Blackmagic Forum

I've just gotten my BMCC this week. Did not really got to shooting but just now and yesterday aswell I saw some very faint vertical lines in the footage.

So I grabbed a still from a DNxHD clip. It's most visible on the internal screen of the camera. I've tried pointing it to different surfaces and the vertical lines do not seem to move, like some sort of overlay/smear on the sensor.

However it's only visible when I point the camera on some lower lighted area's. And like I've seen in some DNG's that have the exposure lifted too much, the bottom half seems a bit darker and more pronounced in the lines.

The grabbed still doesn't really reflect it, I'll try and get some better footage that show it.

The question is, is this normal? Dimly lit wall near a lamp, not completely dark, because I know it's not a no-light camera.

Dropbox png still:

https://dl.dropboxusercontent.com/u/128 ... _1.3.2.png

Haven't done a thing to it in post.

to me it seems as if your iso-setting is simply too high..

NicoSchrenk wrote:to me it seems as if your iso-setting is simply too high..

It was @ 1600 ASA, however I do see it be it less pronounced on 800 asa and 400 asa aswell.

I was hoping to shoot @ 800 asa the whole time and expose with ND's but if 800 asa shows this kind of sensor pattern so fast I'm a tad sad.

please post DNG so we can see how the image was actually captured in RAW format.

Are you saying that you haven't boosted the exposure at all?

sean mclennan wrote:please post DNG so we can see how the image was actually captured in RAW format.

Are you saying that you haven't boosted the exposure at all?

I'll capture some raw footage shortly, this was from a DNxHD capture.

I hope you can either tell me there's something I'm doing wrong or that it is faulty.

https://dl.dropboxusercontent.com/u/128 ... 000815.dng

subject is just a white wall. Little light but no total darkness. Pattern remains mostly seen on the internal screen. Obviously more pronounced the higher the iso, but when i look very very closely it's visible at 400 asa aswell.

What ISO is this shot at? Man I hate how little info BMCC saves with DNG files.....

Really, it just looks badly unexposed. Shoot the same wall, at the same ISO, but change your shutter angle so it's properly exposed and let's see what that looks like.

sean mclennan wrote:What ISO is this shot at? Man I hate how little info BMCC saves with DNG files.....

Really, it just looks badly unexposed. Shoot the same wall, at the same ISO, but change your shutter angle so it's properly exposed and let's see what that looks like.

https://dl.dropboxusercontent.com/u/128 ... 000149.dng

800asa 360 shutter degree to brighten it up a little bit.

Just a white wall, darkened it with an ND filter.

Looks pretty artefact free to me.

http://tommajerski.com/publicimages/Blackmagic%20Cinema%20Camera_1_2013-08-27_1315_C0000_000149.png


If this is how it is at iso 800 - you are underexposing your image too far.

Might be something best seen on the run. Have you got a prores/dnx clip up anywhere?

MatthijsLiethof wrote:

sean mclennan wrote:What ISO is this shot at? Man I hate how little info BMCC saves with DNG files.....

Really, it just looks badly unexposed. Shoot the same wall, at the same ISO, but change your shutter angle so it's properly exposed and let's see what that looks like.

https://dl.dropboxusercontent.com/u/128 ... 000149.dng

800asa 360 shutter degree to brighten it up a little bit.

Just a white wall, darkened it with an ND filter.

Why are you underexposing the image so much? Can you just shoot the wall, at 800 ISO and get a proper exposure?

Just shot a practical light at ASA 800 and surfaces near the light had some light fall off and in there I could see the fixed noise pattern. Shadows where ok, totally black and the light was even having a center spot with zebras hitting 100% (i'll upload some dngs tomorrow)

Verstuurd van mijn HTC Sensation XE with Beats Audio Z715e met Tapatalk

https://dl.dropboxusercontent.com/u/128 ... _C0001.mov
https://dl.dropboxusercontent.com/u/128 ... _C0000.mov
https://dl.dropboxusercontent.com/u/128 ... 000252.dng


Again the footage looks so much darker than on the lcd screen of the blackmagic, I can't tell whats what.

On the BMCC screen the lines are very visible, here only when you put on a lot of gain.

Could it be the screen on my BMCC is just showing things wrong?

MatthijsLiethof wrote:Again the footage looks so much darker than on the lcd screen of the blackmagic, I can't tell whats what.

On the BMCC screen the lines are very visible, here only when you put on a lot of gain.

