Magenta band

Bigfatmole

Senior Member
Hi guys ,
Has anyone else experienced this . ISO 5000+ taken a photo with a dark object at the bottom of the frame , ie black coat , tv ect . I'm noticing a magenta band at the bottom of the frame where the shadows/ darks objects are . If I turn camera upside down so the other side of the sensor has a go it is fine and now anything dark or black at the top has a magenta area .. I'm on my 2nd D810 now and this one does the same all be it not as bad as the 1st one. Should I be returning this one also or is this a trate with this camera
 

Bigfatmole

Senior Member
I will upload a shot when I can . It's showing up more in camera than it is on screen . I'm not sure if I'm being just too picky . Or will I ever see it in real life shooting .. I just wondered if anyone else had seen anything like this on their D810 .

can you get viewfinder bleed on a shot 1/50th second , what I'm experiencing is not a long exposure shot .
 

Bigfatmole

Senior Member
It's not so easy to see , but the bear should not have a magenta cast to bottom of his belly . Straight out of camera it's not so easy to see but when you start to process the photo it's starts to become more apparent. Hopefully it will be evident in the photo uploaded

im worried it will show up when I shoot my local hospital stage show , no flash allowed . This magenta strip is not easy to get rid of as it only shows up in the darks areas of the photo .. image.jpg
 

wornish

Senior Member
Can't see anything wrong on the example you posted.

There is no EXIF included but of this is a long exposure then it could be light leakage as said before.
 

Bigfatmole

Senior Member
It isn't the best example, but the area between his arms on his belly at the bottom should not be that colour , if you zoom in you can see the magenta cast where this area was darker than the arms ... Sorry wornish , for some reason my exif data never displays . It's 50mm prime f1.8 at 1/50th second ISO 5000. It does it on any of my lenses inc 24-70 2.8

being that hat this post is in D810 area has anyone else with D810 noticed a magenta band when using high ISO
 

480sparky

Senior Member
I'm seeing a red tinge to the bear's tummy, but that may be due to it being that color.

I'm not seeing a magenta strip or stripe or band.
 

Bigfatmole

Senior Member
If it was dark along the whole bottom you would see the band goes full length , but on this the shadows lighten each side at which point the magenta can't be seen , it only shows up in the darker areas .. The red tinge you see goes up half way between bottom n his collar .. This is the effected area .
 

skene

Senior Member
What you are probably seeing is light refraction from the material itself. I would suggest shooting the bear in a different lighting scenario to verify.
 

Bigfatmole

Senior Member
Hi mate my profile does have all my gear listed , until I just tried to change D610 to D810 now it won't even list a camera lol

ive tried many different scenarios and not the bear ... Anything black will highlight the issue .. However if I turn the camera upside down to put the other side of sensor on the dark area it works fine .. Can't help thinking its an issue with one side of the sensor or maybe viewfinder bleed .
 

Vixen

Senior Member
I see it clearly also. The only times I have had light leakage it has shown up as green & magenta bands across the middle of the shots. Maybe try to get some shots with black across the entire bottom, then with camera upside down and email Nikon.
 

wornish

Senior Member
One way to check if its light leaking through the viewfinder is to take shots with the lens cap on at say two different iso settings,

640 and 6400

all with camera set in manual at the same shutter speed and f/3.5 aperture and the viewfinder cover open
, then repeat with viewfinder cover closed.

Heres some I just tried. I purposely held the camera with the back towards the window.

The only one I got any noise on was iso6400, 10 secs with the viewfinder cover open. With it closed it was completely black. all the others were black.


iso6400 10 sec cover open, some noise as expected.
leak test-4.jpg


iso 6400 10 sec cover closed
leak test-5.jpg


iso 640 10 sec cover open
leak test-6.jpg


iso640 10sec cover closed
leak test-7.jpg
 
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enzodiac

New member
I am new to the forum and was looking for this exact problem. From looking around the web and trying things myself I would say this is amp glow. I had a D810 a couple of months ago and noticed this VERY clearly shooting indoors at iso 3200 and up. We have a black sofa at home and it basically came out all purple at the bottom of the frame.

