body. You can set the D700 to DX mode.

 

[480sparky]

Looks like you are using DX lenses on an FX body. You can set the D700 to DX mode.

Explain how the camera can create the 'rest' of the image outside the circle.

When using a DX lens on an FX body, set to FX mode, the outer portions of the image are black... not the remaining part of the image.

 

[L Gebhardt]

That really makes no sense if other lenses don't do the same thing with 14bit mode. I can't imagine what the camera is doing to the raw file based on the lens and the bit depth that would do this.

 

[John_M_King]

Eric. I can say with absolute certainty that the 15/30 Sigma is not a DX type lens. I use it on my F6 and F100 with no problem at all. Also using it with the D700 set on 12 bit Raw and Jpg the results are perfectly satisfactory.

I am going to get in touch with Sigma UK to see if they can provide the answer.

 

[OzJohn]

Looks like you are using DX lenses on an FX body. You can set the D700 to DX mode.

DX lenses on a FX camera do not produce such a symmetrical "vignette". BTW - switching the D700 to DX mode is not the the best way to use such lenses because it reduces the available pixels to around 5meg. The best way is to switch off auto DX sensing and just let the vignetting occur - it is only a problem with wide angles and to a minor degree with some standards and even after cropping in post you will most often end up with a much bigger file. You won't read this in the manual but it works and works well. OzJohn

 

[John_M_King]

I have just come off the 'phone to the Tech Department at Sigma Imaging UK and after explaining the problem they have stated that the lens I had the problem with is probably over 10 years old and the technology in the electronics involved with Nikon NX software and the D700 are in advance of the technology in volved with RAW data in the D700 when using 14bit RAW however the 12 bit RAW will work perfectly.

 

[L Gebhardt]

I have just come off the 'phone to the Tech Department at Sigma Imaging UK and after explaining the problem they have stated that the lens I had the problem with is probably over 10 years old and the technology in the electronics involved with Nikon NX software and the D700 are in advance of the technology in volved with RAW data in the D700 when using 14bit RAW however the 12 bit RAW will work perfectly.

That seems really odd. It seems the camera is doing something to correct vignetting or distortion based on the lens data. However this shouldn't be happening while writing a raw file, at least in how I understand raw files. I think the D700 have a vignette correction setting. Have you tried turning that off? My guess is a bug in the camera with 14bit and some lens information, as wrong as that sounds to me.

 

[John_M_King]

I have tried to make it clear that this only happens with the 15/30 lens and no other. Non of my Nikon Lenses give any problem, so I am prepared to accept the Sigma explanation. No phenomena such as can be seen in the images which were attached, took place with either my 28/70AFD, 70/300AFD, 28/200AFD or the Sigma 105mm Macro lens which is a current model.

It is not vignetting in the accepted meaning of the word because outside the ring the image is clear and complete, and is still visible, although very faded under the area covered by the rings.

There is no problem either recording in Jpg or Tiff.

The 15/30 EX lens, is as I said, probably 10 years old and possibly older, which means it was made at least 3 years before the D700 was sold in UK. 14 bit capture it seems is just not compatible with this lens. Obviously Nikon would not be prepared to comment, they never do with 3rd party lenses.

There is 1 plus point. The image of the fence is taken almost directly into the midday sun this January and there is no trace of flare. If I had been using film in any of my film cameras it would have shown quite a bit of flare (It can be quite bad) probably from the top right hand corner. The same cn be said with the image of the rabbit tracks in the snow, the sun was just out of view at the top of the frame in the middle.

 

[L Gebhardt]

John, if the camera didn't get any data from the lens it would have to be fully compatible in 14 bit or 12 bit mode, since the lens is just projecting an image on the sensor. So the issue has to be how the D700 is using the data it gets from the lens. It's all academic at this point if Sigma won't update the lens and Nikon won't update the D700.

Would you be willing to send me one of the RAW files with this issue? I want to take a look at it just out of curiosity.

 

[John_M_King]

There has been a bit of a development with this saga, although I don't fully understand why. The initial problem pictures were taken using two genuine Nikon lenses - 28/70 AFD and a 70/300 AFD and of course the Sigma 15/30EX. I used both both Nikon NX software to convert the raw files, as well as Adobe RAW converter. So far so good. The lenses made by Nikon showed no evidence of the phenomena, whereas the Sigma one did.

I have taken a further series using only the 15/30 set to capture at 14 bit RAW. When I down-loaded them through the computer I used ONLY Adobe Raw to process them - and - hey presto - no signs of the dreaded rings.

In conclusion there seems to be some degree of incompatability between the lens, its electronics and Nikon NX software, but only when used with 14 bit RAW, because when using 12 bit the problem does not appear at all whatever software I use. It sounds like an age related thing with the Sigma lens not having more up to date electronics.

 

[Doyle Thomas]

sounds like u have found a work around. u gotta do what u gotta do lol