Low-light sensor issue?

Hi everyone,

I was wondering whether the following is a sensor issue: I did a (very) low-light / exposure push test using an admittedly slow lens, 24-105mm F/4.0 L IS. When pushing the exposure of a DNG frame in post, there is a lot of noise, which is to be expected considering it's quite a large exposure push. However, it seems that on top of the noise, the bottom half of the image has a blue-ish tint? Surely that's not normal? (Please disregard the black bit at the top, that's my window frame).


http://imageshack.us/a/img40/5299/screenshot20130118at174.jpg



http://imageshack.us/a/img842/5299/screenshot20130118at174.jpg

I'v seen strange noise patterns, banding, etc... but tonight I will shoot a lot of low light scenes, with a 28mm f/2.8 lens and a 50mm f/1.4 lens... let's see...

I'v seen strange noise patterns, banding, etc... but tonight I will shoot a lot of low light scenes, with a 28mm f/2.8 lens and a 50mm f/1.4 lens... let's see...

I guess John Brawley was right to mention the BMCC was not a "low-light" camera. When there is enough light, the image looks absolutely stunning and I realise my test was very extreme and you wouldn't usually do this massive of an exposure pull in post, but the blue tinted bottom half also shows up in dark images when using a faster lens, rather than doing an exposure pull in post (it's even visible on the BMCC LCD screen)

There are also lots of stuck pixels (blue and white mostly it seems). It seems that you can take them out of the footage with chroma noise removal, but I thought the BMCC had a pixel remapping feature?

Frankly, I think you are pushing that a little beyond reason. You are bound to get all sorts of mess when you push an image past what the SNR can handle on any device. Small sensors will always perform worst in low light that larger sensors (of equal technology). There is only so much light they can absorb and signal booster, in any medium, sucks.

It's like driving your car in 6th gear while doing 20 mph and stating that the transmission is making funny noises and the acceleration isn't really as smooth as it is in 3rd. Can the car physically do it? Yes. Was it designed to do it? No.

That's the reason I never understood why Canon/Nikon included the ridiculously high ISOs on their cameras...everyone says the images are all but unusable, but it's cool they can shoot 200,000 ISO! um, no it isn't.

YMMV, but I don't see this as a severe limitation of the camera or anything. Nor do I think there is an issue with your camera, but I'm not BM. Have you sent the image to their tech support?

I'm also jealous you have yours

Here is a photo I have just taken with a Canon 5d Mkii.

IMG_4603.jpg (820.72 KiB) Viewed 1749 times

Using the exact same lens as you, at ISO 800, Raw mode, f4, 1/50 shutter

Boosted in photoshop without any NR or sharpening, (cropped to 2.4)


Look at the noise and the artefacts. It is perfectly normal. These are not night vision cameras. There is no low-light sensor issue. If you try to push the raw image too far when there is not enough light, you will see artefacts from every camera.

Hi, thanks for your responses.

I do realise that it's totally normal that there will be noise in the image (and in the image above I have actually removed chroma noise, which is why the noise still looks tons better than in the RAW 5D photograph you posted.)

However, it seems a little off to me that the blue artefacts are only present in the bottom of the image. It's impossible to get rid of with chroma noise reduction. The fact that it starts mid-way through the sensor/image reminds me of this guy's problem: http://www.bmcuser.com/showthread.php?1 ... ra-holders

Hi, thanks for your responses.

I do realise that it's totally normal that there will be noise in the image (and in the image above I have actually removed chroma noise, which is why the noise still looks tons better than in the RAW 5D photograph you posted.)

However, it seems a little off to me that the blue artefacts are only present in the bottom of the image. It's impossible to get rid of with chroma noise reduction. The fact that it's horizontally mid-way through the sensor/image reminds me of this guy's problem: http://www.bmcuser.com/showthread.php?1 ... ra-holders

Can you see the difference when shooting something with enough light? ie: normal conditions? If not, I wouldn't worry about it.

also, didnt you say back in sept that you hadn't pre-ordered yet.....


how did you get your camera already???

Can you see the difference when shooting something with enough light? ie: normal conditions? If not, I wouldn't worry about it.

I haven't used the camera much yet as I only got it today, but I have seen the issue in more normal conditions as well, in a dark area of the image. I doubt it will show up in daylight. I will keep testing and see whether it will be an issue or not.

also, didnt you say back in sept that you hadn't pre-ordered yet..... how did you get your camera already???

I bought it off someone who ordered the camera back in April. He is abroad for half a year and "exporting" the camera would have been too expensive, so I paid him and he had CVP send it to my address instead.

^^^^ LOL, yeah! Enquiring minds want to know