I sold the d810 and got the d750 in hopes of this amp glow thing being better because of the lower megapixel count. I had read that the amp glow was basically gone on the d750.
Unfortunately it is not.

I have attached an example from the d750. But I had the exact same problem with the d810.

Ampglow.jpg

Now I know I am shooting at iso 11400. In fact I was very happy with the d810 noise levels even at iso 12800.
But this glow thing just ruins some shots! It doesn't show as much shooting jpeg but that's only because the blacks are kind of crushed in Nikon jpegs.

Should it be this way? Maybe it's just bad ACR support?

edit: the small picture in this thread doesn't do it justice. I have uploaded an example on my dropbox instead.
https://www.dropbox.com/s/eeh3bqj0len0tjr/ampglow.jpg?dl=0
 
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J-see

Senior Member
I am new to the forum and was looking for this exact problem. From looking around the web and trying things myself I would say this is amp glow. I had a D810 a couple of months ago and noticed this VERY clearly shooting indoors at iso 3200 and up. We have a black sofa at home and it basically came out all purple at the bottom of the frame.

Did you check your histogram? Usually if you shoot high ISO it is low light and seeing purple indicates you lost a part of a color channel due to clipping. I see this frequently in night shots, the darkest part of a shot during low light very fast loses a color channel and will usually appear purple. Take it a step further and it'll be clipped black.

Not to mention those parts have a that low photon count the noise will rule the pixel read-out because of amplification.

I don't see magenta bands in any of the shots. I see clipping in the darkest parts.
 
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enzodiac

New member
J-see. This shot was exposed very well I would say. The blacks are FAR from being crushed. I can underexpose that shot 4 stops without getting any clipping in the shadows. Maybe it's just the new cameras exposing very much "to the right" in the histogram. Dropping the exposure 1 stop and pulling down on the black will basically make this go away, but then I wont see any details in the shadows at all.

I updated my original post with a higher res version of the image on my dropbox. You can't see the purple? Compare the black sofa top left to the black sofa/floor bottom right.
 

J-see

Senior Member
Exposure has little to do with it. At least the exposure the cam indicates as correct. That's shot exposure.

The problem is that your sensor receives very little light. ISO is post-sensor, it only amplifies the read-out but has no effect on the incoming light.

I very often have black turn into purple and only and always during low light situations. Increasing ISO does nothing besides make it more visible. If it is clipping, you should never see it in shots when there is plenty of light.

When you pull down the blacks it disappears and that's normal since it is a value close to the clipping point which is pure black.

The higher the ISO you use, the more you'll see this kind of behavior. In the end, you're just upping the noise in those pixels.
 
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enzodiac

New member
Ok I am with you. And you are right, I never see it in wildlife shots outdoors. But I have never noticed this on my d3s for example. Sure that is only 12mp and it might happen higher up in the iso range. But then again it is 5+ years old sensor tech. I just thought sensor tech had improved over the years, I guess we just have more megapixels. And if the native iso goes to 12800 I think we shouldn't see this magenta cast at all. Noise is one thing and I don't mind a really noisy image at all. But this magenta cast makes it pretty useless for low light shooting. Unless we convert to b&w.
 

J-see

Senior Member
Ok I am with you. And you are right, I never see it in wildlife shots outdoors. But I have never noticed this on my d3s for example. Sure that is only 12mp and it might happen higher up in the iso range. But then again it is 5+ years old sensor tech. I just thought sensor tech had improved over the years, I guess we just have more megapixels. And if the native iso goes to 12800 I think we shouldn't see this magenta cast at all. Noise is one thing and I don't mind a really noisy image at all. But this magenta cast makes it pretty useless for low light shooting. Unless we convert to b&w.

The amount of pixels matters less than the technical aspects of your cam. It's possible you don't notice this in a 3Ds because it simply lost that information directly into clipping or because its pixel pitch is larger which resulted into less signal noise. I don't know about the 3Ds but the 4Ds has a phenomenal pixel pitch which results into a much higher SNR during identical situations. The D810 has a slightly smaller pixel pitch than the D750 which makes this problem appear on it a bit faster.

I shoot 100 ISO only and see those magentas appear too. The cam can't do anything about that nor can ISO. It's simply a lack of light. There's only that much technology can do.
 
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