Could it be the screen on my BMCC is just showing things wrong?

Yes, the screen is only really a reference for composing your shots - not for exposing. Zebras can help to highlight clipping, but you're better off using a light meter or external monitor with a waveform or similar.

So the screen applies gain to the signal and makes it brighter then what I am really exposing it at?

MatthijsLiethof wrote:So the screen applies gain to the signal and makes it brighter then what I am really exposing it at?

The screen is not calibrated and so its reproduction of the recorded image will be differ to how it will likely look when your view your footage on your computer.

How's your screen? Surprising you aswell?

So a monitor that's on the SDI should show a better representation of the footage? (since you could record from sdi?)

And when I have a monitor with either waveforms or histograms, how do I know it's correct? (could be a stupid question)

Any monitors or EVF's that wouldn't be too close too a 1000 euro's and have those functions?


http://www.ebay.com/itm/Professional-Li ... 1144435985 something like this?

MatthijsLiethof wrote:How's your screen? Surprising you aswell?

So a monitor that's on the SDI should show a better representation of the footage? (since you could record from sdi?)

And when I have a monitor with either waveforms or histograms, how do I know it's correct? (could be a stupid question)

Any monitors or EVF's that wouldn't be too close too a 1000 euro's and have those functions?


http://www.ebay.com/itm/Professional-Li ... 1144435985 something like this?

My screen is not surprising me, I understand it is to be used only for composing a shot and as a reference as to what mode the camera is in.

So a monitor that's on the SDI should show a better representation of the footage? (since you could record from sdi?)

It depends on which monitor you get - in general it is not wise to expose based on the image alone, your eyes are not objective.

And when I have a monitor with either waveforms or histograms, how do I know it's correct? (could be a stupid question)

It will be correct assuming the SDI signal out is in "FILM" mode - which I think it has to be on the BMCC anyway.

Any monitors or EVF's that wouldn't be too close too a 1000 euro's and have those functions?


http://www.ebay.com/itm/Professional-Li ... 1144435985 something like this?

I can see it has false colour and histograms - but I cannot see a waveform - it depends on how you prefer to monitor, but I prefer a waveform over histogram.

False colour is pretty good though.

Why do you prefer waveform over the histogram? (easier to read?)

Would false color be a good subsitute for waveform or histograms?

Thanks for your time again, I really appreciate all the help I'm getting

MatthijsLiethof wrote:Why do you prefer waveform over the histogram? (easier to read?)

Would false color be a good subsitute for waveform or histograms?

Thanks for your time again, I really appreciate all the help I'm getting

It contains more detailed information and I find is easier to read.

Its no problem - It's my pleasure to help

I will say however that with the BMCC - it is very very easy to expose in raw mode. As our very own Frank always says - set your zebras to 100%, expose until just before clipping and pull down in post. Its fine to let specular highlights or minor light sources to clip - in favour of exposing for the majority of the field.

Does the same work with Prores or DNxHD?

Sent from my Android Phone

MatthijsLiethof wrote:Does the same work with Prores or DNxHD?

Sent from my Android Phone

no, the zebras at 100% will still show clipping, but with Prores or DNxHD you may aswell follow the same rules regarding when to clip or not clip -but then lower the iso to an approximate correct gamma point. This will result in the pull down occurring in camera rather than in post production.

So how do I approximate that gamma point? Just guess?



By the way, is there a reason the internal display is not calibrated?

Sent from my Android Phone

MatthijsLiethof wrote:So how do I approximate that gamma point? Just guess?



By the way, is there a reason the internal display is not calibrated?

Sent from my Android Phone

On board monitors on some cameras are even black and white - they are supposed to be used for composing a shot. To buy even a "cheap" colour reference monitor is several thousand dollars - let alone one small and touch sensitive and designed to fit inside a camera.

Even if the monitor was very very accurate and useful as a reference monitor - your eyes cannot see objectively and would not be a good way to check exposure. Reading a waveform or similar gives you the actual values and proper reliable data.

The zebras on the BMCC built in screen show sensor clipping - so the clipping point does not change depending on your iso. In non-raw modes, expose so that none of the vital parts of your image are clipping - then set your ISO to a comfortable viewing level. If it is slightly under, you can push it a bit in post, if it is slight over you can pull it back (the none clipped areas I mean). Other than this, you would be better using a light meter or external reference monitor with some kind of metering system.