High ISO magenta noise

Hi,

does anyone experience high ISO magenta noise on Nikon D750? What does it cause? On my D750 rear display, the magenta noise starts showing up from about ISO 5000 along bottom of the frame and in the bottom left corner of the frame so the camera is not useful for photography from ISO 5000 up. Big disappointment.

Petr

petr said:

Hi,

does anyone experience high ISO magenta noise on Nikon D750? What does it cause? On my D750 rear display, the magenta noise starts showing up from about ISO 5000 along bottom of the frame and in the bottom left corner of the frame so the camera is not useful for photography from ISO 5000 up. Big disappointment.

Petr

Click to expand...

Could you post an example photo or two that shows this? I've shot at much higher ISO on my D750 and I've never noticed this issue.

petr said:

Hi,

does anyone experience high ISO magenta noise on Nikon D750? What does it cause? On my D750 rear display, the magenta noise starts showing up from about ISO 5000 along bottom of the frame and in the bottom left corner of the frame so the camera is not useful for photography from ISO 5000 up. Big disappointment.

Petr

Click to expand...

Please post a shot with the said problem that you are experiencing. Also which lens are you using? You might be mistaking CA with noise.

You say your seeing it on your rear display,is it in the images or just on the display.

The only time I have seen that problem is when I severally underexpose a shot. Proper exposure at a higher ISO shoud take care of the problem I have shot at ISO 12,500 a number of times without any problems.

Magenta noise can occur when seriously underexposing; it's the loss of channels which translates in such colors. It's clipping by being pushed too far. It can be fixed in post using something like color balance.

You occasionally see it at the LCD too but one has to keep in mind that your LCD only displays 8-bit and not what the RAW truly captures.

Here's a shot taken suffering clipping:





It suffers the magenta "noise" too even while being shot at 100 ISO.

Hi everybody and thanx for your replies, to J-see especially. Yes, the magenta high ISO noise is in the pictures, not only on the rear display. Interestingly, the noise on the rear display is much more vivid then in the pictures. Usually I test the presence of the magenta noise in the photo by making an exposure with the lens cup on. Every exposure taken like this with ISO number from 5000 up shows the magenta noise, the higher ISO setting the stronger magenta noise. I hate to have found it out after purchasing the camera. Is it a normal phenomenon with all DSLRs of all makers including the most expensive top pro full frame cameras? Or should I have mine got serviced? Before purchasing my Nikon D750, I went through many reviews of the camera and its competitors and never hit a word about this annoying artefact. See this example of the night photo taken by my D750 at ISO 12800-f2.8-1/10s:

I get the feeling you may be missing the point,its only there with incorrect exposure,i dont have a 750 now but this was 11400 iso

Just to reiterate what @mikew said... Here's a shot (with lots of deep shadow) I took with my D750 a while back, also shot at ISO 11,400. No no noise reduction was done:
....
.....

I just checked out the shot with the lenscap on. I used some blending and brightness adjustment to show better what should not be there.



Try taking the same shot but with the viewfinder covered since it can leak light through there. If you still get the same noise, something weird is going on.

Edit: I pushed it even more.



That there is a pixel active here and there I can imagine but this is something else. Either light leaks in, the sensor "misbehaves" or amplification goes wrong.

Also try a shot at 100 ISO with the cap on.

Thank you for your cooperation with this problem J-see. I've already tested taking a picture with the lens cup on and the viewfinder cover on as well. The result is exatly the same - the magenta noise along the bottom of the picture. Don't please tell me that my camera is affected with some technological or technical problem as this Nikon model unfamously experienced twice since the beginning of its production. Petr.

It looks like you got some serious issue but what exactly might be harder to figure out. I have taken some 30k shot with mine but this I've never experienced.

If it only shows at higher ISO, I'd gamble on the amplification but whatever it is, better ship it to the shop.

As I already mentioned, from ISO 100 to about ISO 5000 there is no magenta noise in the frame (both with or without the lens cap on). You people never had this kind of weird noise at high ISOs?

petr said:

As I already mentioned, from ISO 100 to about ISO 5000 there is no magenta noise in the frame (both with or without the lens cap on). You people never had this kind of weird noise at high ISOs?

Click to expand...

In short, no.

I'd still like to see a shot that shows the problem.

petr said:

As I already mentioned, from ISO 100 to about ISO 5000 there is no magenta noise in the frame (both with or without the lens cap on). You people never had this kind of weird noise at high ISOs?

Click to expand...

Nope, this is new to me.

I checked the difference between 6400 and 12k ISO and it clearly increases as the ISO goes up. It starts at the bottom corner and slowly works its way up to the opposite corner. It's possible the problem already exists at 100 ISO but because the signal isn't amplified as much, the difference remains too small to be seen.

Horoscope Fish said:

In short, no.

I'd still like to see a shot that shows the problem.

Click to expand...

Here's that shot he shared; I upped brightness a bit:



Some more:

Well guys, I'm going to the photocamera shop with my high ISO issue next week I guess.

J-see said:

Here's that shot he shared; I upped brightness a bit: ... Some more:

Click to expand...

That's a problem alright.

Oh my G. I tried to turn off the Active D-Lighting mode that was set to Normal level...and guess what...the high ISO magenta noise in the exposed pictures disappeared right away! Well, I am now going to read again my D750 User's Manual to find out when to use ADL and when not. Jeee...

And here it is - page 176:
Active D-Lighting Noise (randomly-spaced bright pixels, fog, or lines) may appear inphotographs taken with Active D-Lighting. With some subjects, youmay notice uneven shading, shadows around bright objects, or halosaround dark objects.




Typical beginner's fault :stupid: